Read This Before You Buy a Tankless Water Heater
Consider the following: The method used by the majority of houses in this nation to heat water is ridiculously inefficient. Every year, we fill up large storage tanks of 40- to 50-gallon capacity with water and then continuously pump energy into them to ensure that we have hot water available anytime we want it. But, unfortunately, this is not always the case. The wait for the tank to reheat might be lengthy if a teenager is taking a long shower or the spouse is enjoying a long soak in the tub.
Is there a chance of a leak?
Tankless Water Heater Installation: Is It Worth It?
Investing in a tankless water heater has a number of benefits, as detailed above. It creates hot water just when you use it and for as long as you require it, resulting in a reduction of 27 to 50% in fuel expenses when compared to tank-type heaters. (A typical gas-fired tank wastes 40 to 50% of the fuel it burns, according to the manufacturer.) As a result, there is virtually little danger of a catastrophic leak occurring because there is no tank to collapse. Furthermore, since their introduction in the United States in the 1990s, tankless heaters have become increasingly sophisticated, with features such as built-in recirculating pumps (which provide “instant” hot water) and wireless connectivity, which alerts you via smartphone when a unit requires servicing.
Our tankless water heater guide will explain how they function, what you should know before purchasing one (and before the installation comes), and the idiosyncrasies of how they operate so that you won’t be caught off guard if you decide to go tankless.
How Does a Tankless Water Heater Work?
A tankless water heater has several advantages, and these are the arguments in favor of purchasing one. The heater only provides hot water when you need it and just for the amount of time you need it, saving you 27 to 50% on fuel expenditures as compared to tank-type heaters. (A typical gas-fired tank loses 40 to 50% of the fuel it burns, according to industry standards.) Furthermore, because there is no tank to fail, there is essentially little likelihood of a catastrophic leak occurring in this configuration.
Our tankless water heater buying guide is provided below.
Download the guide today.
- It all starts with the first turn of the hot-water faucet (1). A flow sensor (2) detects the presence of water entering the heater and sends a signal to the control panel, causing the heater to begin generating hot water. During operation of a natural-gas-fueled unit, thecontrol panel (3) activates thefan (4), which pulls in outside air, opens the gas valve (5), which allows the gas to flow into the unit, and ignites the burner (6). In order to transmit heat from the flames to water passing through the exchanger’s tubing, a heat exchanger (number 7) is used. The mixing valve (8) regulates the temperature of the superheated water that exits the exchanger. Whenever the temperature sensor (9) detects water temperatures that are too high or too low for the intended setting, the panel will modify the gas valve, the mixing valve, and the flow-regulating water valve (10) in accordance with the results. Ventilation is provided by a sealedvent (11) (or a couple of vents) via a roof or exterior wall, which removes exhaust gases and supplies combustion air to the burner.
Several people were thanked for their contributions: Phillip Maxwell, Residential Product Manager, Rheem; Eric Manzano, Product Training Supervisor, Noritz; Joe Holliday, Senior Vice President, Product and Business Development, Rinnai; and Fred Molina, Water Heater Products Manager, Bosch Thermotechnology
What to Know About Tankless Water Heaters
Thanks to Noritz for the use of his photo.
How Much Does a Tankless Water Heater Cost?
Prices range from approximately $170 for modest gas-fired units to more than $2,000 for high-output heaters that can serve two showers at the same time; $1,000 is a reasonable starting point for most buyers. Electric heaters without a tank range in price from $90 to $900. The expenses of a first-time installation are higher than the price of a simple tank replacement. Electric tankless water heater installation (see item below headed “Installing an Electric Tankless Water Heater”).
How to Install a Tankless Water Heater
This is a work that should be left to the professionals, since it entails creating leak-free water, vent, and gas connections in the case of gas or propane units, or upgrading the wiring and circuit-breaker panel in the case of electric units, and it is best left to the professionals.
Tankless Water Heater Maintenance
Sign up to have a professional do an annual service that includes cleaning or replacing water and air filters, as well as inspecting the burner’s operation. The use of a vinegar flush every 500 hours in places with hard water prevents mineral accumulation, known as scale, from blocking the heat exchanger. That 20-minute task may be completed by a professional or by a homeowner.
How Long Do Tankless Water Heaters Last?
It is expected that gas-burning tankless water heaters would last 20 years or longer, which is two to three times longer than tank-type heaters. Tankless electric units have shorter life lifetimes, ranging from 7 to 10 years, compared to conventional units.
Where Can I Buy One?
They may be found at plumbing supply stores, big-box stores, and internet sellers, among other places. Alternatively, you may order one via your plumber.
Pros and Cons of Tankless Water Heaters
Thanks to Noritz for the use of his photo.
