Solar Heater A solar heater is a device that uses heat from the sun (solar energy) to heat a substance; as can be water; oil; brine; glycol or air. Its most common use is to heat water for use in swimming pools or health services (showers, laundry or dishes etc.) both domestic environments such as hotels and other industries. In many climates, a solar water heater can reduce energy consumption used to heat water. This decrease can be of up to 50% - 75% or even 100% when fully replaced; eliminating the consumption of gas or electricity. Although many developing countries have very favorable climate for the use of these systems; their use is not widespread due to the initial cost of installation. In several developed countries, state regulations require the use of these systems in new housing. The heaters have a high efficiency to capture solar energy. Depending on the implemented technology and materials; they can reach efficiencies of 98%. Not to be confused with the thermal solar panel photovoltaic panel; which is not used for heating substances; but to generate electricity from light .