About solar Hot Water: For hundreds, perhaps thousands of years, humans have heated water with sunshine simply by leaving a bucket of water in the sun. It takes a lot of energy to heat water. Typically, up to 30% of a home’s energy consumption is used just to heat water for bathing, laundry and cleaning.  By installing a solar hot water system, homeowners may shave off 200 to 500 kilowatt-hours per month off their electric bill, thereby saving money and reducing pollution at the same time. Installing a solar hot water system is typically the first and most cost-effective step when turning to the sun for energy. Even if a photovoltaic system is your primary interest, a solar (thermal) hot water system along with a PV system will provide the best economics and space-efficiency on your roof.

The type of solar water heating system chosen will largely be determined by your climate as freezing temperatures may damage components. Technology for solar thermal has had great innovations in the recent decade bringing better efficiency, cost-effectiveness and reliability not previously known. A “drainback” hot water system is the state-of-the-art system design that can be used in any climate and is now the system of choice for most residential and commercial applications.

• DrainBack Systems. State-of-the-art, fail-safe freeze protected with thermal limiting (active, indirect): Collector water is separate from potable water and the collector water drains into a special tank to prevent freezing and overheating concerns, once potable water reaches proper temperature or if no sunlight (heat) is available.
• Glycol Systems: Indirect Heating, Differential or Photovoltaic (PV) Controlled Antifreeze Protection (active, indirect): Collector water is separate from potable water and contains non-toxic propylene glycol antifreeze. This is sometimes referred to as a “pressurized glycol” system and is freeze tolerant. The small electric circulation pump can be powered by a small PV collector.
• Active Direct Systems: Direct Heating, Differential or PV Controlled (active, direct): Potable water is circulated from the storage tank to the collector when heat is available. No additional heat exchanger is required as the collector serves this purpose. The small electric circulation pump can be powered by a small PV collector. This system is for tropical, non-freezing climates.
• Integrated Collector Storage “ICS” (passive, direct): Potable water is both pre-heated and stored in a roof-top unit before going into a conventional water heater. This basic system uses regular “street” or well water pressure to circulate water and does not require pumps or temperature controllers, but is subject to freeze damage.
• Thermo-siphon (passive, direct): Potable water is naturally circulated from the collector to the storage tank positioned above the collector(s). Based on the principle that hot water rises, these self-contained systems heat water without use of pumps or controllers, but are subject to freeze damage. These are typically used in tropical and/or developing countries.

Each of the above systems has their own benefits, limitations and aesthetic considerations. There are many factors that go into selecting a system that meets your needs. As we can have cloudy days and/or high-demand times for hot water, our systems include back-up heating (using electric or gas) to ensure you are never without hot water. Having a solarenergy.com dealer perform a professional site survey is your first step in having a properly sized and installed solar hot water system. Because there are different types of systems and each system requires proper sizing (based on total usage, peak demand and part of the country), it is a critical task to ensure its performance and durability.