PRO: They’re Compact
As a result of new federal requirements requiring stronger insulation to decrease standby heat loss, the size of newer tank-type water heaters has increased. Consequently, they may not be able to fit into locations where an older heater with the same capacity might. Tankless gas heaters are approximately the size of a suitcase and are mounted on the wall.
PRO: They’re Safer
As a result of new federal requirements requiring stronger insulation to decrease standby heat loss, the size of newer tank-type water heaters has increased in recent years. As a result, they may not be able to fit into locations where an older heater with the same capacity might. They are roughly the size of a suitcase and are mounted to the wall with a screwdriver.
PRO: They’re Easy to Winterize
Owners of vacation homes are well aware of how long it takes to drain a water-heating tank prior to closing up a house for the season. An electric compressor may drain a tankless heater in a matter of seconds, after which it can simply be unplugged.
CON: They’re Sensitive to Slow Flow
These devices automatically shut off if there is too much scale accumulation in the pipes, or if the aerators in the faucets and showerheads get blocked, or if a turned-down faucet limits water flow to around 0.3 gpm.
CON: The Payback Takes Awhile
An annual savings of only around $100 for a household using a $1,000 tankless gas heater vs a $400 tank-type heater is possible, depending on how efficient the heater is and how much hot water is utilized.
The savings, however, begin to accrue after six years, when many tanks are reaching the end of their useful lives due to the extended lifespan of tankless gas systems.
New Tankless Water Heater Technology
Thanks to Noritz for the use of his photo. The advancement of tankless technology is ongoing. Here are a few of the most recent enhancements:
Higher Efficiency
Condensing gas heaters can extract up to 96 percent of the heat from a fuel, which is a 17 percent improvement over first-generation tankless devices. This is possible because of a second heat exchanger, which collects a large portion of the exhaust heat before it exits the vent. In addition to being around 25% more expensive than noncondensing heaters, condensing heaters produce acidic condensate that must be neutralized. If a heater doesn’t come with a built-in neutralizing cartridge, the installation will have to install one after the fact.
Instant Hot Water
Despite the fact that tankless water heaters heat water in around 15 seconds, you must still wait for the hot water to reach your shower head or faucet, just as you would with a tank-type heater. The recirculation pump should be used when the distance between the heater and the fixture is greater than 50 feet. This will conserve water and minimize the amount of time spent waiting. It is this pump that pushes the cold water in the pipes back through the heater. The pump can be activated by a timer, a push button, a motion sensor, a smart speaker, or a smartphone (see illustration above).
Wi-Fi Compatible
Tankless systems with digital connectivity let you to control the temperature as well as monitor gas and hot-water use from your mobile device. Furthermore, the device is capable of identifying the cause of a problem. Please communicate this information to your plumber so that he or she may arrive on the job site knowing exactly what has to be done. This function also eliminates the need for any guessing when it comes to determining when it is time to descale.
Tankless Water Heater Rebates: A Great Way to Save
Carl Tremblay captured this image.
What Size Tankless Water Heater Do I Need?
Here’s how the specialists ensure that your water heater produces adequate hot water: 1. A large burst of BTUs is required for a tankless heater to convert cold water into hot water in a matter of seconds. However, if a heater’s Btu output is insufficient to meet demand, it will reduce the flow rate or, in the worst scenario, offer tepid water. A plumber considers three aspects when determining whether or not a heater will be able to satisfy the demands of a household:
- The temperature of the water that enters the heater
- The maximum demand for hot water expressed in gallons per minute (gpm)
- The efficiency of the heater, as shown by its Uniform Energy Factor, which may be found in the product specifications
- The first step is as follows: A professional determines how many Btus per gallon of water heater is required to increase the incoming water temperature to 120 degrees (see the map on the next slide)
- Flow rates for all of the appliances and fixtures that may be consuming hot water at the same time are added together to form peak demand, which is calculated as follows: (These rates are detailed in the next slide.) As a result of not bathing or washing in 120-degree water, we save around 20% on our overall use. Water-saving fixtures and appliances, as well as delaying laundry while the shower is in use, can help you minimize peak consumption. In the calculation, the total Btu production is computed by inserting the Btus-per-gallon and peak-demand amounts in at different points along the way. If the difference in output is between two models, go with the one with the greater Btu rating to save money. You’ll also need two smaller units that function in tandem if your output is greater than 198,000 Btus, which is the limit for domestic gas heaters.
Btus Output Estimate
Not interested in completing the calculations? Make a rough estimate of how much heater output you’ll want using these statistics.
