Tankless water heaters
Description:
Tankless water heaters are also called “on-demand water heaters”
because they only heat the water when you turn on a faucet. The water
is heated as it flows through the unit instead of heating a large tank
of water. These systems can be combined with a solar thermal to provide
hot water for domestic use as well as for heating your house.

Advantage to user:
“Endless hot water.” Since there is no tank of hot water, you can’t run out.
Savings to pocketbook:
A traditional type of water heater has a tank that keeps the water hot
all the time. As the water in the tank cools, it heats it up again.
Over and over. Even if you don’t use it. The on-demand heater only
heats the water if you’re using it.
Savings to the planet:
Most water heaters use natural gas or electricity. Even though most
on-demand heaters use the same source of energy, they use way less, up
to 70% less depending on your use.