What Size Tankless Water Heater To Replace A 75 Gallon?

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

  1. An expensive tankless water heater that is not powerful enough to meet our needs is one of the most common mistakes people make when purchasing a tankless water heater.
  2. Tankless heaters should not be purchased based on their size.
  3. Neither should they be purchased based on their size, since this will waste energy.
  4. The size of your tankless water heater should be as close to your household’s hot water requirements as feasible.
  5. In what size tankless water heater do I need to invest my money?
  6. 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.
  1. 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?
  1. 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.
  2. From 9 p.m.
  3. to 11 p.m., most families have the greatest demand for hot water.
  4. That is the time of day when we shower, brush our teeth under a hot faucet, and perhaps even have the dishwasher on.
  5. We need to keep track of how much hot water we’re using.
  6. 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
  1. 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.
  2. It is possible to get anything from 2 GPM to 12 GPM of hot water using a tankless heater.
  3. How many gallons per minute do you require?
  4. The ones with a flow rate of 5-10 GPM are the most suitable for the majority of houses.
  5. As previously stated, the cost of a tankless water heater grows in direct proportion to the capacity of the unit.
  6. It should be noted that electric tankless hot water heaters are suited for modest water demands up to 8 GPM.
  1. 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

  1. When comparing the specifications of different tankless heaters, you will see that they all list the maximum GPMs.
  2. When it comes down to it, the highest GMP that your tankless heater will truly reach might be far lower.
  3. What is the source of the discrepancy?
  4. 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.
  5. For example, in south Texas, the inflow water temperature is 77 degrees Fahrenheit.
  6. In Minnesota, for example, the temperature of the input water might be as low as 37 degrees Fahrenheit.
  1. That represents an additional 40 degrees Fahrenheit differential that a tankless water heater must overcome.
  2. Calculation in a few words: Consider the following scenario: we have a tankless heater with a maximum water flow of 10 GPM.
  3. Because the input temperature is 77 degrees Fahrenheit in Texas, we can really obtain 10 GPM of 110 degrees Fahrenheit water.
  4. The heater must heat water from 77 degrees Fahrenheit to 110 degrees Fahrenheit, a difference of 33 degrees Fahrenheit.
  5. In Minnesota, on the other hand, the inlet water temperature is 37 degrees Fahrenheit.
  6. 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.

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.

  1. 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.
  2. It’s important to consider the operating costs as well, especially with larger units.
  3. You can find out how much power larger electric tankless water heaters consume by visiting this page.
  4. 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?

  1. 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.
  2. Obviously, a tankless water heater designed for a family of three will be smaller than one designed for a family of five.
  3. But what are the specific GPM (for gas-powered engines) or kW (for electric-powered engines) figures?
  4. 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.
  5. A table containing estimations may be seen below.
  6. Unfortunately, the confidence ranges are extremely wide.
  1. 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

  1. 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.
  2. 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.
  3. As we’ve shown, the maximum GMP is a function of context.
  4. It is dependent on where you live in the United States (because that affects the inlet water temperature).
  5. Power, on the other hand (measured in kW), is absolute.
  6. 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.
  1. All things considered, you must also consider certain financial calculations, for example.
  2. It is advised that you check here to see if a tankless water heater is actually worth the investment (we did some calculations).
  3. Let’s take a look at two real-life situations.
  4. 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.
  5. Second, the number of people who live (and utilize) hot water in your home is taken into consideration.
  6. 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)

  1. If five individuals reside in the same house, they can use multiple faucets or showers at the same time.
  2. This must be taken into consideration while determining the appropriate size of a tankless water heater.
  3. Showers are the home hot water user that consumes the most hot water the fastest.
  4. 5 people can also run several hot water faucets at the same time, as well as a dishwasher and do laundry, among other things.
  5. 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.
  6. The tankless heater has to work extra hard to raise the water temperature to 110°F or 120°F, depending on the situation.
  1. 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.
  2. 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.
  3. Keep in mind that, especially with larger units, tankless water heater circulation pumps can save you a significant amount of money on hot water.
  4. These pumps come in handy when you need hot water from a faucet or shower in a short amount of time.
  5. You won’t have to wait for hot water to start flowing, wasting all of the cold water that would have been wasted in the meantime.

How Many Tankless Heaters Do I Need?

  1. This is a rather typical topic, especially when it comes to larger homes.
  2. Here’s how it works: In the majority of situations, one tankless heater is sufficient to heat an entire house.
  3. 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.
  4. It makes logical in these situations to install two tankless water heaters.
  5. 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.
  6. During times when we require a large volume of hot water, the electric tankless water heater is activated to provide assistance.
  1. 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.
  2. Specifically, the plumbing for each units is separate in this instance.
  3. I hope this has been of assistance.

What Size Tankless Water Heater Do I Need?

  • Tankless water heaters are automated household equipment that provide hot water to your household whenever you need it. They may be installed in any location in your home. Their ability to provide an instant and endless flow of hot water, lower electricity consumption, simple installation, lower maintenance costs, longer life expectancy, tax breaks, and longer warranties are just a few of the reasons why they are becoming increasingly popular in both residential and commercial construction. The most important reason is that these heaters are meant to save you more room because they can be mounted on a tiny piece of the wall, as opposed to the traditional tank-water heaters that take up a lot of floor area. The following criteria should be considered if you plan to install tankless models and are unclear of the size to purchase: The size of your home
  • the pace at which water flows through your home
  • the change in temperature
  • the number of people in your family

In this essay, we’ll go into further depth about each of these aspects. However, before we go any further into the subject, it is critical that you understand that you should never purchase a tankless water heater that is lower in capacity than you actually want simply because of price disparities. Before we get started, let’s have a look at a brief chart.

