How to Select a Tankless Water Heater

How to select a tankless water heater can be challenging. The key to finding the right tankless water heater unit is to know how to choose a flow rate. Compare and contrast flow rates of different tankless water heater models after you have done some howework. It all begins by calculating your peak hourly hot water demand. Here's a way to do it.

Estimating Peak Hourly Hot Water Demand

To estimate your household’s peak hourly hot water demand, determine what time of day (morning or evening) your family is likely to require the greatest amount of hot water from a tankless water heater. Then calculate the maximum expected hot water demand using the table below.

Water-using activity
Avg. gallons hot water per usage
 
Times used in hour
 
Gallons used in hour
Showering
20
x
__________
=
__________
Bathing
20
x
__________
=
__________
Shaving
2
x
__________
=
__________
Washing hands/face
2
x
__________
=
__________
Hand dishwashing
4
x
__________
=
__________
Auto dishwashing
10
x
__________
=
__________
Preparing food
5
x
__________
=
__________
Auto clothes washing
32
x
__________
=
__________
Peak Hour Demand
=
__________
 
Example:
3 showers
20
x
3
=
60 gals/hour
1 shave
2
x
1
=
2 gals/hour
Handwash dishes
4
x
1
=
4 gals/hour
Peak Hour Demand
=
66 gals/hour

Source: Gas Appliance Manufacturers Association and ACEEE estimates

Note: This does not provide an estimate of your family’s total daily use, only the peak hourly use. Also, the values in this table do not consider water conservation measures, like low-flow showerheads, faucet aerators, frontloading clothes washers, etc. that can reduce hot water use for each activity.

Additional Tankless Water Heater Measurements

  1. Find out your ground water temperature of the water coming into your tankless water heater unit. A plumbing expert in your area can tell you this.
  2. Determine your outgoing temperature. How hot do you like your water?

Once you figured out the peak demand, ground water temperature, and your desirable outgoing temperature, choose a tankless water heater model that meets your need. Start shopping by choosing one of the tankless water heater resources on the left and right side of the pages.




Tankless Water Heaters | How to Select a Tankless Water Heater | How Tankless Works | Tankless Benefits