What Size Tankless Water Heater For 2 Bathrooms?

What Size Tankless Water Heater Do I Need? (For Family Of 2,3,4,5,6)

An expensive tankless water heater that is not powerful enough to meet our demands is one of the most common blunders people make when purchasing a tankless water heater.Tankless heaters should not be purchased based on their size.Neither should they be purchased based on their size, since this will waste energy.The size of your tankless water heater should be as close to your household’s hot water requirements as feasible.

In what size tankless water heater do I need to invest my money?In order to determine how many GPM tankless water heaters I require for the gas unit and how many kW I require for the electric unit, I must first determine how many GPM tankless water heaters I require for the gas unit.Here’s how it works: Before you can accurately answer the question of what size tankless water heater you require, you must first determine two things:

  1. What is the greatest amount of hot water you require?
  2. What is the maximum amount of water per minute (measured in Gallons Per Minute or GPM) that a particular tankless water heater can heat, and by how many degrees?

It is necessary to establish a preliminary estimate of our maximal hot water requirements at any given point in order to properly design the tankless water heater.From 9 p.m.to 11 p.m., most families have the greatest demand for hot water.That is the time of day when we shower, brush our teeth under a hot faucet, and perhaps even have the dishwasher on.

We need to keep track of how much hot water we’re using.Here’s a handy table that shows how many GPMs are required by different types of water fixtures:

Fixture Gallons Per Minute (GPM)
Shower 2.0 – 3.0 GPM
Faucet (kitchen, bathroom) 1.0 – 2.0 GPM
Dishwasher 1.5 – 2.0 GPM
Washing Machine 2.0 – 2.5 GPM

For example, if you’re taking a shower (with 100 percent flow and 110°F hot water) and concurrently using two faucets (both with 100 percent flow and 110°F hot water), you’ll need a tankless water heater with at least 5 GPM flow rate.It is possible to get anything from 2 GPM to 12 GPM of hot water using a tankless heater.How many gallons per minute do you require?The ones with a flow rate of 5-10 GPM are the most suitable for the majority of houses.

As previously stated, the cost of a tankless water heater grows in direct proportion to the capacity of the unit.It should be noted that electric tankless hot water heaters are suited for modest water demands up to 8 GPM.Choosing one of the top gas tankless hot water heaters from this list is recommended for larger requirements (8 GPM or more).

Difference Between Maximum Water Flow And Realistic Maximum GMPs

When comparing the specifications of different tankless heaters, you will see that they all list the maximum GPMs.When it comes down to it, the highest GMP that your tankless heater will truly reach might be far lower.What is the source of the discrepancy?Because the maximum water flow in GMP is calculated by heating water to 77 degrees Fahrenheit, The inlet temperature of the water that is currently in your pipes is quite important.

For example, in south Texas, the inflow water temperature is 77 degrees Fahrenheit.In Minnesota, for example, the temperature of the input water might be as low as 37 degrees Fahrenheit.That represents an additional 40 degrees Fahrenheit differential that a tankless water heater must overcome.

  1. Calculation in a few words: Consider the following scenario: we have a tankless heater with a maximum water flow of 10 GPM.
  2. Because the input temperature is 77 degrees Fahrenheit in Texas, we can really obtain 10 GPM of 110 degrees Fahrenheit water.
  3. The heater must heat water from 77 degrees Fahrenheit to 110 degrees Fahrenheit, a difference of 33 degrees Fahrenheit.
  4. In Minnesota, on the other hand, the inlet water temperature is 37 degrees Fahrenheit.
  5. In order to heat water to 110 degrees Fahrenheit in Minnesota, a tankless heater must overcome a temperature differential of 73 degrees Fahrenheit, rather than the 33 degrees Fahrenheit difference in Texas.
  6. You don’t come from Minnesota or Texas, do you?

Here’s an infographic developed for the Rinnai RU160iP SE+ Series 9 GPM tankless water heater that will give you an idea of what the maximum water flow rate is in your state (legal for the United States of America).An additional example based on the infographics shown above is as follows: If you reside in Florida (inlet temperature of 77 degrees Fahrenheit), the Rinnai RU160iP SE+ Series tankless heater will have a maximum water flow of 7.1 GPM at its maximum temperature.The water pressure is sufficient to run numerous showers at the same time.

If you reside in New York, on the other hand (with an intake temperature of 52 degrees Fahrenheit), the same tankless water heater may deliver a maximum water flow of 4.5 GMP.That is a direct outcome of the temperature differential between the input and outlet.In New York, the heater must contend with an additional 25 degrees Fahrenheit.

  • You will be able to operate two or three showers at the same time using the same heater and the same amount of energy consumption.
  • It’s important to consider the operating costs as well, especially with larger units.
  • You can find out how much power larger electric tankless water heaters consume by visiting this page.
  • The amount of propane that these on-demand hot water heaters consume is another useful piece of information regarding propane units to read.

What Size Tankless Water Heater Do I Need For A Family Of 2, 3, 4, 5, Or 6?

When it comes to tankless water heater sizing, one of the most often asked topics is how much of a unit you need for a household of multiple people.Obviously, a tankless water heater designed for a family of three will be smaller than one designed for a family of five.But what are the specific GPM (for gas-powered engines) or kW (for electric-powered engines) figures?Because of the changing temperature of the water entering the tankless hot water heater, determining the correct size of the tankless hot water heater is difficult.

A table containing estimations may be seen below.Unfortunately, the confidence ranges are extremely wide.Those in the Northern United States will require larger units than homes in the Southern United States, for example, as follows:

Number Of Family Members: Gas Tankless Heater Size (GPM) Electric Tankless Heater Size (kW)
What size tankless water heater do I need for a family of 2? 6-8 GPM 10-18 kW
What size tankless water heater do I need for a family of 3? 7-9 GPM 15-23 kW
What size tankless water heater do I need for a family of 4? 8-10 GPM 20-28 kW
What size tankless water heater do I need for a family of 5? 9-11 GPM 25-34 kW
What size tankless water heater do I need for a family of 6? 11+ GPM 34+ kW

These data are provided just as a point of reference. The size of your tankless water heater is determined by a number of crucial criteria, such as the temperature of the water entering the tank and the amount of hot water you use on a regular basis.

