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In temperate climates the sun may be seasonal.
Typically, solar systems depend on temperature sensors, valves, electronic switches, antifreeze, and/or heat exchangers to keep pipes from freezing in the winter. However, the most practical solar hot water heaters are often the simplest.
In some climates, a solar thermal system can provide all the hot water a hybrid household needs, for both domestic use and space heating. A radiant heating system circulates warm water (about 100 degrees Fahrenheit) through durable polyethylene (PEX) tubing encased in concrete floors or thick plaster. As it is pumped through the system, the warm water radiates its heat into the mass surrounding it. When the sun is shining, a solar system can furnish this heat, backed up by a conventional or on-demand hot water heater.