These water heaters don’t have a tank, just like the name suggests. Instead, these are compact devices that provide hot water on demand. So instead of collecting water in a tank, heating, and storing it, they quickly heat up water moments before it runs from the faucet. These appliances allow you to save space in your home, and they can also significantly reduce your energy bills. Plus, they are much easier to maintain than tank heaters, and they last about twice as long. Finally, tankless units provide an unlimited supply of water, so you don’t need to worry about running out before everyone has had a chance to take a shower. At the same time, they cost significantly more than regular units. Tankless units can be powered by gas or electricity.