When you are considering purchasing a conventional storage type water heater, be sure to choose one with the proper capacity. A water heater that is too small will not be able to keep up with the demand for hot water and a water heater that is larger than necessary will be inefficient and cost more to operate.
A conventional tank type water heater keeps a full tank of water hot 24 hours a day. Hot water is always available when needed, but a lot of energy is wasted keeping the water hot when it will not be needed for hours. Called standby heat loss, the problem is worse the bigger the tank is. Accordingly, you can minimize standby heat loss by purchasing the smallest sized water heater that will meet the demand.
Experts recommend using the “first hour rating” rather than tank size when selecting a storage type water heater. The first hour rating is an indication of how much hot water a water heater can supply in one hour starting with a full tank of hot water.
Obviously, the size of the tank will affect the first hour rating but in addition, a water heater that can heat water quickly will have a higher first our rating than a water heater that heats water more slowly. The type of fuel (electric, natural gas, propoane, etc.) and the size of the heating element determine the rate at which a water heater can heat water.
The Department of Energy publishes tables that you can use to estimate your peak hourly demand for hot water. Once you estimate your peak hourly demand, select a water heater that has a first hour rating within a couple gallons of that amount.