Looking At Specifications Sheets

It is common to find manufacturers specifying a maximum water flow number in GMP or a maximum electric power number in kW on specification documents for their products.The GMP number for gas-powered tankless water heaters is often found on the product label, whereas the kW number for electric tankless water heaters is found on the product label.As we’ve shown, the maximum GMP is a function of context.It is dependent on where you live in the United States (because that affects the inlet water temperature).

Power, on the other hand (measured in kW), is absolute.Comparing the maximum wattage of different tankless heaters (as we have done in the table of the best tankless heaters below) allows us to determine how powerful they are in comparison.All things considered, you must also consider certain financial calculations, for example.

  1. It is advised that you check here to see if a tankless water heater is actually worth the investment (we did some calculations).
  2. Let’s take a look at two real-life situations.
  3. For example, if you want to replace your current 50-gallon water heater, the first question you should ask is what size tankless water heater you need.
  4. Second, the number of people who live (and utilize) hot water in your home is taken into consideration.
  5. What size tankless water heater would be appropriate for a household of five, for example.

What Size Tankless Water Heater Do I Need To Replace A 50 Gallon Water Heater? (Example1)

  • Here’s how things work in this situation: You now have a tank-style water heater that holds 30, 40, 50, or even 80 gallons of water and wish to upgrade to a tankless water heater. The most significant distinction, of course, is that a water tank provides, say, 50 gallons of hot water, but a tankless water heater provides water heating on demand. For example, during a typical 10-minute shower, you use around 10 gallons of hot water on average. Taking 3 showers, running a few of faucets, running a dishwasher, and so on will easily deplete those 50 gallons in no time. When it comes to tankless water heaters, though, things are a little different. Instead of storing hot water, the tankless heater’s strong heating exchanger warms the water as it is needed, up to a particular maximum GMP limit, depending on the model. You would, roughly speaking, require the following items to replace a 50-gallon water heater: a 10 GPM gas tankless heater or at least a 27 kW electric tankless water heater if you live in the northern part of the United States
  • a 7 GPM gas tankless heater or at least an 18 kW electric tankless water heater in the southern part of the United States
  • and a 50-gallon water heater replacement kit.

As a result, Rinnai, the world’s leading manufacturer of gas tankless heaters, provides a broad range of models ranging from 7 GPM to 11 GPM: Please keep in mind that this is simply an approximate estimation. The prudent course of action is to get a tankless heater that is somewhat more powerful than the anticipated need. It is preferable to be safe than sorry.

What Size Tankless Water Heater Do I Need For A Family Of 5? (Example2)

If five individuals reside in the same house, they can use multiple faucets or showers at the same time.This must be taken into consideration while determining the appropriate size of a tankless water heater.Showers are the home hot water user that consumes the most hot water the fastest.5 persons can also operate many hot water taps at the same time, as well as a dishwasher and do laundry, among other things.

In summary, if you live in the northern portion of the United States, where the input water temperature is lower, you would require a 10 GPM gas tankless heater or a 27 kW electric tankless heater.The tankless heater needs to work extra hard to raise the water temperature to 110°F or 120°F, depending on the situation.For those who reside in the southern part of the country, the tankless water heater’s capacity might be lowered by up to 30 percent.

  1. As a result, for a family of five in the southern United States, a 7 GPM gas tankless heater or an 18 kW tankless heater should be more than adequate to meet all of their hot water demands.
  2. Keep in mind that, especially with larger units, tankless water heater circulation pumps can save you a significant amount of money on hot water.
  3. These pumps come in handy when you need hot water from a faucet or shower in a short amount of time.
  4. You won’t have to wait for hot water to start flowing, squandering all of the cold water that would have been wasted in the meanwhile.

How Many Tankless Heaters Do I Need?

This is a rather typical topic, especially when it comes to larger homes.Here’s how it works: In the majority of situations, one tankless heater is sufficient to heat an entire house.For those who live in really large homes (2 or more bathrooms), even the largest Rinnai gas tankless water heater with a flow rate of 11 GPM will not be adequate to meet all of their simultaneous hot water demands.It makes logical in these situations to install two tankless water heaters.The most common combination is as follows: The largest gas unit (11 GPM, 199,000 BTU) and the largest electric unit The large tankless water heater meets the majority of the household’s hot water requirements.During times when we require a large volume of hot water, the electric tankless water heater is activated to provide assistance.

Alternatively, you might utilize two units for different parts of the home, one for one section and another for the other section of the house.Specifically, the plumbing for each units is separate in this instance.I hope this has been of assistance.

What Size Tankless Water Heater For Two Bathrooms? – Bathroom

| July 22, 2021 10:33 a.m. | Bathroom | Sariah Berg provided the answer.

Rheem Tankless Water Heater Installation Part 1: sizing, buying and hanging

Tankless Water Heaters (COMPLETE GUIDE) | GOT2LEARN

Can a Tankless Water Heater Support a Large Family?

Frequently Asked Questions

What size water heater do I need for 2 bathrooms?

30-40 gallons of water for 1 to 2 persons. 40-50 gallons of water for 2 to 3 persons. For a family of three or four persons, 50-60 gallons is plenty. For a family of five or more persons, 60-80 gallons is recommended.

Can two people shower at the same time with a tankless water heater?

However, when correctly scaled, a tankless water heater can cover all of a household’s hot-water requirements, including those from numerous showers that are running at the same time while everyone gets ready for the day.

What size tankless water heater do I need for a family of 7?

What size tankless water heater do I require for a family of two, three, four, five, or six people? The number of family members is as follows: Gas The Dimensions of a Tankless Heater (GPM) The Dimensions of an Electric Tankless Heater (kW)

What size tankless water heater do I need for a family of 2? 6-8 GPM 10-18 kW
What size tankless water heater do I need for a family of 3? 7-9 GPM 15-23 kW

3 more rows

Can a tankless water heater be used in a low flow shower?

