Using sunshine to heat or preheat your water can cut your annual hot water costs in half. An ENERGY STAR certified solar water heating system can cut your annual hot water costs in half, and is generally designed for use with an electric or gas back-up water heater.
Current Specification Effective Date: January 2009
The specification covers high-efficiency gas storage, whole-home gas tankless, solar, and high efficiency electric storage water heaters. Products must meet minimum requirements for energy efficiency, hot water delivery, warranty period, and safety.