Sizing Guide for Residential Tankless Water heater

Household Occupants Usage Capacity Required (Measured in Gallon)
Electric Gas
 1-2 people Regular/ Low 30 30
High 40-50 40-50
 2-3 people Regular/Low 40 40
High 50 40-50
 3-4 people Regular/Low 50 40
High 80 50-75
5+ people Regular/Low 80 50
High 80+ 75

1. The Size of Your House

  1. Tankless water heaters are available in a variety of sizes.
  2. However, practically all contemporary water heaters are capable of completely steaming the whole water supply of your home.
  3. Inefficient versions may be obtained by purchasing smaller models, which are limited to heating the water that flows into specific bathrooms in your house.
  4. While traditional storage tank heaters can only store and heat the quantity of water that you anticipate using, tankless heaters can store and heat as much water as you are able to flow through them.
  5. When selecting a size, make sure it is not too little that it produces less warm water than is required to fill all of your bathrooms.
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2. The Rate of Water Flow in Your House

  • We’ve established that tankless water heaters are different from traditional tank heaters in that they steam the water as it enters your home, rather than heating it. This implies that the rate at which water is released from your faucets is governed by the flow rate supplied by your water heater, not the other way around. Taking this element into consideration allows you to operate more than one faucet or shower at the same time without your faucet slowing down. Given that the typical flow rate of one shower head is 1.8 gallons per minute, it is possible that another shower will begin to run alongside the first shower at a rate of almost the same as the first shower. If both showers are linked to the tankless water heaters, the tankless water heaters must be able to provide sufficient flow rates for both showers. Adding up the flow rates of the two showers will give you the flow rate that you will need for your tankless water heater. 1.8 GPM (shower 1) plus 1.8 GPM (shower 2) equals 3.6 GPM total flow (required tankless heater flow rate) During the time that those two showers are running, it is very unusual for additional hot water taps or faucets in the kitchen or another bathroom to be running simultaneously
  • this increases the needed flow rate by the total flow rate of the other hot water taps and faucets. We’ve included some average flow rates below to assist you in estimating the flow rates of the majority of your faucets. The actual flow rates for your home and its many appliances may differ from one another. Bathroom faucet flow rates range from 0.5 to 1.0 GPM
  • showerhead flow rates range from 1.5 to 2.0 GPM
  • kitchen tap flow rates range from 2.0 to 6.0 GPM
  • dishwasher flow rates range from 1.5 to 2.5 GPM
  • and laundry washer flow rates range from 2.5 to 3.5 GPM.

3. Temperature rise

  1. Following the calculation of the flow rate of each faucet in your home, you must decide how much heat your heater must create in order to provide you with the necessary heat in your water outlets.
  2. The needed temperature rise will be determined by taking into account the temperature of the water that enters your house and that of the water that you wish to have flow out of your tap when calculating the required temperature rise.
  3. We will suppose your home’s incoming water supply is 45°F and your shower (which is connected to your tankless heater) will deliver water at 105°F; the temperature raise necessary is 60°F.
  4. Heater temperature rise (60°F) is calculated as follows: expected shower temperature (105°F) minus incoming water temperature (45°F).
  5. To obtain the appropriate temperature in your shower, your heater must heat 1.8 gallons of water by 60 degrees Fahrenheit every minute, assuming that the shower flows at a rate of 1.8 GPM.
  6. It’s also worth noting that typical ground temperatures may fluctuate between various US states due to the fact that some states are generally warmer or colder than others on a national scale.
  1. Some states are expected to have temperatures as high as 75 degrees, while others will have temperatures as low as 35 degrees, according to estimates.
  2. Knowing the temperature of the groundwater in your state will assist you in determining how hard your heater will have to work.
  3. If you’re not sure what it is, you may use the assumption that the temperature is 40 degrees to make sure you don’t underestimate the amount of temperature rise that will be required.

4. Your Household Size

  • Having determined the flow rate of each faucet in your home, you must now calculate the amount of heat your heater must create in order to provide you with the necessary heat in your water outlets. When determining the needed temperature raise, we will take into account the temperature of the water that comes into your home as well as the temperature of the water that you wish to flow out of your tap. Consider the following scenario: the temperature of your home’s incoming water supply is 45°F, and your shower (which is connected to your tankless heater) is supposed to give water at 105°F
  • the needed temperature rise is 60°F
  • Heater temperature rise (60°F) is calculated as follows: expected shower temperature (105°F) minus incoming water temperature (45°F) To obtain the correct temperature in your shower, your heater must heat 1.8 gallons of water by 60 degrees Fahrenheit every minute at a flow rate of 1.8 gallons per minute. It’s also worth noting that typical ground temperatures may fluctuate between various US states due to the fact that some states are normally warmer or colder than others in the country. The temperature in certain states is expected to reach up to 75 degrees, while in others it may drop to as low as 35 degrees. Knowing the temperature of the groundwater in your state might assist you in determining how hard your heater will have to work. You can make an educated guess at a temperature of 40 degrees to guarantee that you don’t underestimate the amount of temperature rise that will be necessary.