- The following figures are for one bathroom for one to two people: 140,000 Btus
- Two bathrooms for two to three people: 190,000 Btus
- Three bathrooms for three to five people: 380,000 Btus
Btus Per Gallon by Region
- Kitchen or bath faucets should flow at 1.5–2.2 gpm
- Tub filler faucets should flow at 4 gpm
- Dishwasher: 1–2.5 gpm
- Washing machine: 1.5–3 gpm
- Showerhead should flow at 1.25–2.5 gpm
How to Determine gpm?
To get the real gpm of a fixture, time how many seconds it takes to fill a bucket to the 1-quart mark and multiply that time by the number of gpm. gpm is calculated by dividing 15 by the number of seconds in a minute.
Electric Tankless Water Heater Facts
Thanks to Stiebel and Eltron for their assistance. In addition to gas lines and propane tanks, tankless water heaters operated by electricity can provide the benefits of on-demand hot water to homes that do not have them. Compared to gas or propane tankless heaters, these systems, which heat water using thick copper rods, are significantly quieter and roughly a third smaller in size. And because they do not require vents, they can be fitted practically anyplace, even beneath sinks and in small closets, without compromising performance.
In locations with warm groundwater, that amount of hot water may be sufficient to feed a whole house; but, in colder climates, they are better suited to point-of-use service, where the demand for hot water does not become excessive.
Furthermore, electric heaters have a lifespan that is approximately half that of gas heaters: Warranty periods typically range from three to five years.
As soon as the heating elements fail, it is frequently more expensive to replace the complete heater than it is to simply replace the heating elements.
Tankless Water Heater Installation
Doug Adams created the illustration. What you and your plumber should look for before the installation day is as follows:
Gas Line
If you want your tankless heater to work effectively, you must connect it to a gas supply line that supplies enough volume at a high enough pressure to run the burner. In many circumstances, this will need increasing the diameter of the supply pipe to 3-4 inches in diameter. Furthermore, if the pressure is insufficient, the gas provider will be required to change the regulator on the meter. For your information, some tankless systems, like as ones manufactured by Rheem, are capable of working with a regular 12-inch gas line as long as it is not more than 24 feet in length.
Venting
Tankless gas heaters that do not condense employ stainless-steel vents that can resist high exhaust temperatures. Condensing systems feature a cooler exhaust and use PVC pipes, which are less costly than other types of exhaust. Installing a concentric vent, which has an exhaust pipe inside a larger air-intake pipe, is easier than installing a traditional vent since only one hole in the wall needs to be made. As a point of reference, vent runs have traditionally been limited to a maximum of 10 feet.
Water Hardness
Heat transmission is slowed and water flow is restricted when scale deposits accumulate in a heat exchanger (or on electric heating components) over time. If you currently have whole-house water softening, scale will not be an issue for you. However, if your water is not being softened and its hardness surpasses 120 milligrams per liter, it is worthwhile to invest in a treatment system to remove the hardness. For your information, a specific, point-of-use cartridge, such as the TAC-ler water conditioner (Stiebel Eltron), can be used to change the hardness of water without the use of salt or other chemicals.
Outdoor Tankless Water Heater
Matt Risinger captured this image. If your environment and local rules allow it, think about the advantages of hanging a heater outside in the winter.
- Saves space: You won’t have to create place for another appliance in your home as a result of this. Installation is straightforward: Because of the built-in exhaust vent, there is no need to drill a large hole (or two) through the side of the building. Service is simple: A plumber may come to your home at any time, whether or not you are there. However, take in mind the following: Regulations governing construction: If you want to install it outside, you may require approval from your local building department. Weather conditions that are cold: Even at temperatures as low as 22 degrees Fahrenheit, internal heaters keep components warm, but exposed water lines must be insulated and covered with heat tape that activates automatically in freezing conditions. Southern states are less concerned about frozen pipes than those located north of the Mason-Dixon Line.
Tankless Water Heater Venting
Carl Tremblay captured this image. Are you in need of assistance with repairs around your home? A house warranty may be of assistance. The This Old House Reviews team has put up some in-depth guidelines that you can read here:
- Home warranty providers that are the best
- Reviews of American Home Shield, AFC Home Club, Select Home Warranty, and Choice Home Warranty are all available.
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.
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°.
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.
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.
Fixture
| 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.
Other Sizing Notes
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 hot water heater. 4.5 gallons per minute would be required from the water heater if a shower and the washing machine were both being used at the same time. Any of these scenarios necessitates the purchase of a hot water heater that is large enough to accommodate or surpass the amount of hot water you require simultaneously.
The intake water to a tankless water heater should not be preheated since tankless water heaters are meant to heat only potable (drinking) water.
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. You can read his rants here, or you can listen to him whine about Austin traffic on Twitter at @Bukowsky. You can also follow him on Facebook.
