There are many options available for householders looking to replace their water heater, including solar, storage tank water heaters and electric water heaters.

Solar

These hot water heaters are the greenest option available, as they are fully powered by solar energy. These are suitable for those who are able to make the initial outlay for the solar panels and who live in relatively sunny areas.

Gas condensing

Gas condensing systems are another relatively green option for water heating. These reuse the gas for heating the water.

Storage tank

These are very common in residential properties, and they tend to be inexpensive. The larger the storage tank, the more hot water available on hand.

Electric heat water pump

This type of water heater is often known as a hybrid system, as they use evaporation and compression to produce ambient heat for increasing the water temperature. These tend to be cheaper than the traditional options.

Tankless

Tankless hot water heaters are becoming more popular, as they are instantaneous water heaters that do not expend energy in keeping hot water in a tank. However, tankless systems can be more expensive, and larger homes may need two or more tankless systems for an adequate supply.

Source:http://plumbinghelptoday.com/denver-plumbing-repair-blog/2013/06/pros-and-cons-of-different-types-of-water-heaters/