We’re looking at an estimated flow rate of around 13.6 gallons per minute, which may be higher than the average rate of flow in our area. Tankless heaters are designed to provide smooth heating operation at peak periods as well as during periods of average consumption. When sizing your tankless heater, consider the highest potential simultaneous usage.

Gas Tankless Water heater or Electric Tankless Water Heater?

  1. Aside from the size, the other component that influences the operation of a tankless water heater is the size of the tankless water heater.
  2. Tankless water heaters can heat up to 5 gallons of water to 70 degrees Fahrenheit in one minute on average, however electric tankless water heaters can only heat 2 gallons of water to 70 degrees Fahrenheit in the same amount of time.
  3. We picked 70 degrees Fahrenheit since that is the temperature rise necessary for normal groundwater at 40 degrees Fahrenheit to reach a sweltering 110 degrees Fahrenheit.
  4. Tankless gas water heaters have a noticeable advantage over their electric equivalents in terms of power, albeit the amount of power varies depending on the brand and type.
  5. Before making a purchase, always double-check the product specs for GPM and temperature increase ratings.

Tankless Water Heater Size FAQs

You may still have some queries about the size of the tankless water heater you require; we will attempt to answer them in this section.

Which sizes last longer?

  1. Tankless water heater longevity is mostly determined by the type of tankless water heater used rather than its size.
  2. The lifespan of a gas tankless water heater is often greater than that of an electric tankless water heater.
  3. However, the type and brand of the product have an impact on the lifespan; however, in general, gas-fired tankless heaters have a lifespan of more than twenty years, whereas electric water heaters have a lifespan of seven to ten years.

Where can I find the right model size?

Departmental plumbing stores are likely to carry all of the available model sizes. For your convenience, you may want to try purchasing them online; however, make sure you carefully read the requirements to avoid any misunderstandings.

What size tankless water heater can I install myself?

Because you will require the skills of a skilled installation, this is not a do-it-yourself project. The installation procedure is time-consuming and difficult. It entails gas connections, electrical circuits, propane units, and other such things. In such instances, the business will always recommend a tech person to customers.

What size tankless water heater is easier to maintain?

  1. In comparison to bigger models, it seems obvious that smaller model sizes would be less difficult to keep up with.
  2. Regardless, you will want the services of a professional to do routine maintenance on your tankless water heater at regular intervals.
  3. This involves checking for leaks, inspecting the air vents, and cleaning the burner, among other things.
  4. If you reside in a hard water area, you should consider flushing your tankless water heater with vinegar every three weeks to prevent sediments from blocking the heat exchanger, which is especially important for small tankless water heaters.

What are the prices for different tankless water heater sizes?

  1. In comparison to bigger models, it seems obvious that smaller model sizes would be less difficult to maintain.
  2. Regardless, you will require the services of a professional to inspect and service your tankless water heater on a consistent basis.
  3. There are a variety of things to look for, such as leaks, air vents, and the burner itself.
  4. It is recommended that you flush your tankless water heater with vinegar every three weeks if you reside in a hard water area to prevent sediments from blocking the heat exchanger, which is especially important for small tankless water heaters.

Conclusion

Following the calculation of your water flow rate and needed temperature rise for typical hot water consumption, make sure to account for peak usage periods so that your heater can provide you with hot water at all times. You can let us know if there is anything further you need to know after reading over all of the information we’ve provided in the comments section below.

What Size Tankless Water Heater Do I Need? (With Calculator)

Once you’ve made the decision to acquire a tankless water heater, the following step is determining what size tankless water heater you’ll need for your household. This helpful tankless sizing calculator will assist you in determining the appropriate tankless size for your house. Simply answer the questions, and the program will calculate the results for you!

Tankless Sizing Calculator

Tankless Water Heater Sizing Calculator

Make use of our Sizing Calculator to figure out what size you need: The rate of flow and the temperature are increasing.

Where are you located?

What Size Tankless Do I Need for a Family of 5?

  1. We wish we could give you a simple answer, but you will need to spend some time working through the calculator to discover your specific requirements.
  2. It is important to consider where you reside, how many fixtures will be in use during your peak hour, and whether or not you will be doing laundry or other appliances when deciding the appropriate tankless size.
  3. However, it’s fair to suggest that you’ll need to invest in a bigger tankless water heater.
  4. In the majority of circumstances, a tankless heater with a flow rate of at least 7 GPM will be required.
  5. The tankless sizing calculator provided above will assist you in determining the appropriate size for your house or business.

What is a Tankless Water Heater?

  1. Due to the fact that they only heat water when there is a need, tankless water heaters are sometimes referred to as on-demand water heaters.
  2. When a hot water faucet is opened, the tankless appliance is activated when cold water begins to flow through the water heater, causing the tankless appliance to switch on.
  3. A heat exchanger heats the water to the desired temperature as it circulates through it.
  4. As the water becomes hotter, it enters your domestic plumbing system as it makes its way to the open hot water faucet.
  5. As soon as the hot water faucet is turned off, the tankless water heater turns off and does not turn on again until there is another demand for hot water.
  6. A tankless water heater, in contrast to a standard tank-style water heater, which is restricted by the size of its tank, may provide an unending supply of hot water.
  1. Interested in learning more about the differences between tankless water heaters and regular water heaters?
  2. Continue reading.
  3. Please Visit This Site

What Does it Mean to Size a Tankless Water Heater?

