Condensing Water Heater

If your house uses lots of natural gas to power appliances, a condensing water heater might be just right for you. It is a highly energy efficient water heater system that works by recycling unused gas in your home to heat the water.

The fumes of gas are transferred through the coil at the bottom of the tank to heat the water and they use very little energy that is not used somewhere else in the house — for example, for running the oven. The life expectancy of a condensing water heater is around 10-15 years. Keep in mind that this type of water heater also will require regular maintenance and cleaning.
Probably best option for houses that primarily use natural gas for energy