What Size Tankless Water Heater Do I Need? (For Family Of 2,3,4,5,6)
When it comes to tankless water heaters, one of the most common mistakes is purchasing a device that is not powerful enough to meet all of our hot water demands. You don’t want a tankless heater that’s too little, nor do you want one that’s too large and would waste energy unnecessarily heating your home. 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.
- What is the greatest amount of hot water you require? It’s important to know how much water per minute (measured in gallons per minute, or GPM) a particular tankless water heater can heat up, as well as how many degrees it can heat it up by.
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 |
A tankless water heater with a minimum flow rate of 5 GPM and a maximum temperature of 110 F will be required if you are having a shower (with 100 percent flow and 110 F hot water) and concurrently using two faucets (with 100 percent flow and 110 F hot water). 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 rises in direct proportion to the capacity of the unit.
If you have a larger need (8 GPM or more), you should choose one of the finest gas tankless hot water heaters available.
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.
- That represents an additional 40 degrees Fahrenheit differential that a tankless water heater must overcome.
- Because the input temperature is 77 degrees Fahrenheit in Texas, we can really obtain 10 GPM of 110 degrees Fahrenheit water.
- In Minnesota, on the other hand, the inlet water temperature is 37 degrees Fahrenheit.
- You don’t come from Minnesota or Texas, do you?
- 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.
- 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.
- In New York, the heater must contend with an additional 25 degrees Fahrenheit.
- 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. Another useful piece of information about propane units is how much propane is consumed by these on-demand hot water heaters.
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.
Unfortunately, the confidence ranges are extremely wide.
| Number Of Family Members: | Gas Tankless Heater Size (GPM) | Electric Tankless Heater Size (kW) |
|---|---|---|
| What size tankless water heater do I need for afamily of 2? | 6-8 GPM | 10-18 kW |
| What size tankless water heater do I need for afamily of 3? | 7-9 GPM | 15-23 kW |
| What size tankless water heater do I need for afamily of 4? | 8-10 GPM | 20-28 kW |
| What size tankless water heater do I need for afamily of 5? | 9-11 GPM | 25-34 kW |
| What size tankless water heater do I need for afamily 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).
- 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.
- Check here to see if investing in an energy-efficient tankless water heater is truly worth it (we performed some calculations).
- 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.
- 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.
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. In order to replace a 50-gallon water heater, you would require, approximately speaking, the following items:
- If you live in the northern region of the United States, you should have a 10 GPM gas tankless water heater or at least a 27 kW electric tankless water heater. If you live in the southern region of the United States, you should have a 7 GPM gas tankless water heater or at least an 18 kW electric tankless water heater.
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: Rinnai’s gas tankless versions are available in a variety of sizes. As previously said, they are considered to be the top gas tankless water heater brand. 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.
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.
Keep in mind that, especially with larger units, tankless water heater circulation pumps can save you a significant amount of money on hot water.
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.
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 Do I Need?
Note from the editors: We receive a commission from affiliate links on Forbes Advisor. The thoughts and ratings of our editors are not influenced by commissions. Unlike traditional tank water heaters, tankless water heaters give continuous hot water to the kitchen and bathroom. For many homes, installing tankless water heaters represents a welcome break from the deplete-heat-wait cycle associated with traditional tank-style water heater installation. However, reducing the tank also implies that the tolerance margins will be reduced to a bare minimum.
Properly sizing the tankless water heater ensures that you will never be without hot water—and that you will not be forced to purchase a system that is either too large or too expensive.
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Price, customer rating, maximum GPM, heating capacity (in BTUs), and Energy Star certification were all taken into consideration while compiling this top-five ranking.
What a Tankless Water Heater Does
Traditional tank-style water heaters, in contrast to tankless water heaters, heat 40 to 50 gallons of water using a gas or electric burner to heat the water. The burner helps to maintain that temperature by turning on and off intermittently when the water temperature lowers. Maintaining the temperature of a pot of water on the stovetop by turning the burner on and off as needed is analogous to this. Tankless water heaters do not store hot water in a reserve tank like traditional water heaters.
- They are energy efficient.
- The majority of homes have one or two tankless water heaters, which are often positioned in the basement, mudroom, utility room, or hallway of the house.
- Customers with tank-style heaters experience the same transient temperature difference as those who use faucet-style heaters because of the distance between the water heater and the faucet.
- The installation of supplemental heat recirculators, which circulate the water in a continuous loop between the faucet and the heater, is an option for certain households.
There are similar systems in hotels that are designed to maintain hot water near the faucet and reduce waste water usage. Some tankless water heaters are equipped with built-in heat recirculation systems.
