solar thermal collector collects heat by absorbing sunlight. The term "solar collector" commonly refers to a device for solar hot water heating, but may refer to large power generating installations such as solar parabolic troughs and solar towers or non water heating devices such as solar air heaters Solar water heaters use natural sun light to heat water. This system works on the thermosiphon principle and is designed to provide hot water without consuming expensive electricity. This is the most effective way to generate hot water thereby saving costly power and is also environment friendly