Water Heater Selection Guide
Selecting the Right Size Water Heater for Your Home:
FIRST: Find the right size water heater for your needs by finding models with a First Hour Rating that matches (within one or two gallons) your peak hour demand.
To estimate your peak hour demand:
1. Determine during what general time of day (morning, noon, evening) there is usually the most use of hot water in your home, keeping in mind the number of people in your home.
2. Using the following table, determine what your maximum usage of hot water in one hour could be; this is your peak hour demand.
NOTE: This table does not estimate total daily hot water usage. As an example, an average of 4 gallons of hot water is used each time dishes are washed by hand, but dishes washed by hand are usually done 3 times a day. The average daily hot water usage for hand dishwashing, 12 gallons, is about the same as the average hot water usage for an automatic dishwasher, used once a day.
Use |
Avg. gal. of hot water |
|
# per hour |
|
Gallons used in one hour |
| Shower |
20 |
x |
|
= |
|
| Bath |
20 |
x |
|
= |
|
| Shaving |
2 |
x |
|
= |
|
| Hands & face washing |
4 |
x |
|
= |
|
| Hair shampoo |
4 |
x |
|
= |
|
| Automatic dishwasher |
14 |
x |
|
= |
|
| Food Preparation |
5 |
x |
|
= |
|
| Automatic clothes washer |
32 |
x |
|
= |
|
| |
TOTAL (Peak Hour Demand) |
|
EXAMPLE: Your household uses the most hot water in the morning. In the busiest one-hour period of the morning, the usage is:
| 3 showers |
20 x 3 = 60 |
| 1 shave |
2 x 1 = 2 |
| 1 shampoo |
4 x 1 = 4 |
| Hand washing of dishes |
4 x 1 = 4 |
| |
| (Peak Hour Demand) |
70 |
In this case, the peak hour demand is 70 gallons and you should look for those models of water heaters with a first hour rating of 68 to 72 gallons.
NOTE: This sizing guide is from the Consumers Directory of Certified Efficiency Ratings for residential heating and water heating equipment and is provided with permission from GAMA (Gas Appliance Manufacturers Association).
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