A water heater converts energy to heat and transfers that warmth to water. It’s connected to a cold water supply pipe and has an outgoing hot water pipe, or system of pipes, that supplies heated water to one or more taps and appliances.
A conventional water heater stores heated water in its tank. The less common tankless water heater doesn’t store water; instead, it routes heated water straight to taps or appliances.
Most water heaters are fueled by natural gas, although solar, propane and electric water heaters are not unusual. For homes that use a large amount of hot water and receive full sun year-round, a solar water heater may be economical. After all, water heating is the second largest energy user in most homes, right after space conditioning.
How it works
Solar water heaters help conventional water heaters. Water enters a conventional water heater at 50°F to 60°F, and the water is then heated to the desired temperature. With a solar system, cold water goes first to the solar collector, where it is naturally warmed by the sun. Then it goes to the water heater tank. If the water already is hot enough, the conventional water heater just stores the hot water. If the water is too cool, the conventional water heater warms it up.
What size tank
The number of bathrooms in the house can typically measure the needed tank size, though some circumstances can affect these standards, such as a family with heaps of laundry or a house with an especially large bathtub.
Minimum size unit for a 1-bathroom house should be 30 or 40 gallons, in either gas or electric. For a 1 1/2-bath house, 40 gallons is minimum. For a 2- to 3 1/2-bath house, choose a 50-gallon gas heater or a 66- to 80-gallon electric one (because electric water heaters take longer to heat water, large tanks should be bigger than their gas-fired counterparts). For a large, 4-bath house or a home with an extra-large bathtub get a 75-gallon gas heater or a 120-gallon electric heater.
There are three basic solar water heater systems. Active systems use pumps to move the heat transfer fluid, thermosiphon systems, which allow the heated water to rise from the collector to the storage tank, and full batch systems, in which the solar collector is the water tank.