Solar Water Heaters

Solar Siting

Siting solar collector panels properly for optimum collection makes an enormous difference in the amount of energy you'll save. Solar collectors should be aimed true south and tilted at an angle between 18 and 50 degrees. If your roof doesn't have a southern exposure, you'll need to build a frame for the collectors that is perpendicular to your roof-line to maximize exposure. When choosing the site for your collectors, avoid anything that might block the sunlight, like trees, chimneys or other buildings. EWEB and EPUD customers can receive free solar site analysis.


Each system has its own maintenance requirements, and some need more maintenance than others. Ask about maintenance requirements before you buy.


Maximize the efficiency of your system by insulating pipes and storage tanks, setting the thermostat on your water heater to 120 degrees, and using low-flow showerheads.

Passive Solar Water Heaters

Passive solar water heating systems do not require an auxiliary source of power to deliver solar heated water to your faucet. There are no pumps or electronic controls.

The following types of systems are available locally:

Thermosyphon System

A thermosyphon-type solar water heater has an insulated water storage tank mounted above flat plate solar collectors. The collectors transfer heat from the sun to an antifreeze collector fluid. The hot collector fluid flows though a heat exchanger wrapped around the water storage tank, heating the household water inside the tank. The collector fluid then flows back down into the collectors. Whenever hot water is used, solar heated water is drawn from the storage tank into the electric water heater. The Solahart is available locally.

Batch System

In a "batch" heater, household water is stored in a series of metal tubes enclosed in glass tubes. The sun shines on the tubes and warms the water inside. Like the thermosyphon system, the solar heated water in the tubes is drawn into the electric water heater when hot water is used.

Active Solar Water Heaters

Active systems use solar collectors to gather the sun's heat. These systems also incorporate sensors that control the system's operation. When the solar collectors in an active system reach a preset temperature, a sensor signals an internal pump to circulate heat transfer fluid through the collectors. The fluid collects the sun's heat and transfers it to the water. When there is enough hot water in the storage tank, or if the outdoor temperature drops to near freezing, the sensor signals the pump to stop and the fluid in the collectors drains back to a small holding tank. This process, called "drainback," protects the collectors from freezing.

Drainback System

The following systems are available locally. Each incorporates the drainback system:

* Solar Skylight uses a single, large flatplate collector that is equipped with a plastic heat absorber.

* The Sun-Pak incorporates two flatplate collectors with copper plates for heat absorption.

* Thermomax uses a series of smaller, vacuum-insulated, tubular solar collectors with copper absorber plates.