- Fuel Source. Water heaters come in standard electric, heat pump, natural gas or propane fuel sources. Electric water heaters rely on an electric element much like an electric stove. The element heats up to warm the water. This is called resistance heating. Heat pump water heaters use a process much like a reverse air conditioning system. A closed loop refrigerant system removes heat from the atmosphere and conveys it to the tank by use of a compressor and refrigerant. Heat pump water heaters can use about a 1/3 of the electricity over a standard electric water heater. Natural gas and propane water heaters use the burning of fossil fuels to generate the heat which is radiated from the combustion through the inner walls of the tank to the water.
- Tank capacity. Water heaters range from 20-gallon sizes up to 80-gallon sizes for most residential applications. The capacity of your water heater is roughly determined by the expect volume of hot water use for the home. You can always increase the capacity with a new water heater if you feel you sometimes run out of hot water due to the number of family members in the home.
- Size. We are talking actual dimensions. Height and width vary tremendously. There are tall boys, low boys, fat boys. The proper dimensions will be determined by the location where the tank will be installed. Some capacities come in all different sizes. For instance, you can get a 50-gallon tank in just about any configuration. Check to make sure it will fit with the proper manufacturer’s clearances.
- Venting for gas water heaters. Here is something you may not have considered. There are several venting options as well. There is the top vent natural draft, the top vent direct vent, and the top vent powered vent. Each is determined by the venting requirements of the building. Natural draft usually requires a double wall B-vent flue that extends through the roof line for proper updraft to take place. A Direct vent is a concentric, usually flexible, vent that can be angled to the side of the house. The vent contains the inner tube for the combustion gases and an outer tube for the fresh air. The power vent uses an electric induced draft motor to force the flue gases out of the house and is connected with PVC pipe for the vent tubes. The powered vent requires an A/C outlet and a condensate drain.
- Tankless. Tankless water heaters come in several varieties as well. The choices for a tankless will be discussed in a separate article.
So remember, when shopping for a new standard water heater, make sure you have the fuel type, capacity, size, and venting requirements before you select your replacement.