Water Heaters

Getting the Most From Your Water Heater

Modern lifestyles depend on an ample supply of hot water. With a properly sized electric or LP gas water heater, you will have an abundant supply of hot water to meet your needs.

Things to Consider

Water heaters should be installed to meet codes and manufacturers recommendations for proper operation and safety. In North Carolina the water heater thermostat is pre-set at 120°F.

When choosing a storage type water heater, select one to meet your highest one-time demand (first hour rating).

In larger homes two smaller heaters may meet your needs better than one large unit.

Select models with a higher energy factor (EF) to reduce operating cost. The Federal Trade Commission requires an energy guide label on each residential gas, oil and electric storage type water heater. The label shows estimated annual heating cost based on the heater capacity, EF rating and cost of fuel.

Locate water heaters in a conditioned area where possible. Hot water pipes should be insulated throughout the house for efficiency.

Water Heater Selection & Size Guide

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).