An evacuated tube solar water heater is a type of solar thermal system that uses a series of evacuated tubes to absorb solar energy and convert it into heat. Evacuated tubes are made of two layers of glass, with a vacuum in between, which helps to insulate the tubes and increase their ability to absorb solar energy. The heat is then transferred to water or a fluid that is circulated through the evacuated tubes and stored in an insulated storage tank. Evacuated tube solar water heaters are often used in areas with colder climates or low solar radiation, as they are more efficient in these conditions than flat plate solar water heaters. They are also more durable and can withstand high winds and heavy snowfall. Evacuated tube solar water heaters can be used in both active and passive systems, similar to flat plate solar water heaters.