Modern low-flow showerheads deliver the same water pressure and shower experience as higher-flow ones without sacrificing any of the benefits of the latter. However, there is a disadvantage to using these showerheads. Because tankless water heaters have variable activation flow rates, if the flow rate is too low, the tankless water heater may not be triggered.

How big is a Bosch tankless water heater?

When using an earlier model shower head (pre-1992), the flow rate can be as high as 6 to 8 gallons per minute (GPM). A shower head installed after 1992 will typically utilize 2.2 GPM of water. However, let’s pretend that the Bosch 1600P-NG tankless water heater is just being utilized as a supplemental water heater in this scenario. What about the company’s claim of 4 GPM?

How to Select the Right Size Tankless Water Heater

Tankless water heaters are classified according to the highest temperature rise that may be achieved at a given flow rate.For this reason, in order to calculate the appropriate size of a demand water heater for your home, you must first estimate the flow rate and temperature increase that will be required for its application (either the entire house or a distant use, such as a bathroom).It is vital to note that you should never attempt to save money by purchasing a tankless water heater that is undersized.

See also:  How To Turn Up Heat On Water Heater

Step 1:

Make a decision on the maximum number of devices that you wish to run and the overall flow rate of those devices.Then total their flow rates together (gallons per minute).This is the intended flow rate that you’ll need for the demand water heater that you’ve purchased.Consider the following scenario: you anticipate to be able to operate a hot water faucet with a flow rate of 0.75 gallons per minute while also running a shower head with a flow rate of 2.6 gallons per minute concurrently.It would be necessary for the flow rate via the demand water heater to be at least 3.26 gallons per minute.Installing low-flow water fixtures can help to lower flow rates.

Step 2:

Calculate the temperature rise that is necessary.To calculate the temperature rise, subtract the entering water temperature from the desired output temperature and multiply by 100.Assume that the incoming water temperature is 50 degrees Fahrenheit unless you know better.You may rest assured that you will not undersize your tankless unit if you use the low temperature assumption).If you reside in a warm climate, the temperature of your water will most likely be significantly higher.For the majority of applications, water should be heated to around 105–115°.

A demand water heater that delivers a temperature increase of 55° would be required in this scenario.

Step 3:

Example of sizing: An typical shower will be between 104 and 106 degrees Fahrenheit and utilize 2.6 gallons of water.Assuming that the water temperature entering your home is 40° and that you wish to create enough hot water to run two showers at the same time, what temperature rise would you need to produce to achieve this goal?Answer: You’ll need to boost the temperature of the entering water from 40 degrees to 105 degrees.The ability to heat a minimum of 5.2 gallon of water will be necessary.As a result, you’ll need a tankless water heater that can provide at least a 60-degree increase in temperature while also dispensing 5.2 gallons per minute of water.

Flow Rates

Is there a limit to how much hot water you may use at once?You need to operate two showers at the same time, or a shower and a pair of sinks, or anything similar.The figure below illustrates the range of water consumption ranges as well as the typical water temperatures for a variety of fixtures.In order to determine your total simultaneous water requirements, we recommend that you use the following reference points: 2.5 gpm for showers and 1.0 gpm for bathrooms.


Average Flow GPM

Average Temp.

Tub 4.0 GPM 102°F
Shower 2.5 – 3.0 GPM 104°F
Washing Machine 2.0 GPM 120°F
Dishwasher 1.5 GPM 110°F
Kitchen Sink 1.5 GPM 110°F

Consider the following scenario: If you are taking two showers at the same time, you will require 5 gallons of hot water per minute from your tankless water heater.A shower and the washing machine would each use 4.5 gallons of water per minute from the water heater, thus you would need to turn on both at the same time.In any of these scenarios, you’ll want to make sure that the unit you choose is large enough to accommodate or surpass the amount of hot water you’ll require at the same time.It is important to note that tankless water heaters are only designed to heat potable (drinking) water, and that the water entering a tankless device should not be pre-heated before use.

Other Sizing Notes

Gas tankless water heaters have the ability to create a greater temperature rise per gallon of water than electric tankless water heaters.The majority of demand water heaters are rated for a wide range of water temperature inputs.An average flow rate of 5 gallons per minute via gas-fired demand water heaters and a flow rate of 2 gallons per minute through electric demand water heaters will result in a 70°F increase in water temperature in most cases.Increased flow rates or decreased intake temperatures can occasionally result in a reduction in the temperature of the water at the furthest faucet.

Recommended Reading:

  • Learn how to use a washer dryer combo
  • learn about three common misconceptions about washer dryer combos
  • learn all you need to know about wall heaters in this comprehensive guide
  • and more.
  • Infrared Heaters 101: Your Complete Guide to Understanding Them

About Our Team

Jeff Flowers is just a person who is plagued by a chronic case of curiosity and who frustrates everyone around him with his rambling nonsense.In his journey from beer to house living, Jeff is simply attempting to hack his way through life while also writing a few notes about his experiences along the way.Alternatively, you can listen to him rant about Austin traffic on Twitter at @Bukowsky, where you can follow his musings as well.

How To Size A Tankless Water Heater

If you are in the market for a new water heater, tankless hot water heaters may be an option to investigate. This type of hot water heater may provide you with a number of various advantages. In addition, you will need to understand how to properly size a tankless water heater.

What Is A Tankless Hot Water Heater?

It is a type of water heater that does not contain a storage tank, as opposed to standard water heaters.As soon as you turn on your faucet, cold water is instantly turned to hot water, and vice versa.You will save money on your utility costs because, unlike standard water heaters, you will not be required to heat the water on a continuous basis.Tankless water heaters are also more space-efficient than typical water heaters, taking up significantly less space.

Sizing Your Water Heater

You will need to determine the appropriate size of your water heater.If you choose the incorrect size, it may not be able to adequately heat the water in your house.Particularly problematic is the situation in which you are attempting to utilize various restrooms or appliances at the same time.It is possible to determine How To Size A Tankless Water Heater by following the methods outlined below: Step 1: Take some time to sit down and figure out how many devices you’ll need to have hot water for, as well as the flow rate for each.The flow rate is the number of gallons per minute of water flow that you will require.If you want to run your shower and faucet at the same time, you’ll need to figure out how much water each of them can handle.

