Solar Hot Water

How Solar Hot Water Works

What is solar hot water?

Solar hot water heater is a hot water system that uses energy from the sun to heat your home’s water. Solar collectors, mounted on the roof or ground next to a home, absorb heat from the sun and transfer it through a fluid loop into a solar storage tank (typically located in the basement or mechanical room) that stores preheated water. This heated water is then piped throughout the home to showers, dishwashers, sinks, and washing machines. Solar hot water systems can also be used for pool heating and for space heating.

Due to Massachusetts’ location, collectors work most efficiently when they are oriented as close to due south as possible and tilted around 40 degrees to the horizon. Collectors should receive at least 5 hours of unobstructed sunlight each day and be at least 75% shade free.

Hot Water Tank

Solar Hot Water Collectors

Solar hot water systems are typically sized to provide up to 80% of a home’s annual domestic hot water needs. Since the sun is stronger in the summer, the solar hot water system can provide for all of a home’s domestic hot water needs during that season. In the winter, when the days are shorter, a backup heat source (often an electric resistance heating element) is used to provide additional hot water to meet 100% of a home’s hot water needs.

There are two main types of solar hot water collectors:

Glazed flat plate collectors are collectors that look similar to solar photovoltaic (electricity) collectors. They have a clear glass or plastic casing over the collector that traps heat like a greenhouse. Flat plate collectors can operate at a wide range of temperatures.
Evaporated tube collectors are collectors with thin, copper tubes filled with fluid. This fluid is inside larger vacuum-sealed clear glass or plastic tubes. Evaporated tube collectors typically perform better during the winter than flat plate collectors, but they are not as efficient at all temperatures.