How to Calculate the Right Size of Tankless Water Heater
Temperature rise is defined as the difference between the groundwater temperature in your location during the winter, or the coldest time of year, and the recommended set temperature of your tankless water heater. To find out what the typical winter groundwater temperature in your location is, look at a map showing average winter groundwater temperatures. Alternatively, during the coldest time of year in your location, you may use a thermometer to monitor the temperature of your water as it is drawn directly from the ground (usually, at an exterior faucet).
Determine Peak Hot Water Demand
When it comes to peak hot water demand, this is the greatest amount of hot water that your home may require at any given time. It is not intended to be a practical figure; rather, it is intended to ensure that your water heater is capable of meeting theoretical peak demands. Bathroom Utilities 2 gallons per minute for the clothes washer Estimate and include the maximum number of services that might be consuming hot water at any given time, such as the following: Shower = 2 gallons per minute 1.5 gallons per minute (gpm) in the kitchen sink Dishwasher = 2 gallons per minute Total flow rate: 5.5 gpm Alternatively, in a household with a large number of individuals who need hot water: Shower = 2 gallons per minute 2 gpm in a tub 1.5 gallons per minute at the bathroom sink 1.5 gallons per minute (gpm) in the kitchen sink Dishwasher = 2 gallons per minute Total flow rate: 9 gpm
Choose a Tankless Water Heater
Tankless water heater manufacturers provide calculation tables or online calculators to assist you in determining the best model for your needs based on peak hot water demand and the temperature rise in your area. For example, if the temperature rise in your area is 60 degrees, your home may have a peak hot water demand of 6 gpm at its highest point. This may direct you to a couple of models that fit the bill in this situation. However, if the temperature rises above 40 degrees Celsius, the manufacturer may recommend completely different models.
You must compare and contrast the two sets of information in order to determine the most appropriate tankless water heater for your home.
Tankless Water Heater Pros and Cons
- When compared to huge tank models, little units take up less room. There is no need to wait for the hot water to cycle because there is continuous hot water. Because of the elimination of standby hot water, there will be no unnecessary heating of water.
- There is no hot water stored in reserve in case the electricity goes out
- When all aspects are taken into consideration, it does not cost less than tank models. Excessive scaling as a result of the extremely hot burner, resulting in a larger requirement for routine maintenance
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Tankless Water Heater Buying Guide
Tankless water heaters create more hot water while using less energy than the most efficient tank heaters, allowing you to save on energy, space, and money all while saving money and time.
Tankless Water Heaters
A tankless water heater, also known as an on-demand water heater, warms water only when it is required. It is possible to put these heaters in a closet, on an outside wall, or in any other suitable location within your home. They may be used to heat your entire home or just a single point of usage such as a shower, sink, or appliance, among other things. A tankless water heater, whether natural gas, propane, or electric, provides you with an infinite supply of hot water while saving you money on energy expenditures by eliminating the need to store, heat, and reheat the same tank of water.
While the initial purchase and installation are more expensive, most homeowners discover that they save enough money on their energy bills that the device pays for itself within a few years.
How Does a Tankless Water Heater Work?
- When you turn on a hot water faucet or turn on the dishwasher, the tankless water heater identifies the requirement for hot water and begins the heating process immediately. In order to provide water at the correct temperature, the temperature of the entering water is utilized to determine the amount of heat that must be produced by the burners. When there is no longer a demand for hot water, the unit shuts down and stops consuming energy, waiting until a new demand for hot water arises. The ultimate result is hot water that is not restricted to the amount of hot water stored in your tank.
Benefits of a Tankless Water Heater
You have the ability to convert any water source into hot water on demand. There is no limit to the quantity of heat that may be stored in a storage tank heater. Whether you’re cleaning the dishes, washing your clothes, taking a hot bath, or even doing them all at the same time, tankless water heater technology will provide you with the hot water your lifestyle requires immediately and efficiently.
Lower Energy Bills
When you use a tankless water heater, you may save up to 40 percent on your energy bills! Heat-only units are meant to be extremely energy efficient, heating water only when it is required.
Longevity
Tankless water heaters have a lifespan of up to 20 years, which is often twice as long as a traditional tank-style device.
Space Savings
Traditional water heaters may consume up to 16 square feet of important floor space, which is a significant amount of room. Many tankless water heaters are roughly the size of a carry-on suitcase and may be mounted on nearly any wall inside or outside your home, depending on your preferences.
Clean, Fresh Water
Traditionally installed water heaters are susceptible to rust and scale buildup within the tank where the hot water used for bathing and drinking is kept. Water heaters that do not require a tank provide you with continuous access to fresh, clean water that is heated on demand as it goes through the unit.