When it comes to hot water faucets, a flow rate of around 0.75 gallons per minute is recommended.The flow rate of the shower head will be 2.6 gallons per minute.Your hot water heater should be able to deliver at least 3.26 gallons of hot water per minute, whichever is higher.Low-flow water faucets and shower heads are available for purchase and installation if you wish to reduce your flow rates.

  1. 2.
  2. Determine the temperature rise that will be required for your equipment in step two of this procedure.
  3. You will need to subtract the temperature of the incoming water from the temperature of the output water.

If you do not know the exact temperature of your entering water, you should always presume that it is 50°F or above.This will assist to guarantee that you do not choose a tankless hot water heater that is too small.It is crucial to understand that if you reside in a hotter climate, the temperature of your entering water will be greater.You will want to choose a temperature range of 105 to 115 degrees.

If this is the case, you will need to ensure that the tankless water heater has the ability to offer a temperature rise of 55 degrees or greater.

Sizing Example

You will need to have a shower temperature of between 104 and 106 degrees to get the most out of it.When you take a shower, it will use 2.6 gallons of water every minute.A minimum of a 60-degree increase in temperature is required, and your tankless hot water heater should be capable of producing 5.2 gallons per minute in order to guarantee that you have the appropriate water temperature.You will need to pay close attention to this since sizing your system incorrectly can result in you not having enough hot water to complete the tasks that you need to do.Determine the flow rates that you will require from your hot water heater in order to guarantee that you can complete the tasks that you have set for yourself.Suppose you want to take two showers at the same time, or you want to run many sinks at the same time.

In order to meet your bathroom water requirements, it is advised that you utilize 1.0 GPM.The water from your tankless water heater will be insufficient if you are running two different showers at the same time.Water consumption will be around 4.5 gallons per minute if you need to operate both your washing machine and shower at the same time.You’ll want to be certain that the heater you choose is the appropriate size.

  1. Calculating your water use rates can assist you in selecting the most appropriate tankless water heater for your needs.
  2. If you want a higher temperature rise per GPM of water, you may want to look into buying a gas tankless hot water system here.
  3. These gas hot water heaters have the ability to swiftly raise the temperature of the water.

For more information on How To Size A Tankless Water Heater, contact the Original Plumber right away.They will be able to tell you what size water heater you require and will show you the many alternatives that are available.They may sit down with you and go through your use rates to evaluate if it would be more cost effective for you to purchase an electric tankless hot water heater or a gas tankless hot water heater.Hiring a professional plumbing firm eliminates the need to worry about the installation of the hot water heater or ensuring that you have the proper size.

The installation of a water heater may be complex and risky, therefore it is always a good idea to leave it to the experts.

Tankless Water Heater Buyer’s Guide


A tankless water heater, which may be installed on the wall of your garage, utility room, or even outside your home, can provide hot water for your whole home, from taps and showers to soaking tubs, dishwashers, laundry, and other appliances.Tankless water heaters provide hot water on demand, which means that assuming you install a properly sized unit, you will be able to have hot water whenever you need it, in as many locations as you need it, for as long as you need it.Tankless water heaters are ideal for small to medium-sized households.In reality, these are two of the most significant advantages of tankless water heaters: they save space and money.There are two advantages to using solar hot water: 1) you don’t have to waste energy continuously keeping a large volume of water hot, and 2) you can generate an unlimited flow of hot water, so you don’t have to worry about running out of hot water during a long shower or filling a soaking tub completely.


The three types of tankless units now available on the market are non-condensing, condensing, and hybrid condensing.Non-condensing tankless units are the most common.The essential principle for all three is the same even if they work in a somewhat different manner.When you switch on the faucet, a gas burner ignites and a heat exchanger coil transfers heat to the incoming cold water flowing through the coil, resulting in hot water being delivered to your faucet through the faucet.Electric tankless heaters that use elements instead of a gas burner are also available, although they are not as effective at heating a complete house as gas tankless heaters.It takes a large amount of gas to heat the water to a proper temperature, often between 150,000 and 200,000 BTUs, which means that most homes will require an upgrade in the size of their gas line.

With a condensing tankless water heater, you can take things one step further by incorporating a second heat exchanger to take use of extra exhaust heat, which allows you to heat your water even more efficiently while also lowering your running costs.A modest reservoir of 2 or more gallons is included in a hybrid tankless water heater to compensate for ″short draws,″ which are hot water requirements that do not require a large amount of hot water, such as hand washing.Maintaining a full supply of hot water in this little tank keeps the unit from having to fully fire up, increasing its overall efficiency.It is important to remember that tankless water heaters do not technically produce ″instant hot water,″ since hot water must still be allowed to flow from the unit to the faucet.


For homeowners who presently have a traditional tank water heater and are wanting to replace it because their existing tank is outdated, inefficient, and/or leaking water, a tankless water heater is an excellent option.Other people move to tankless water heaters simply because they wish to minimize their annual water heating expenditures and/or have access to unlimited hot water.Despite the fact that tankless water heaters have been in use in Europe and Asia for more than two decades, they are only now beginning to achieve widespread acceptance and use in the United States of America.Tankless water heaters are becoming increasingly popular for a variety of reasons, including the fact that they save valuable floor space in your garage or utility room, that they last 20-30 years because they are less susceptible to rust and leaks, that they can increase the resale value of your home, and that they are 40-50 percent more efficient than traditional tank water heaters.When compared to a typical gas tank water heater, which costs an average household around $250 per year to heat water, a tankless water heater may save an average household $75-$120 per year.Whether you’re worried about the environmental effect of your water heater or just want to reduce the expense of heating your water, a tankless water heater is a winner in both areas.

Installation of a tankless water heater may potentially result in a refund from your utility company.product of superior quality and durability In addition, new federal laws governing water heaters, which are set to take effect in 2015, should be taken into consideration.If you have a gas water heater that holds more than 55 gallons, you will be forced to replace it with a water heater that has an efficiency rating of at least 82 percent starting in 2015.Tankless water heaters and condensing tank water heaters, both of which are more unusual and less well-tested, are the only products that receive this grade.


