High-efficiency endless water heaters are also known as tankless hot water, on-demand water heaters, or instantaneous water heaters. They heat water only as it is needed, without a storage tank. This is so they don’t lose heat through the tank's walls and never run out of hot water. Typically, these water heaters provide hot water at a rate of 2 to 5 gallons per minute. In addition to energy savings, other benefits include small size and longer life expectancy.