Solar hot water technology available today is tested and reliable. 

Solar hot water components. A solar hot water system will contain the following major components.

Solar Collectors use the sun’s energy to heat either water or a heat-transfer fluid.  Two common types of collectors are: 

• Flat Plate Collectors use an insulated box with a transparent cover (called the glazing) to house flow tubes on a dark colored absorber plate.  These are the most commonly used collectors and can heat the collector fluid to 180°.
• Evacuated-tube Collectors use parallel rows of transparent, air-less glass tubes, each of which contain an absorber fin attached to a flow tube.  New designs have reduced the cost of this technology and they can achieve temperatures up to 350°.  

Storage Tanks store heated water for later use. Insulation assures efficient use of stored fluids. 

A Conventional Backup supplements your hot water supply when you need more hot water than your solar system provides. 

Solar hot water systems. Systems are either active or passive. Active systems use pumps and controls to circulate the water or heat-transfer fluid. Passive systems rely on gravity and thermal dynamics to drive circulation. Solar hot water systems should be protected from the effects of freezing weather, which Berkeley usually experiences at least once a winter. System equipment must be certified by the Solar Rating Certification Corporation (SRCC) to qualify for the Federal Income Tax Credit. The following two active system types meet both these criteria.

Closed-loop Glycol Systems use glycol, a non-toxic anti-freeze, as the heat-transfer fluid in the collectors.

Drain-back Systems use water as the heat-transfer fluid. When water is not being circulated in the collector it drains into a reservoir tank to provide with freeze protection to the system.

Other systems may meet your specific solar hot water needs.  Among these are direct-circulation systems, integral collector-storage systems and thermosyphon systems.