There are two major types of water heaters: traditional storage tanks that hold 20 to 80 gallons of water and tankless heaters, which heat water as it passes through the unit. Each type comes with variations that can be used with gas, propane or electricity. You can also buy solar water heaters, with an electric or gas backup. Most people buy the water heater from the plumber who installs it, though you can buy your own from a hardware store. Discuss options with your plumber and tell him or her about your needs: more hot water, energy savings or other considerations, plus ask for recommendations. There ae lots of things to consider when buying a new water heater. For an expert’s advice, read the full story on our sister site, Living on the Cheap.