Solar hot water systems

Solar hot water systems: Solar hot water heaters use the warmth of the sun to heat either water or another fluid in collectors. A typical system may reduce the need for conventional water heating by about two-thirds. When the plumbing from a solar heater connects to a house's existing water heater, the traditionally fueled heater will be inactive as long as the water coming from the solar system is as hot or hotter than the temperature setting on the traditional system.

When the temperature falls below that level, the home's water heater can kick in to ensure an ample supply of hot water.

What does a solar hot water system do?

The main function of a solar hot water system is to heat or preheat water so that the sun is doing the work that would otherwise be done by fuel oil, electricity or natural gas. How does a solar hot water save money? Water heating is a typical household's second-highest energy cost. The primary cost of the solar hot water system is putting the system in place.

Unlike other hot water systems that cost money to install and then have additional fuel costs (gas, electricity or heating oil) for the operation of the system, solar hot water systems operate by the power of the sun. Thus, the “fuel” for the system is free. Some maintenance may be necessary.

How does it work?

Solar hot water systems need an unshaded, preferably south-facing location, most commonly a roof. Most solar hot water systems have two parts: a solar collector and a storage tank. The collector is usually mounted on the roof and carries the fluid - water or an antifreeze solution - to be heated. The tubes attach to an absorber plate, which is painted black to absorb heat. As heat builds up in the collector, it heats the fluid passing through the tubes. The storage tank then holds the hot water. Storage tanks can be just a modified water heater, but are usually larger and very well insulated. Systems that use fluids other than water usually pass through a coil of tubing in the water tank. The coil heats the water for use.

Paybacks vary widely, but expect a payback of 4 - 8 years on a well-designed and properly installed solar water heater.Shorter paybacks are possible in areas with higher energy costs. After the payback period, savings continue for the life of the system, which ranges from 15 to 40 years, depending on the system and how well it is maintained.

Federal and state tax incentives may further reduce the cost of installing a system.

The Energy and Small Farm Sustainability program is made possible by funding from Northeast Sustainable Agriculture Research and Education program.

Adapted from U.S. Department of Energy, EREE office and from the National Renewable Energy Laboratory, U.S. Department of Energy.