  • Hot water will never run out since a tankless unit heats on demand, thus there will be no shortage of hot water. Large families or residences with high hot water demands, such as those with a soaking tub or spa system, might benefit from a tankless water heater. A tankless water heater is a great option if you’re thinking about upgrading your tank from 40 or 50 gallon capacity to 66 or 80 gallon capacity or if you’re replacing an older, bigger tank.
  • It conserves space: The tankless unit has a significantly smaller footprint, which allows for more precious storage space in the home or garage.
  • Efficiencies in terms of energy: The most efficient standard gas tanks presently run at 62-67 percent efficiency, compared to 82-96 percent efficiency for today’s tankless water heaters, resulting in yearly savings of around $100 for the majority of households.
  • Tankless units have a longer lifespan and can survive up to twice as long as regular tanks, according to industry standards. You will have to replace your tankless unit half as often as you would your tank, which is a significant savings.
  • Increasing the selling value of your property: In certain situations, homeowners may be able to recoup the cost of a tankless water heater installation since a tankless water heater may enhance the sale value of your home.
  • A tankless unit conversion can be prohibitively expensive, with the entire cost of a job often ranging from $2,000 to $4,500 installed owing to the addition of gas lines and venting, as well as the installation of new water lines. Fortunately, because these retrofit expenditures will not be incurred during your future tankless installation, your next tankless installation will be substantially less expensive.
  • Waiting time at the faucet has increased: Installing a tankless water heater, in the opinion of many homeowners, will shorten the amount of time it takes for water to get hot at the tap. This is not true – in fact, in most circumstances, a tankless water heater will require around 15 seconds longer to provide hot water to the faucet.
  • It is not assured that lower operating expenses will be achieved: Some homes will consume significantly more hot water on a regular basis as a result of being able to get unlimited hot water on demand. This additional demand might cancel out the savings in power expenses that result from the installation of a more energy-efficient tankless water heater.
  • Electricity is required for tankless units: The fact that tankless water heaters rely on electricity means that they will not be able to supply hot water in the case of a power outage
See also:  How Much Does It Cost To Install Hot Water Heater

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What is a flow rate, and what should I ask for when I want one?The gallon capacity, recovery rate, and first-hour rating of standard hot water tanks are all considered when comparing them, whereas the per-minute flow rate of tankless water heaters is considered when comparing them.In most cases, flow rates range between 4 and 12 gallons per minute for most main brands (GPM).Consider the following typical hot water requirements, as well as the flow rate requirements for each:

Dishwasher 0.5 – 1.0 GPM
Bathroom sink 0.5 – 1.5 GPM
Kitchen sink 1.5 – 2.0 GPM
Utility sink 1.5 – 2.0 GPM
Washing Machine 2.0 – 2.5 GPM
Shower 1.5 – 2.5 GPM
Bath tub 2.5 –.0 GPM
Jacuzzi/Hot tub 4.0 – 5.0 GPM

Consider how many of these requirements you could have at the same time in order to establish the maximum flow rate you’ll need.We recommend 6-7 GPM for a home with one bathroom; 8 – 9 GPM for a home with two bathrooms; and 9-11 GPM for a home with three or more bathrooms.Our experience has shown that units with a flow rate of 4-5 GPM are acceptable for studio flats, one-bedroom houses, and other application-specific requirements.There are further solutions available for really big homes, including the installation of numerous tankless units in series.What is temperature increase, and how does it influence my decision on the maximum GPM?Depending on where you reside, the temperature of the water entering your home varies significantly.

If you reside in the northern United States, your typical winter water temperature is 40-50 degrees Fahrenheit.If you reside in the southern United States, the typical winter water temperature is 50-65 degrees Fahrenheit.What location do I want my tankless water heater to be installed?When converting to a tankless water heater, many homeowners choose to move their existing water heater.

  1. Consider where you want to put your water heater, since there are both indoor and outdoor models available on the market these days.
  2. Installation of outdoor units is often less expensive than that of inside units.
  3. The Efficiency Factor (EF) is a measure of how efficient a system is.

The higher the efficiency factor (EF), the less it will cost to operate the tankless water heater.The efficiency of a heat transfer system measures the amount of heat transferred from an energy source to your hot water.An EF of.92 –.96 indicates that the finest tankless water heaters are 92–96 percent efficient, which suggests that they are cost-effective.What brand should I go with, and why?

When selecting a tankless water heater brand, it is important to evaluate the warranty, the availability of local service providers, and the dependability of the product.In the case that your water heater has to be maintained, check to see if there are any installers in your region that are qualified to operate on the particular device.


When selecting a tankless water heater, the two most significant factors to consider are the following:

Fuel type:

A gas tankless water heater (natural gas or propane) can be installed in place of an existing gas tank water heater (either natural gas or propane).In order to service the high needs of tankless systems, which may reach up to 200,000 BTUs, you will almost certainly need to upgrade the gas line running from your meter to your heater.Existing electric water heaters will need to be replaced with gas or propane water heaters, or a gas connection will need to be added in order for the water heater to function properly.It is possible to receive considerable rebates from some utility providers when converting from electric water heating to gas water heating.Switching to gas tankless water heating is an excellent decision and an excellent chance to take advantage of these rebates.As a result of the poor feedback, less-than-desirable temperature and flow characteristics of electric tankless water heaters, we do not recommend them for most whole-home water heating applications.


It is critical to choose the most appropriate location for your tankless water heater in order to maximize space savings while also minimizing installation expenses.Consult with your installer to determine the most convenient location for a tankless water heater in your house.You should also consider the fact that the machine will require dedicated electricity.Take note that in the event of a power failure, the device will not be able to supply hot water.Installers, on the other hand, can add a backup battery system if you so choose.The current plumbing rules and permit charges should be discussed with you by your installer before they begin work on your tankless water heater installation project in order to estimate the overall cost of the project.

