If you do not know how your water is heated, check your energy utility bill, or contact your energy provider or your landlord to determine if natural gas or electricity is used. You may also select the "don't know" option. However, if this is selected, the calculator will not be able to provide an estimate of the energy savings expected from the installation of WaterSense labeled faucets, or the retrofit of old faucets with WaterSense labeled aerators.