Instantaneous demand hot water heaters use natural gas, propane, or electricity and so it is not a renewable energy technology. On the other hand, it is a very energy-efficient method of producing domestic hot water and a key backup component to a reliable renewable energy system in your home.

Instantaneous demand water heaters produce hot water instantly when you turn on a hot water faucet. But unlike conventional domestic hot water heaters, hot water is not stored in a tank. This 'tankless' design eliminates stand-by heat loss from the storage tank during the times when you are not using hot water. The elimination of stand-by heat loss results in considerable energy savings.

'Tankless' instantaneous demand water heaters are an ideal backup domestic hot water system for most renewable energy designs, ensuring a reliable supply of hot water during times of high demand, such as when you have guests staying over.