Make certain you understand the standards in order to ensure that your water heater is installed properly.Additionally, request that your installation assist you in understanding the periodic maintenance requirements of a tankless water heater.Although low maintenance expenses are associated with this product, some manufacturers prescribe a descaling procedure, the frequency of which will be determined by the quality of the water available in your area.This will assist you in extending the life of your tank.

  1. Additional advice and recommendations can be found in your owner’s handbook.


Some utility providers provide incentives to customers who purchase and install a tankless water heater, therefore lowering the initial out-of-pocket costs.Call your utility provider to learn about incentives that are available in your region, or visit our rebates & incentives page for more information.Get in touch with Fast Water Heater Co.RIGHT NOW if you want more information about tankless water heaters.

Call (425) 636-7038 for fast service

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Do Tankless Water Heaters Run Out of Hot Water?

When it comes to installing water heaters in Clovis, NM, we are strong proponents of the latest technological advancements available.The most recent technological advancements in storage tank water heaters have made them more energy-efficient than ever before.However, we frequently advise homeowners to experiment with different types of water heater technologies in order to take advantage of innovative means of heating water, such as a heat pump water heater, which draws heat from the surrounding air to warm the water.The tankless water heater is something we’re very thrilled about.However, while tankless water heaters have been around since the late 1900s, it is only recently that technology has advanced to the point where they are a viable and cheap alternative for homeowners.When individuals learn about the advantages of these water heaters, they are frequently enthused by the possibilities that they present.

We’d like to focus on one of those advantages, the one that most people are aware of: a tankless water heater eliminates the possibility of running out of hot water, as is the case with a storage tank system.

Is This Really True? Will I Never Run out of Hot Water?

″Do tankless water heaters run out of hot water?″ is a question we are frequently asked.To answer this, it is necessary to provide some background information on how a tankless system differs from a storage tank system.Exactly what it sounds like, a storage tank system does is store water that has been kept at a high temperature so that it is ready to be used.It does, however, imply that the tank’s supply of heated water may be exhausted, and it may take some time for the natural gas burners or electric heating components to restore the heated water supply supply.People may have to take cold showers until this is accomplished.Because there is no source of hot water that may be drained, a tankless system is the most energy efficient option.

As opposed to this, the water heater warms water only when there is a demand for it.In the event that you switch on the shower for hot water, the tankless system will detect the passage of water in the hot water lines and begin transferring heat to the water through a heat exchanger in the shower head.As long as there is demand, it will continue to operate in this manner – which means you will never run out of hot water!However, there is a disadvantage to doing so.

  1. Despite the fact that a tankless system cannot run out of hot water, it might be overwhelmed by the amount of demand.
  2. This cannot be accomplished with a single tap: you can run that one shower as long as you like and still have hot water.
  3. (However, please refrain from doing so!

Conserve water, conserve energy!) If more than one tap is supplying hot water on demand at the same time, such as multiple showers or a washing machine in use, the water heater will struggle to keep up and will consume more energy.In order to avoid this, we recommend that you consult with a competent water heater installer before making the decision to go tankless.It’s possible that your water use pattern may be better served by a storage tank system.Alternatively, you may desire to explore installing more than one tankless system (because they are modular, this is a straightforward process).

You may be confident that we will discover the most appropriate solution to satisfy the hot water needs of your household.

How Do You Determine the Size of the Rinnai Heater You Need?

  • Calculator
  • Tape measure

Rinnai heaters are manufactured by the Rinnai Corporation in Japan and are available in a number of sizes to accommodate a wide range of heating requirements.For the United States market, Rinnai manufactures heaters that work on either electricity or natural gas.Their heating capacity is measured in British Thermal Units (BTUs), which is the industry standard unit of measure for heat output in residential heating equipment.With a Rinnai heater, the amount of heat it can produce dictates the size of room it can successfully heat.

The area of the rooms you need to heat may be calculated as follows: multiply each room’s length by its width in feet, then add the results together.

Consult a heating guide, such as the one given in the resources section, to determine the number of BTU per square foot that you require based on your local climate and the amount of BTU you have available.

In order to determine the total BTU rating you’ll want from your Rinnai heater, multiply the square footage by the BTU per square foot value. The BTU ratings on all Rinnai heaters are specified, ranging from 8,000 to 40,000 or more, providing you with a great deal of choice in the type you choose to purchase.

Big tubs need big water heaters

Instructions from Ed the Plumber on how to acquire enough hot water to fill a whirlpool tub.Q: Due to the fact that we only have a 40-gallon water heater, we seldom ever use our 6-foot whirlpool tub in the bathroom, which takes more than an hour to fill.We fill it halfway, then wait around 40 minutes for the tank to warm before finishing the filling.So, as you might understand, by that time the initial batch of water has begun to chill a little and we never get a really hot bath.And we squander all of our time!Due to the fact that there are only two of us that live here, I do not want to upgrade to a larger water heater because it seems like a waste to keep all of that hot water.

I’m considering installing a tankless water heater, but the expense of doing so is very expensive.I want to be sure that a tankless water heater will function correctly on such a huge tub before I make such a hefty investment.Is there anything else you’d want to suggest?— Fred, Georgia A: Every week, I am astounded by the amount of queries I receive about whirlpools that have inadequate water heaters installed!

  1. Someone is not carrying out his responsibilities.
  2. The problem is that either there are some unlicensed plumbers out there who do not understand or clearly explain to customers that larger tubs require larger water heaters, or homeowners are refusing to upgrade their water heaters in order to save money on installation costs, preferring instead to stick with an undersized water heater.
  3. Please allow me to make things absolutely clear so that we can move on from this situation.

Whenever possible, consult with a licensed plumber who will obtain the necessary permissions and calculate the appropriate size of the water heater that will be required for your whirlpool tub installation.If your current water heater is not large for the task, you will need to update to a larger water heating system.This isn’t rocket science, after all.If you’re going to conduct this task, please make sure it’s done correctly and in accordance with local codes.

See also:  How To Get The Right Size Tankless Water Heater?