  • Sizing a tankless water heater is the phrase used in the industry to describe the process of estimating the quantity of hot water your family uses in order to acquire a tankless appliance that will fulfill your hot water requirements. It is necessary to understand the following factors in order to appropriately size a tankless water heater: Changes in temperature (which are affected by where you reside)
  • Use during the day’s busiest hour (the time of day when you’ll need the most hot water)
  • Demand (the number of hot water fittings that are utilised during peak hour)

The answers to these questions will be entered into our tankless water heater size calculator, which will calculate the GPM required for your household’s demands. Your new tankless water heater may be purchased using the GPM that you have obtained from the manufacturer.

Why is Where I Live Important?

  1. Simply simply, the location of your home is critical in determining the required temperature increase.
  2. The temperature of the ground changes depending on where you live, and the temperature of the ground impacts the temperature of the entering water.
  3. The temperature rise is one of the most important factors to consider when determining the right size of a tankless water heating system.
  4. Suppose the incoming water temperature is 50°F and your tankless water heater is set to heat the water to 110°F.
  5. The temperature rise will be 60°F.
  6. The ground temperature is significantly colder in the Northern Region than it is in the Southern Region if you reside there.
  1. Because of this, you’ll need to invest in a more powerful tankless water heater in order to provide the amount of hot water required by your home.
  2. Don’t be concerned, our tankless water heater calculation takes this into consideration as well.

What Does Peak Hour Mean?

  1. In order to provide adequate hot water to your home when the demand is the highest, tankless water heaters must be capable of doing so.
  2. It is common practice to use the phrase ″peak hour″ when sizing a tankless water heater to refer to the time of day when you will want the most hot water.
  3. In the majority of situations, the busiest time is in the morning.
  4. Take a look at your morning (or peak hour) routine to get an idea.
  5. Is anyone taking a shower?
  6. Wash you do your own laundry?
  1. Do you want to run the dishwasher?
  2. Do you use a hand sink?
  3. All of these tasks necessitate the use of hot water.
  4. As a result, if they all occur at the same time, your tankless water heater must be capable of providing adequate capacity to accommodate them all.
  5. A tankless water heater that is not properly sized (or that is underpowered) can supply lukewarm water, making your shower less than enjoyable.
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What is GPM?

  1. Tankless water heaters have a flow rate measured in gallons per minute (GPM), which is the unit of measurement used to determine the flow rate.
  2. The flow rate is defined as the number of gallons per minute (GPM) of hot water that the tankless water heater can heat in one minute.
  3. The higher the GPM, the greater the amount of hot water that the tankless can provide.
  4. A tankless water heater that has a flow rate of 8 GPM will be able to supply more hot water than one that has a flow rate of 5 GPM, to put it another way.
  5. Water flow rate (GPM) is established by the number of fixtures (showers, hand sinks, and so on) that your household will be utilizing during the peak hour of use, taking into consideration the temperature rise.
  6. However, it is vital to highlight that you only need to consider the number of fixtures that are in use at the same period during peak hours.
  1. If you have two showers but only use one during peak hour (or if they are not both in use at the same time), you will only use one in your calculations if you only take one shower during peak hour.

Should I Purchase a Gas or Electric Tankless Water Heater?

  1. Once you’ve made the decision to go with a tankless water heater, the next important question is what kind of power source you’ll use.
  2. Both gas and electric tankless water heaters have advantages and disadvantages, and you should do your homework before making a decision.
  3. Read our post, Gas versus Electric Tankless Water Heater: Which is the Best, for more information.
  4. This page analyzes and contrasts the two fuel sources in detail.
  5. Operational expenses, installation costs, maintenance needs, and other critical variables are all taken into account in this report.
  6. Tankless water heaters powered by natural gas have a greater GPM than electric tankless water heaters, are more expensive to acquire and install, and require more maintenance than electric tankless water heaters.
  1. When compared to a traditional tank-style water heater, an electric tankless water heater is easier to install, requires less maintenance, and has a lower initial cost.

Which Brand of Tankless Water Heater Should I Buy?

  • There are many high-quality tankless water heater brands available on the market today, but there are also a handful that are less than fantastic. In the end, the manufacturer you pick will be determined by the model that best matches your requirements. With a tankless water heater from Rinnai, Rheem, or Stiebel Eltron, it’s difficult to go wrong with your choice. EcoSmart offers a wide range of models that are both functional and affordable. Nortiz, Navien, and Bosch are among well-known and recognized names in the industry. In the right circumstances, a tankless water heater may provide hot water to your home for 20 years or more. It is therefore essential that you choose a reliable manufacturer when purchasing your water heater. Additionally, it will be simpler to locate a repair technician to operate on your equipment. See our page on Gas Tankless Water Heaters for more information. We provide our best recommendations as well as a comprehensive buying guide.
  • See our page on Electric Tankless Water Heaters for more information. A buying guide is also included, in addition to our best picks:

I need to replace a 75-gallon water heater. What are the options?