Choosing the Right Tankless Water Heater
It is critical to determine the size of the tankless water heater you will require. A heater that is too tiny will not be able to appropriately fulfill the hot-water demands of your house, while a heater that is too huge will be an unnecessary expense. How much water will you use at peak demand – for example, when the dishwasher is running, you are having a shower, and a load of laundry is being washed? What proportion of the incoming water will need to be heated in order to meet the demand? Before purchasing a tankless water heater, you should think about two things: the flow rate, which is the amount of water that flows through a fixture or appliance in gallons per minute (GPM), and the temperature rise, which is the difference between the groundwater temperature and the desired hot-water output temperature.
For example, you may be using the kitchen sink, washing laundry, and bathing all at the same time.
To find out the flow rate of a fixture or appliance (shower head, dishwasher, washing machine, and so on), consult the manufacturer’s handbook or look for the GPM stamped directly on the fixture or appliance.
Average GPM Usage for Common Appliances and Fixtures
It can be seen from the graph above that when the shower, kitchen sink, and high-efficiency washing machine are all in use at the same time, the total flow rate is 6.0 GPM.
Depending on where you live, groundwater temperatures can range anywhere from the mid-30s to the upper 70s degrees Fahrenheit, measured in Fahrenheit. Groundwater temperatures in North America are divided into three climatic zones, each with its own average groundwater temperature:
- Northern Zone temperatures range from 37 degrees to 51 degrees
- Central Zone temperatures range from 52 degrees to 61 degrees
- And Southern Zone temperatures range from 62 degrees to 77 degrees.
The average interior water temperature in a residence is between 110 and 120 degrees Fahrenheit. For the temperature rise, subtract the entering water temperature from the required interior water temperature to find the temperature increase. According to this formula, if your shower water temperature is 57 degrees Fahrenheit and your ideal shower temperature is 120 degrees Fahrenheit, the temperature rise is 63 degrees. Additionally, while purchasing a tankless water heater, in addition to being aware of the flow rate and temperature rise, you should consult size tables to assist you in selecting the most appropriate heater for your requirements.
Point of Use Water Heaters
Temperatures in the interior of a typical home range from 110° to 120° Fahrenheit. For the temperature rise, subtract the entering water temperature from the required internal water temperature to find the temperature rise. For example, if the entering water temperature is 57 degrees and the targeted shower water temperature is 120 degrees, the temperature rise will be 63 degrees as a result of the shower. Tankless water heaters are available in a variety of sizes, and in addition to knowing the flow rate and temperature rise, sizing tables may help you choose the most appropriate model for your requirements.
Hybrid Water Heaters
The average interior water temperature in a residence varies from 110 degrees to 120 degrees Fahrenheit. To calculate the temperature increase, subtract the entering water temperature from the required interior water temperature. Using the above example, the temperature rise is 63 degrees when the entering water is 57 degrees and the required shower water is 120 degrees. When purchasing a tankless water heater, in addition to knowing the flow rate and temperature rise, you should consult size tables to assist you in selecting the most appropriate heater for your needs.
What Size Tankless Water Heater Should You Buy: Sizing For Your Family Needs
Tankless water heaters are the way of the future when it comes to hot water usage in residential and commercial buildings. Tankless water heaters are characterized by their small form and ability to provide hot water on demand. On the other hand, on-demand does not always imply continuous service. Flow rate is the amount of water that may be produced in one minute by a tankless water heater (both electric and natural gas). If the demand for hot water in your household exceeds the capacity of your water heater, you may experience a lack of hot water.
- Gallons per minute (GPM) is the unit of measurement for tankless water heaters (GPM).
- During peak hours, the average family consumes around 6.5 GPM.
- A tankless water heater with a capacity of 4 GPM can deliver enough water for one shower and one appliance to run at the same time.
- When a tankless water heater is undersized, it will not be able to provide enough hot water to fulfill the needs of your household.
- A tankless water heater with a flow rate of 4GPM will be unable to heat enough water to fulfill this demand for hot water.
- A lar ge tankless water heater has greater installation and operating expenses than a traditional tank water heater.
- For example, a 4 GPM tankless water heater will cost between $400 and $700 plus installation, and an 8+ GPM tankless water heater would cost between $900 and $2000 plus installation.
- Hot water on demand is defined as having continuous hot water output for the duration of time that the hot water tap is open.
- If you have too many hot water faucets open at the same time, the water will become lukewarm if the tankless water heater’s output capacity is surpassed.
- Installation costs are in addition to the cost of the tankless water heater.
We’ve put together this complete shopping guide to assist you in making the best decision for your family when it comes to tankless water heaters. The following section will lead you through the many various considerations you should make while shopping for tankless water heaters.
Gallons of Hot Water You Need for a Tankless Water Heater
The first thing you’ll need to think about is how much hot water you’ll require from your tankless heater. In most cases, we refer to this as “sizing,” although you will not be using dimensional measures to determine the appropriate size for your tankless water heater. Instead, you’ll need to pay attention to two separate metrics: the flow rate and the temperature rise (or decrease).