Sorry for veering off topic, but it appears that individuals are now more concerned with having a whirlpool than they are with it working well.I apologize for any inconvenience.Now, let’s get back to your question concerning replacing your current water heating system.

You will need to deal with a certified plumber, who should be able to provide you with three different options.First and foremost, if you choose a tankless water heater, your existing water heater will be removed and the new tankless water heater will be put in its stead.Please keep in mind that tankless water heaters are available in a variety of sizes, and you should choose one that will provide a strong flow to the tub.Filling a large tub with water from a tiny tankless water heater might take a long time.

Second, just go ahead and replace your current water heater with a larger water heater that is more powerful.Third, if a bigger water heater cannot be installed because of space constraints and a correctly sized tankless water heater is too expensive, you can install a second regular water heater next to your existing tank.Two smaller water heaters can perform the same function as one larger water heater.

  1. Inquire with your plumber about the expenses of all three alternatives before making a decision on the overall installation and yearly running costs.
  2. Whatever you decide, at the very least you’ll be able to relax in a lovely, hot whirlpool tub now that you’ve gotten your act together.
  3. The author of ″Ed Del Grande’s House Call″ and the host of television series on Scripps Networks and HGTVPro.com, Master Contractor/Plumber Ed Del Grande is well-known in the construction and plumbing industries.

In order to obtain more information, please visit eddelgrande.com or send an email to eddelgrande@hgtvpro.com.Always check with your local contractors and building codes.

How to Determine the Required Size of a Tankless Hot Water Heater

Tankless water heaters are available in two different configurations: gas and electric.The majority of the time, gas-fired water heaters are more efficient and heat the water more quickly than electric-powered models.They must, however, be vented, and the initial cost of installation and piping is significantly greater.Electric tankless heaters are less complicated to install, but they are incapable of heating huge volumes of water at a temperature that is suitable for use.A fundamental size criterion for deciding between them is that a tankless electric heater may be sufficient for one or two persons depending on their needs.When there are more than two persons in the house, a gas-fired tankless heater is the best option.

Determine the Mounting Space

Water heaters without a tank are available in two different configurations: gas and electric.A gas-fired water heater is often more energy efficient and heats water faster than an electric-powered device.Although they are more energy efficient, they are more expensive to install and maintain since they must be vented.Water heaters that use electricity are more convenient to install, but they are incapable of heating vast volumes of water sufficiently to be useful.It is important to note that a tankless electric heater may be sufficient for a single or two persons, depending on their size.Using a gas-fueled tankless heater is the best option if you have more than two individuals.

Measure your Cold Water Temperature

Using a thermometer, determine the temperature of your cold water.The first step is to determine the temperature of your water.Your tankless unit will heat this water to the temperature you specify, and it should be capable of sustaining that temperature at the maximum flow rate you specify.For example, 110 degrees Fahrenheit is widely considered to be the optimal temperature for kitchen sink hot water.Assuming a cold water flow of 50 degrees Fahrenheit, the tankless water heater must be able to raise the incoming water temperature by 60 degrees Fahrenheit while operating at maximum flow rate in order to maintain the kitchen water flowing at 110 degrees Fahrenheit.

Determine your Water Flow Rates

The efficiency of a tankless water heater is influenced by the amount of water that flows through your property.A low-flow shower head may utilize up to 1.5 gallons of hot water per minute, which is referred to as GPM in the industry.While doing dishes, a sink may consume 1.5 GPM of water from the faucet, but a running bathtub may use 4 GPM.The majority of appliances are rated in GPM.For example, the GPM rate of a dishwasher will be printed on the energy guidance tag or the manufacturer’s model number tag attached to the device itself.To ascertain the basic GPM measurement, such as the flow rate of a bathroom faucet, you may set a gallon jug beneath the faucet and wait how long it takes for the jug to fill up.

The fact that one jug can be filled in 20 seconds indicates that three jugs can be filled in one minute, or that three times one equals three for your GPM rate.

GPM Heating Basics

When 5 GPM of water is consumed, the temperature of most gas-fired tankless heaters rises by 70 degrees Fahrenheit or more. When a maximum of 1.5 to 2 GPM of water is consumed by most electric tankless systems, the temperature rises by around 70 degrees. The lower the amount of water that is being utilized at any particular time, the higher the temperature of the water that may be achieved.

Determine your Tankless Water Heater Size

Start with the temperature of the entering water, which in this case is 50 degrees Fahrenheit.Calculate the maximum flow rate of gallons that may be achieved during usage.For example, one person is taking a shower with a flow rate of 1.5 GPM and a target temperature of 105 degrees Fahrenheit.The dishes are being done by one person at a rate of 1.5 GPM and at the ideal temperature of 110 F.The washer is likewise operating at a rate of 2 GPM, with an average washing temperature of 120 degrees Fahrenheit.There are a total of 5 GPM within that time span.

In order to maintain the water temperature required for all of these activities at the same time, you should look for a tankless water heater that is capable of raising the temperature of the water to 70 degrees Fahrenheit at a rate of 5 gallons per minute (GPM) or higher.The majority of gas-fired water heaters are capable of performing this function.They are, on the other hand, rated for a specified temperature rise over a specific number of GPM.For example, a 200,000 BTU gas-fired tankless unit is capable of raising the overall water temperature by 50 degrees Fahrenheit while delivering a maximum flow rate of 7.4 GPM.

  1. As a general rule of thumb, for every GPM that is deducted from the total, a 10-degree rise in water temperature is permitted.
  2. Using this scenario, a 200,000 BTU water heater would be able to heat all of the running water in a house to 110 degrees Fahrenheit when the flow rate is 6.4 GPM, and it would be able to heat all of the flowing water to 120 degrees Fahrenheit when the flow rate is 5.4 GPM.
  3. Because just the washer requires this temperature, a tankless water heater with a capacity of 200,000 BTUs is deemed excessive in this example.