  1. With a hydronic boiler heating the home, an indirect-fired tank operating as a zone off the boiler increases duty cycle on the boiler (thereby improving its as-used efficiency) and offers quicker recovery than most standalone high-temperature heaters.
  2. In addition, because there is no center-tank heat exchanger flue convecting heat out of the tank 24 hours a day, 7 days a week, indirect HW heaters have far lower standby loss than freestanding tanks, and they have less gaps in the insulation.
  3. Tank HW heaters (almost) never need to be larger than the largest tub that will be used to store the water.
  4. If you have a high-volume soaker-tub, there may be a solid purpose for the 75-gallon tank, but otherwise, there isn’t a compelling justification for it.
  5. Since the boiler produces hot water at a sufficiently high rate that the temperature at the faucet does not drop below bathing temperature, you can normally downsize the tank to 30 gallons and still fill most tubs with indirect tanks on larger boilers (100,000 BTU/hr or more).
  6. (If this occurs, increase the storage temperature by another 10 degrees Fahrenheit.) When using recirculation systems, the heating efficiency of hot water can be dramatically reduced if the system is keeping the distribution pipes hot even when no hot water is being pulled from them.
  1. The form of control is important; demand-type controls are significantly more efficient.
  2. If the distribution plumbing under the house is not insulated but is accessible, it is well worth the effort to retrofit R4 (3/4 inch) insulation ″Closed cell foam pipe insulation should be applied to any and all surfaces that can be reached, including the ″return″ line.
  3. Because the water will be kept warm enough to be useable for prolonged durations between draws, the recirculation pump’s duty cycle needs will be reduced, and the total thermal loss of the system will be reduced, as well.
  4. Insulating the cold water feed to a hot water tank for the first 6-10 feet closest to the tank, as well as any temperature/pressure overflow pipework closest to the tank, helps to decrease standby loss as well as energy use.
  5. (When installing gas-fired heaters, make sure to provide adequate clearances between the flue or burner and the pipe insulation to ensure that the heater complies with fire rules.) The 3/8 inch ″Foam pipe insulation supplied at big box retailers is only around R2- better than nothing, but nowhere near the highest R value that is monetarily reasonable.
  6. (The IRC 2012 specifies that the bare minimum insulation for tempered water distribution is R3.) It’s possible that you’ll have to look for it online, but it’s out there.

When it comes to retrofit issues, the pre-split material is the easiest to deal with.

What Size Tankless Water Heater Do I Need: Formulas and Examples

  1. House Weather is made possible by donations from readers.
  2. We may receive a commission if you purchase something after clicking on one of our links.
  3. If you are one of the increasing number of individuals who have been asking themselves, ″What size tankless water heater do I need?″ then you have arrived to the correct website..
  4. These types are in high demand because they provide a reliable and consistent supply of hot water on demand for your home.
  5. As an added bonus, they require no maintenance as compared to a traditional water heater tank, and they may lower your power expenses by up to 34% by heating only the quantity of water that is really needed.
  6. Among the other advantages of tankless models are their small footprint, which saves space, and their lengthy lifespan, which is twice as long as that of their regular counterparts.
  1. Before you buy a tankless water heater, you should first determine the answer to the following questions: what size tankless water heater do I require?
  2. What is the temperature rise I want to achieve and what is the maximum flow rate I want to achieve?
  3. For my home, how much water will be required?
  4. Finally, you must take into consideration the power source that is accessible in order to select the most appropriate model.
  5. You will be able to answer such questions in greater depth after reading this article, which contains thorough information on the subject.

What is meant by size in this case?

  1. When selecting a tankless heater, the size is important since it is a representation of the heating capability.
  2. Neither a smaller model that would not sufficiently heat the quantity of water you use, nor a larger one that would cause your energy bill to rise unnecessarily are good choices.
  3. We’ve outlined below how to properly size a tankless water heater, as well as the aspects that should be considered.

What to consider before choosing the right size

To choose the right size that will meet your demand, you should consider the quantity of water required by your household and the number and types of appliances your prospective tankless unit will be supplying with hot water so you can calculate the maximum temperature rise it can achieve at a given flow rate. This is in contrast with traditional models whose size is mainly determined by the size of your family. Once you have listed all the hot water appliances that will be operating simultaneously, tally their flow rates Sizing a New Water Heater – Energy.gov Tankless or demand-type water heaters are rated by the maximum temperature rise possible at a given flow rate. Therefore, to size a demand water heater, you need to determine the flow rate and the temperature rise you’ll need for its application (whole house or a remote application, such as just a bathroom) in your home. to get your target flow rate. Flow rate is calculated by GPM which refers to gallons per minute. For instance, shower heads are mandated to have a maximum flow rate of 2.5 GPM. Check the manual of your hot water appliances for its flow rate or look up the model number online and then use a chart such as the one in the next section to estimate it. Gas models also tend to be more powerful than electric tankless water heaters. We have elaborated on the pros and cons of each type of power source and how to calculate temperature rise further in the article.

What appliances you want to run

The question is, how many tankless heaters do you need to give you with rapid hot water while not using up too much electricity in the process? That will be determined by the amount of water that is necessary to be provided to certain of these devices.

