ELECTRIC HEAT PUMP
This is a heat pump water heater that uses the temperature of your home to help heat the water. So instead of using energy to go from 40-50 degrees F it is from 70-75 degrees F savings lots of energy, money, and fossil fuels.
Heat pumps for your home work in a similar way and the newest one are tested and approved for working down to -17F!
Not to mention how good it is to use with solar. Use the sun to heat your home!