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Conversion of sunlight to heat is one of the most efficient, cost-effective and widely applicable means of generating renewable energy. There are many methods, technologies and brands form which to choose. However, in the Eastern Ontario climate, all systems that operate year-round must be freeze protected.
Leading types of solar water heating systems use:
- Flat Plate (or Glazed) collectors – flat panels with glass and a flat, black metal plate with circulating fluid to capture and transfer heat
- Evacuated Tube collectors – large evacuated tubes, like Thermos bottles, with metal plates inside and a means to transfer captured heat. The vacuum acts as an insulator to prevent losses
- Unglazed collectors – large polymer panels typically used to heat pool water directly. These systems do not have freeze protection and must be drained seasonally.
 Both flat plate and evacuated tube systems can be used in domestic and industrial applications. Flat plate systems are typically less expensive but are outperformed by evacuated tubes in cold weather conditions. A well sized flat plate system should displace 50% or more of the annual energy needed to heat water, while evacuated tubes should displace about 70%. There is no universal rule concerning which system is best: only knowledgeable understanding of the physical properties of each system, and careful consideration of your unique circumstances, can yield the appropriate recommendation.
 Typically solar water heating systems are expected to last over 25 years with good maintenance. Even at today’s prices, they are generally cost-competitive or better than fossil fuels. As fuel prices rise the economics shift increasingly in their favour. A good rule of thumb is that the greater the water heating energy demand, the larger and more economical the solar water heating system.
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