Consider the Ground Water Temperature

In the very northern portions of the nation, the water temperature can drop to as low as 37 degrees Fahrenheit.The water temperature in the far southern parts can reach the upper 70s degrees Fahrenheit.During the summer months, water temperatures range from the high 50s to the low 60s in the Midwest.The greater the temperature of the incoming water, the less energy is required to heat it and the less temperature rise is required to meet your hot water requirements.As an example, an electric tankless heater certified to raise the water temperature by 55 degrees at 1.5 GPM will provide you with a 120-degree temperature if the incoming water temperature is 65 degrees or greater; otherwise, the heater will not work.

Choose What Size Water Heater You Need Like a Pro

  • When searching for a new water heater, one of the first considerations to make is the capacity of the water heater you want to purchase (i.e., the number of gallons the tank holds). According to conventional thinking, you should get the greatest heater feasible. However, it is more dependent on the number of people living in your home as well as the water heater’s capacity to recover from a power failure. Every household member should have 10-15 liters of hot water, according to industry standards. A 50-gallon water heater should be plenty for a household of four people, according to the manufacturer. Examine the capacity of the water heater, as well as the First Hour Rating (FHR) and your own particular Peak Hour Demand computation. The following is a basic estimate of the amount of water heater you will require: A 30-gallon water heater will enough for a family of two
  • a 30-40-gallon water heater will suffice for a family of three
  • and a 40-50-gallon water heater will suffice for a family of four.
  • A 50-60 gallon water heater will enough for a household of five
  • a 60-80 gallon water heater will suffice for a family of six or more.

These figures are simply estimates, and they might differ significantly depending on how much hot water you consume during your busiest hour.During a busy one-hour period, the Peak Hour Demand estimate determines how much hot water your household is expected to require.The First Hour Rating (FHR) of a water heater is the amount of hot water it can produce in one hour of operation.It would be beneficial if you additionally considered the fuel source and its physical dimensions.

Determining Tank Size Based on Family Size

  • Tank-style water heaters have a storage capacity of 30 to 80 gallons and are commonly used in residential settings. For the majority of households, 40-60 gallons is adequate. However, once again, this is dependent on your overall hot water usage. You must perform the arithmetic in order to determine the appropriate size for your home. To get you started, here’s a ballpark figure to get you thinking: In most cases, a 30-gallon water heater will be sufficient for households with one to two people.
  • Families of two or three people require a water heater that holds at least 40 gallons
  • a family of four people needs a water heater that holds at least 50 gallons. If you’re using electricity, 50 gallons will enough, and 40 gallons will suffice if you’re using natural gas or propane.
  • If your family has more than five members, an 80-gallon electric water heater or a 50-gallon gas water heater may be in your best interest.
  • Keep in mind that the list above is only a guideline, and as a result, you will not be able to draw any firm conclusions from it. The amount of hot water required varies from family to household. For example, a three-person household may discover that a 40-gallon water heater is insufficient to fulfill their demands, yet the same tank capacity may be sufficient for a five-person family. For example, some people take longer showers than others, and some families have a disproportionate number of appliances and fixtures that consume water from the hot water heater. As a result, it all comes down to how much water a family consumes on a daily basis. The following are some starting points for calculating your normal consumption: This includes both the quantity of persons taking showers and the time that they are taking them.
  • It is possible that heavy appliances will be utilized at the same time as people are showering.
  • The capacity of the primary appliances that were utilized to fill the tank
  • The frequency with which the bathtub is utilized. Is it better to fill the tub partly or completely?
  • Do you have any plans to renovate your bathroom or kitchen in the foreseeable future? If that’s the case, will you be upgrading to a larger bathtub?
  • Are you planning on having additional children or getting married in the near future, given that a water heater may last up to 15 years?
  • Consider putting one water heater for every two bathrooms in large residences, or one water heater per floor in multi-story buildings.

Evaluating the Peak Hour Demand and First Hour Rating

  • Now that you’ve performed the lifestyle audit described above and determined the Peak Hour Demand (PHD) and the First Hour Rating (FHR), you may go to the next step (FHR). This information will assist you in selecting a water heater that will meet your hot water requirements. What is the demand during peak hours? The quantity of hot water consumed during rush hour is referred to as the peak hour demand. In your house, it defines the time of day during which you consume the most hot water. Your busiest hour may be at 8 p.m., just before everyone goes to bed, or at 6 a.m., just before everyone rushes out the door to get ready for school or work. Simply said, it is the time of day when the greatest amount of hot water is drunk. What is the rating for the first hour? The First Hour Rating (FHR) of a water heater is the amount of hot water it can produce in one hour of operation. Take note that this is not the same thing as the maximum capacity for holding water in the tank. FHR is dependent on the fuel supply, tank size, and the size of the burner, among other factors. The FHR information may be found on the water heater’s Energy Guide Label, which is easily accessible. The checklist provided below might assist you in estimating your peak hour use. Always keep in mind that the peak-hour demand should be a bit lower than the first-hour rating of your heater. 4 gallons for hair shampooing per household member
  • 4 gallons for hand dishwashing
  • 4 gallons for face/hand washing per household member
  • 2 gallons for shaving
  • 10-15 gallons for showering per household member
  • 14 gallons for automatic dishwasher
  • 10-30 gallons for automatic washer (older clothes washers can use up to 45 gallons of water, whereas modern energy-efficient washers use as little as 5 gallons)

In the case of a household of five, the following is how you would calculate your peak hour demand.If you have three people showering every morning, two people washing their faces, and one person shaving and washing the dishes by hand, you will consume an average of 74 gallons of water every day.If your peak hour usage is 74 gallons, you should seek for a water heater with an FHR of 76-80 gallons, according to the chart below: Examples of a Sample Worksheet for Predicting Peak Hour Demand and First Hour Rating *Based on My Family’s Personal Experience* The information in the spreadsheet above is based on my family’s use.The amount of time your family spends during peak hours will most likely differ.

Sizing a Tankless Water Heater

  • It is less usual to find tankless water heaters than it is to find tank-style systems. Their popularity is progressively gaining ground, mostly due to the fact that they take up less space and lower energy expenses by 25 percent. If, on the other hand, you choose a tankless water heater, a whole other set of considerations come into play. It is not need to worry about the tank’s capacity because these devices do not have any water storage. You should, however, pay particular attention to the flow rate and tempera

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