What are tankless water heaters? Why has it become such a huge hit to homeowners? These water heaters are also known as demand-type or instantaneous. Hot water comes out only when you need it. This makes them energy-efficient as they don’t use up standby energy. These may not be the best option if you don't want to spend much when it comes to your water heating equipment. But in the long run, you save more money.   Consider this article as a 101 on tankless water heaters. Below are a few facts that will help you with your buying decision.