Today’s cutting edge hot water technology is heat pump water heaters which are 3-5 times more efficient than electric resistance hot water systems (HWS). While heat pump HWS are more expensive to purchase, their high efficiency makes them cheaper in the long run. Resistance systems (cylinders) are cheaper to buy and easier to install and are also a clean tech solution if, like heat pumps, they are renewably powered. Solar hot water (solar thermal) which comes in many forms, including evacuated tubes, provide another cheap and easy to install third option.