Tankless Water Heaters GPM Flow Rate Explained
It is the time of day when you use the most hot water at one time that is referred to as peak demand. Tankless water heater size is determined by the flow rate, which is measured in gallons per minute (GPM). The majority of tankless water heaters are capable of producing between 2 and 10 gallons of water per minute on average. During peak demand periods, it will be necessary to total up all of the flow rates of the fixtures and appliances in your home that may be using hot water at the same time in order to establish your water flow rate need during those times.
However, the following list of normal flow rates for popular fixtures and appliancesshould assist you in making an estimate:
| Fixture or Appliance Usage: | AverageGallons per Minute(GPM) Used |
|---|---|
| Bathtub | 4 GPM |
| Rainhead shower head | Up to 5 GPM |
| Standard shower head | 2.5 GPM |
| Standard dishwasher | 2.5 GPM |
| High-efficiency dishwasher | 0.5 – 1.5 GPM |
| Standard clothes washer | 2.5 GPM |
| High-efficiency clothes washer | 1.0 GPM |
| Sink faucet | 1.5 GPM |
Using the expected GPM production as a guideline. There are some fixtures and appliances that have a larger output than others. Using a normal shower head (2.5 GPM) consumes approximately half the amount of hot water as using a rainhead shower head, as seen in the following table (5.0 GPM). The kitchen faucet consumes approximately the same quantity of hot water as other sink faucets, regardless of where they are installed. It is uncommon for many sink faucets to function in tandem for extended periods of time.
What is a Tankless Water Heater’s Temperature Rise
Once you’ve determined the amount of water flow your tankless unit will require during peak demand periods, you’ll need to figure out how much “temperature increase” it will require. The temperature rise refers to the amount of degrees your hot water heater will need to raise the incoming average groundwater temperature in order to supply enough hot water for your household. For example, suppose the temperature of the entering cold water is 52 degrees Fahrenheit. If you want hot water that is 110°F, you’ll need a temperature raise of 58°F.
Putting Flow Rate and Temperature Rise Together
The flow rate and temperature rise of a water heater are both measured in the ratings. If you want to appropriately size your water heater, you must take into consideration both the flow rate necessary and the rise in temperature required.
| Ground Water Temperature | Expected Gallons per Minute Output |
|---|---|
| 37 F | 3.9 GPM |
| 42 F | 4.7 GPM |
| 47 F | 5.5 GPM |
| 52 F | 6.3 GPM |
| 57 F | 7.1 GPM |
| 62 F | 7.8 GPM |
| 67 F | 8.6 GPM |
| 72 F | 9.4 GPM |
Another example is based on a tankless water heater with a 9.5 GPM output and a temperature rise of 35 degrees. Consider the following scenario: you have four gadgets that may all demand hot water at the same time:
- 1 GPM / 110° for the hot water faucet
- 1 GPM / 110° for the dishwasher
- 2 GPM / 120° for the washing machine.
Furthermore, let’s say that the entering cold water temperature is 50°F. A tankless water heater with a flow rate of 5.0 GPM and a temperature increase of 70° would be required to run all of these devices at the same time. The total flow rate of 5.0 GPM is equal to the sum of all device flow rates combined. The temperature increase of 70 degrees Celsius is obtained by subtracting the entering water temperature (50 degrees Celsius) from the highest device water temperature (120 degrees Celsius).
If you don’t intend to use all of your hot water equipment at the same time, you may save money by purchasing a less costly heater with a lower flow rate instead of an expensive one.
Are Tankless Water Heaters Worth the Cost
When it comes to purchasing a tankless water heater, many individuals question if the investment is worthwhile. Tankless water heaters, in contrast to tank water heaters, are a good investment because of their longer lifespan, lower maintenance requirements, and ability to provide continuous hot water on demand.
- Tankless water heaters have a lifespan of up to 20 years, whereas tank water heaters have a lifespan of as short as eight years. Due to the fact that tankless water heaters do not have a tank that might malfunction and leak, the danger of water damage is reduced
- Tankless water heaters do not require any maintenance because they do not have a tank. Tank models require yearly flushing maintenance to maintain the tank’s integrity, which is commonly neglected, resulting in a shorter tank’s lifespan as a result. Tankless water heaters have the ability to produce hot water on demand when needed. A 50-gallon tank water heater can get depleted in as short as 30 minutes of continuous usage and requires a minimum of one hour of recovery time
- However, this is not the case.
