Direct vs. Indirect Solar Water Heaters

Design

• Direct solar water heating systems run the same water through the solar collector that the resident will use for drinking or bathing. The sun's rays heat the water, which then goes into a storage tank. In indirect systems, the fluid heated by the collector never leaves its tubing, moving instead through an exchanger coil that heats a separate water supply.

Environmental Factors

• Direct solar heating systems work best in climates that do not experience regular freezes, since frozen water could damage the collector. Indirect systems that mix glycol with the water in the exchanger make a better choice for cold climates.

Considerations

• Direct solar heating systems work best in areas boasting relatively "soft" or mineral-free water. "Hard" water supplies that leave calcium deposits on machinery function better with the closed-loop design of an indirect system.