Which device converts sunlight into heat for hot water without first producing electricity?

A solar thermal collector converts sunlight into heat for hot water without first producing electricity.

Collectors absorb solar radiation and transfer the resulting heat to a circulating fluid, usually water or a water-based mixture. In domestic systems, that heat can warm water in a storage tank. Common designs include flat-plate collectors and evacuated-tube collectors.

This technology differs fundamentally from a photovoltaic module. Photovoltaic panels convert light directly into electrical energy through semiconductor materials, whereas solar thermal systems capture heat. A home can use both technologies: solar thermal collectors for hot water and photovoltaic panels for appliances, lighting, or battery charging.

Solar thermal collectors are especially useful where hot-water demand is regular and sunlight is sufficient. They can reduce the energy required from gas, electricity, or other backup systems, although most installations still need auxiliary heating for cloudy periods or unusually high demand.