Appliance          Flow Rate (GPM)
Shower head 2.5
Bathroom Faucet 0.5 – 2.0
Washing machine 1.5 – 2.5
Kitchen Faucet 0.5 – 2.0
Bathtub Faucet 3.0 – 4.0
Dishwasher 1.0 – 2.0
According to the EPA Showerheads – EPA Did you know that standard showerheads use 2.5 gallons of water per minute (gpm)? Water-saving showerheads that earn the WaterSense label must demonstrate that they use no more than 2.0 gpm. The WaterSense label also ensures that these products provide a satisfactory shower that is equal to or better than conventional showerheads on the market. EPA worked with a variety of stakeholders—including consumers who tested various showerheads—to develop criteria for water coverage and spray intensity. All products bearing the WaterSense label—including water–efficient showerheads—must be independently certified to ensure they meet EPA water efficiency and performance criteria. showering is one of the leading ways we use water in the home, accounting for nearly 17 percent of residential indoor water use – for the average family, that adds up to nearly 40 gallons per day. That’s nearly 1.2 trillion gallons of water used in the United States annually just for showering, or enough to supply the water needs of New York and New Jersey for a year! The United States Environmental Protection Agency (EPA) reports that an average family uses up to 40 gallons daily to shower, translating to approximately 17 percent of residential water consumption. If you might be showering when the dishwasher and washing machine are running, then you will need a heater with at least 5 GPM which is the minimum size suitable for most households. 2.5 GPM (shower head) + 1.0 GPM (dishwasher) + 1.5 (washing machine) = 5 GPM (required tankless heater flow rate). That output would also be ideal for two showers running concurrently. On the other hand, a model with flow rate of 2 GPM will suffice if it only feeds one bathroom faucet and one kitchen faucet which add up to 1 GPM. Manufacturers will typically indicate the maximum GPM for their gas-powered tankless water heaters which ranges from 2 to 12 GPM. Instead of GPM, electric units use kW to indicate the maximum operating power. Shower heads are regulated by federal and state authorities. For example, the maximum GPM for shower heads in Washington and California is 1.8 GP whereas Colorado and New York City allow a maximum of 2.0 GPM. Federal regulations Reduce Hot Water Use for Energy Savings – Energy.gov Faucets and appliances can use a lot of hot water, which costs you money. Look for ways to heat your water more efficiently and use less. limit flow rate to 2.5 gallons per minute at a water pressure of 80 pounds per square inch (psi). There are also incentives provided by some communities to local residents when they install low-flow fixtures that save both water and energy.

Temperature rise

  1. The quantity of heat required to give hot water to your family at the desired temperature is referred to as temperature increase.
  2. It is obtained from the temperature differential between the water entering the heater and the hot water being delivered by a tankless water heater.
  3. It takes 72 degrees Fahrenheit to raise the temperature of water from 38 degrees Fahrenheit to 110 degrees Fahrenheit when it is connected to a waterless tank heater and your kitchen faucet demands hot water at 110 degrees Fahrenheit.
  4. Faucets often have temperatures ranging from 110° F to 120° F, depending on the manufacturer.
  5. The expected shower temperature (110°F) minus the incoming water temperature (38°F) equals the required heater temperature rise (72°F).
  6. Because a washing machine in this home has a flow rate of 1.5 GPM, you’ll need a heater that can heat 1.5 gallons of water by 72°F per minute to produce the necessary output.
  1. Because temperatures vary from one region to the next, the temperatures of their groundwater likewise varies from place to place.
  2. While the average groundwater temperature in the United States is 57 degrees Fahrenheit, groundwater in Chicago is 47 degrees Fahrenheit, while groundwater in South Florida may reach up to 70 degrees Fahrenheit.
  3. Consider these factors, together with seasonal variations, while calculating temperature rise to identify the most appropriate heater for your location.
  4. Groundwater temperature can be measured using a thermometer or by using one of the several ground temperature map versions available online.
  5. Even if you are unable to obtain an accurate reading of the temperature of your groundwater, some users advise adopting a lower number of 40 to 50 degrees Fahrenheit in order to err on the side of safety.
  6. Tankless water heaters are more efficient when the temperature rise is less than 20 degrees Celsius.
See also:  What Size Hot Water Heater For 4 Bedroom House?

The size of your household

How many people live in your house? When and how often do they use hot water? This is one way you can find out how to size a tankless water heater with adequate output. If there are several people or appliances that will be using hot water at the same time, then you need a large size that can effectively meet that demand. Check out this table Reduce Hot Water Use for Energy Savings – Energy.gov Average Hot Water Usage by the United States Department of Energy on various appliances and their average consumption of hot water.
Activity   Gallons per use
Clothes Washer 25
Shower 10
Dishwasher 6
Kitchen faucet flow 2 per minute
Bathroom faucet flow 2 per minute
Total daily average   64
  1. It may be used to compute the maximum simultaneous use feasible in your home, which can then be used to determine how many tankless heaters you require.
  2. Whether your unit will be giving hot water to the entire house or only at the point of use will also influence the size of your unit?
  3. It goes without saying that a whole-house heater will need to be more powerful.
  4. However, you may choose to install tiny or medium-sized heaters for the shower, a kitchen faucet, or merely the washing machine, as an alternative.