Electric vs. Gas Tankless Water Heaters
While tankless water heaters have a lifespan of up to 20 years, tank water heaters have a lifespan of just 8 years. Due to the lack of a tank that might break and leak, tankless water heaters reduce the likelihood of water damage. There is no tank to maintain with a tankless water heater. For tank types, yearly flushing maintenance is required to keep the tank in good condition. This maintenance is frequently neglected, which contributes to the tank’s shorter lifespan. Hot water may be provided on demand via tankless water heaters.
Electric Tankless Water Heaters Cost Less to Buy and Install
It is one of the key advantages of purchasing an electric tankless water heater over purchasing a gas-powered tankless water heater because they are less expensive. Tankless electric water heaters for the entire house normally cost between $500 and $700, but whole-house tankless gas water heaters cost between $1,000 and $1,200 or more. Aside from that, the cost of installing an electric tankless heater is much lower than the cost of constructing a gas-powered tankless heater. Following your confirmation that your home’s wiring is suitable with the type you’ve chosen, installing the electric heater should be a reasonably simple and quick task to complete.
In order to work, some electric water heaters require up to four 220v breakers, which dramatically increases the expenses of installation and operating.
For starters, you’ll need to build a ventilation system to safely exhaust any fumes that your water heater may produce.
Electric Tankless Water Heaters are Easier to Maintain
Because electric units are simpler devices than gas-powered units, they are less expensive than gas-powered units. Because there are fewer components within, there are fewer moving parts that might break down and necessitate a costly repair job. The cost of fixing a propane-powered device is often cheaper than it would be if the equipment were fueled by gas. The majority of tankless water heaters will beep to alert you when tankless water heater maintenance is required.
Electric Tankless Water Heaters are More Energy-Efficient
The most efficient gas-powered tankless heaters have an energy efficiency of around 85%. When compared to most electric vehicles, which have an average energy efficiency of 98 percent, an 85 percent efficiency rating is considered inadequate. So even though natural gas is less expensive than electricity in your location, choosing an electric unit may result in you saving money on energy expenditures in the long run. Electric heaters are more ecologically friendly than other types of heaters.
The production of electricity is already less detrimental to the environment than the combustion of natural gas, and the greater energy efficiency of electric vehicles further adds to the disparity between the two modes of transportation.
Electric Tankless Water Heaters Can Require Significant Electrical Upgrades
Gas-powered tankless heaters with the highest energy efficiency average around 85 percent. When compared to most electric vehicles, which have an average energy efficiency of 98 percent, an 85 percent efficiency rating is considered bad. It is possible that by choosing an electric unit, you may save money on energy expenditures even if natural gas is more affordable than electricity in your location. Environmentally friendly electric heaters are available. Already, the production of electricity is less destructive to the environment than the combustion of natural gas, and the greater energy efficiency of electric vehicles further adds to the disparity between the two options.
Gas Tankless Water Heaters Produce More Hot Water
A variety of natural gas and propane types are available for tankless gas water heaters. Some purchasers choose a tankless gas water heater over an electric water heater because gas versions can handle higher flow rates than electric water heaters. The best electric units have a maximum flow rate of 8GPM, but some gas ones have a flow rate that is substantially greater. In the case of a big home or an industrial application, you may be forced to choose a tankless heater that is fueled by natural gas.
The majority of on-demand tankless water heaters are capable of operating at a variety of intake temperatures.
In an electric model, the same rise in temperature of 70 degrees Fahrenheit (70 degrees Fahrenheit) will result in around 2 gallons of hot water per minute in hot water, which is a considerable drop in production.
Natural Gas is Cheaper than Electricity in Some Areas
Given the price disparity between natural gas and electricity, depending on where you reside, a gas-powered device may be more appealing than an electric model. However, even if natural gas is much less expensive than electricity, the gain in efficiency associated with electric models, as well as the anticipated increase in natural gas pricing, may still make turning electric the most cost-effective alternative.
Indoor or Outdoor Installation Options
In contrast to a standard tank-style water heater, which must be installed indoors, tankless water heaters may be installed either indoors or outdoors. Installation of your tankless water heater outside has the primary advantage of eliminating the need to install a venting system inside. Because electric units do not require ventilation, placing them outside provides no meaningful advantage in terms of energy savings. In warmer areas, it is possible to put a tank-style water heater outside; however, you will still need to construct an enclosure around it.
The majority of outdoor tankless water heaters include built-in freeze protection that can withstand temperatures as low as -30 degrees Fahrenheit.
Conclusion
Although you may not give it much thought, you use your hot water heater on a regular basis. Providing hot water whenever you need it is the one item that helps keep things clean and operating smoothly in any household! The question is, how do you choose the appropriate size tankless water heater for your household? Take into consideration the appliances that will be used at the same time. When two persons living in an average-sized home need to shower every day at different times of the day (for example, because they work opposing shifts), a 2 GPM model would be appropriate.
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