Electric Tankless Water Heaters Save energy and reduce your electric bill: Regular gas water tank heaters are subject to stand-by losses which amount to 15 - 20% of the kWH used. In addition, water in a tank has to be heated hotter than necessary to account for these stand-by losses. Changing to a tankless system eliminates these problems and results in typical savings of at least 15 - 20% on the heating portion of your electric bill.