Power source

  1. Tankless water heaters can be fueled by electricity or natural gas.
  2. The heating capacity of gas heaters is often double that of electric heaters, and they are twice as long-lasting as electric heaters.
  3. In order to provide hot water to whole households, natural gas is the preferable fuel source.
  4. Moreover, it is more suitable for low-temperature groundwater, which requires a strong heater to raise its temperature before it can be delivered as hot water at outlet points.
  5. Electric water heaters, on the other hand, are better suited for situations where there are few hot water appliances, warm incoming water, modest GPM needs, and point-of-use applications that do not necessitate a device with a high output.
  6. Take into account the cost and availability of the power supply.
  1. Gas goods are pricey, but they may wind up being cheaper or more expensive in the long term, depending on where you live and how much you use.
  2. Gas models are strong and long-lasting, but they need the installation of venting, piping, and gas, which increases the initial cost.
  3. Electric heaters are less expensive and less difficult to install.
  4. They are, however, prone to power failures, and only a few entry-level versions can match the huge volume of hot water produced by gas-powered water heaters.
  5. In addition, they have a shorter lifespan of 7 to 10 years as compared to gas-powered heaters, which may endure for a minimum of 20 years before needing to be replaced.
  6. In the end, your heating requirements and preferences will play a role in your selection.

Examples

We will now present two alternative situations in order to further demonstrate the aspects that must be considered when determining how many tankless heaters you require for your environment.

What size tankless water heater does a family of four need?

  1. Calculate how many hot water devices may be in use at the same time in order to determine the appropriate tankless water heater size for a household of four members.
  2. Then add up the GPMs of each device, and you’ll get the total GPM needed to meet the requirements.
  3. Consider the following scenario: it is a typical day at home with everyone.
  4. For example, let us suppose there are two showers, one for the parents and another for the children.
  5. It is computed as follows: If one parent and one child are bathing in separate rooms, and the other parent is in the kitchen preparing breakfast while the dishwasher is running, the total GPM is calculated as follows: A total of 2.5 x 2 GPM (2 shower heads) plus 2.0 GPM (kitchen faucet) plus 1.5 GPM (dishwasher) equals 8.5 GPM total (required tankless heater flow rate).
  6. After determining the needed GPM for the heater, we must determine the required temperature rise for the heater.
  1. If they dwell in Alaska’s frigid climate, the corresponding ground water temperature will be 35 degrees Fahrenheit.
  2. If the temperature of the faucet is 110° F, the equation is 110° F (desired temperature) – 35° F (temperature of Alaska groundwater) = 75° F.
  3. (required heater temperature rise).
  4. This means that the best tankless water heater for this household will need to have the capability of heating 8.5 GPM of water at 75° F per minute in order to satisfy the demand.

The perfect size for a couple that lives on north

Alaska has the coldest winters Where Are The Coldest Low Temperatures In Summer: Alaska Or The Lower 48? – Forbes Alaska is cold, very cold. By almost any measure of coldness, Alaska far surpasses any portion of the Lower 48 states (Contiguous U.S.). Alaska has the coldest winters, the coldest summers, the longest winter, the most freezing degree days, and on and on. Temperatures in the -30°s and -40°s are a near daily occurrence from November through March in the interior portion of the state. There is a very simple reason for this. Alaska is much farther north than the Lower 48 and receives much less solar energy. and summers in North America, so we can use the example above to calculate how to size a tankless water heater for a couple living in the northern region. One shower for the couple, a dishwasher, kitchen and bathroom faucet translate to the following GPM and temperature rise: 2.5 GPM (shower head) + 1.5 GPM (dishwasher) + 2.0 GPM (kitchen faucet) + 2.0 GPM (bathroom faucet) = 8 GPM (required heater flow rate). We will use the same equation we used in the previous section to calculate the required heater temperature since our examples are based in the same area, which gives us temperature rise of 75° F. The right size for this couple is a unit that can overcome 75° F temperature difference to heat 8 gallons of water per minute.

What to replace a 50-gallon water tank with?

  1. Water accounts for a significant percentage of a household’s costs, so if you’re looking to replace your 50-gallon water tank with a more energy-efficient one and you’re thinking, ″How many tankless heaters do I need?″ we’re here to assist you with your decision.
  2. First and foremost, keep in mind that tankless devices heat water on demand, as opposed to tanks that store hot water in tanks.
  3. Second, the climate of the location in which you reside will have an impact on the temperature of the groundwater or inflow water, which will in turn have an impact on the temperature of your heater.
  4. In order to cope with the low-temperature incoming water, colder climates necessitate the use of a unit with a high capacity.
  5. If you live in a cold climate, the Takagi T-H3-DV-N gas-powered water heater might be an excellent alternative.
  6. It has several functions and is capable of raising the temperature to the level necessary to supply hot water to four bathrooms.
  1. A 27-kW efficient electric heater with a temperature range of 80°F to 140°F and production of between 2.7 and 6.5 gallons of hot water per minute is an excellent choice for those who prefer an energy-saving option.
  2. In addition, you will save 50% on your energy bills.
  3. It is possible to replace a 50-gallon tank with one of the two alternatives above.

Final thoughts

  1. We’ve addressed the issue of ″how many tankless heaters do I need″ for families of various sizes so that you can match the size of your family to a model that is specifically designed to suit your water demands.
  2. In addition, we have listed all of the elements that will assist you in sizing your optimal tankless water heater, as well as our suggestions for both electric and gas-powered tankless water heaters.

References

  1. 1.
  2. Calculating the Size of a New Water Heater – Energy.gov When rating tankless or demand-type water heaters, the greatest temperature rise that may be achieved at a given flow rate is taken into consideration.
  3. 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).
  4. Showerheads – according to the Environmental Protection Agency Was it ever brought to your attention that a conventional showerhead uses 2.5 gallons of water per minute (gpm)?
  5. Showerheads that acquire the WaterSense designation must demonstrate that they utilize no more than 2.0 gallons per minute (gpm) of water.
  6. Aside from that, the WaterSense label assures that these devices deliver a suitable shower experience that is on par with or better than that provided by conventional showerheads on the market.
  1. The Environmental Protection Agency collaborated with a wide range of stakeholders, including customers who evaluated a variety of showerheads, to set standards for water coverage and spray strength.
  2. All goods that receive the WaterSense label, including water-efficient showerheads, must be independently certified to guarantee that they fulfill the Environmental Protection Agency’s water efficiency and performance standards.
  3. Reduce the amount of hot water you use to save energy – Energy.gov Faucets and appliances can consume a significant amount of hot water, resulting in a financial burden.
  4. Look for ways to heat your water more effectively and with reduced energy use.
  5. Reducing the use of hot water can result in significant energy savings.
  6. Usage of hot water on a regular basis In the summer, where are the coldest low temperatures to be found: Alaska or the Lower 48?

Alaska is really frigid, in fact, it is extremely cold.Alaska outperforms nearly every other state in the Lower 48 when it comes to freezing temperatures on practically any scale (Contiguous U.S.).Alaska has the coldest winters, the coldest summers, the longest winter, the most freezing degree days, and the list goes on and on.Alaska also has the most extreme weather conditions.

The core of the state experiences temperatures in the -30°s and -40°s almost on a daily basis from November to March.There is a pretty straightforward explanation for this.Alaska is located far further north than the Lower 48 states and so receives significantly less sun radiation.

What Size Tankless Water Heater Do You Need? (Calculate GPM Needed)

  1. When it comes to tankless water heaters, you’re not alone in feeling overwhelmed by the variety of alternatives available.
  2. For many homeowners, the question ″What size tankless water heater do I need?″ is a source of frustration.
  3. Our guide will assist you in determining the appropriate size tankless water heater for your needs.
  4. Here, we’ll guide you through the exact calculations in a step-by-step fashion so that you can choose a tankless water heater that provides the necessary quantity of hot water to your house while also ensuring that you never run out of hot water.

How to Size a Tankless Water Heater

  1. The first consideration in selecting a tankless water heater is determining the size of your existing hot water heater.
  2. Unlike typical tank water heaters, which are sized according to the number of people in the household, tankless water heaters are sized according to the number and types of fixtures or appliances they will service.
  3. The resulting value is referred to as ″GPM″ (Gallons Per Minute), or ″flow rate″ in certain cases, and it is used to estimate the size of your hot water heater.
  4. Walk through the process of calculating and selecting the appropriate size tankless water heater.

Step 1: Calculate How Many GPM for Your Tankless Water Heater

  1. If you sum up the flow rates of each individual fixture that utilizes hot water in your home, you may establish your own maximum GPM.
  2. This is just a method of determining how many gallons of hot water may be passed through the fixture in one minute by monitoring the flow rate.
  3. It is possible to determine the real flow rates for your individual fixtures by consulting your owner’s handbook or looking for the model number on the internet.
  4. Individual hot water appliance GPM rates that are running at the same time equals total GPM required.
  5. If you don’t have the original paperwork or a model number, you can substitute a generic GPM number for the sort of fixture you’re working with instead.
  6. Make use of GPM estimation charts to find this information, which may be found with a short internet search.
  1. In fact, you can search for something like ″How large of a tankless hot water heater do I need?″ and the results (such as this one) will almost always contain one of these simple to use charts.
  2. The sample chart below will assist you in determining the appropriate size tankless water heater for your home.
  3. Write down each GPM amount, whether it is the exact GPM of your fixture or an estimate, and then add them all together.
  4. Take into consideration any fixtures that would be running at the same time, but only if they would be using hot water.
Appliance Flow Rate (GPM)
Bathroom Faucet 0.5 GPM
Kitchen Faucet 0.5 GPM
Shower 2.5 GPM
Dishwasher 1.0 GPM
Clothes Washer 1.5 GPM

(Source)Keep in mind that if you don’t want to run out of hot water, you should overestimate the number of fixtures that might be running simultaneously!

Step 2: Determine Temperature Rise Needed

  1. It is necessary to consider not just the volume of water that has to be moved, but also how much of that water needs to be heated.
  2. Another calculation is the temperature rise, which is the length of time it takes to raise the temperature of groundwater to the desirable ″hot″ temperature you want it to be.
  3. Typically, this temperature is approximately 120 degrees Fahrenheit, although this is simply a personal preference.
  4. Using a ground temperature map, you may quickly determine the typical groundwater temperature in your local area.
  5. There are a number of different variants, some of which show temperature ranges for broader regions, while others provide more detailed temperatures for smaller ones.
  6. The map you choose to use when sizing a tankless hot water heater is entirely up to your personal taste and needs.
  1. The temperature rise will be calculated using whichever method you pick, by subtracting the groundwater temperature from your target hot water temperature.
  2. This is another another specification that will be used to determine the size of the water heater you require.
  3. The required temperature rise is equal to the difference between the desired water temperature and the incoming groundwater temperature (Image Source)

Step 3: Determine Your Power Source

  1. Choosing a power source for your tankless water heater is the next step to take into account.
  2. There is no simp

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