On-demand water heaters place demands on electrical system
A steady stream of seemingly endless hot water is one goal of tankless water heaters, but the PUD does not recommend electric tankless heaters.
Since about 20 percent of a home’s energy costs are the result of heating hot water, many customers contact Chelan PUD about alternatives to the standard water tank. One popular option considered by these consumers is the on-demand water heater, also known as “tankless” or “instantaneous.”
Traditional storage water heaters keep water hot at all times, even when it’s not being used, which produces standby energy losses. In other words, you’re spending money to keep water hot even when you don’t need it. On-demand water heaters provide hot water only as it is needed.
Sounds like a good idea, but the PUD does not recommend electric on-demand water heaters. “The reason for this is the high electric demand these units require,” said Mark Wiser, residential program manager. “An electric on-demand water heater large enough for a family of four will require approximately 20 kilowatts (20,000 watts) of power to operate. This compares to 4 kilowatts for an electric water heater with a storage tank or 13 to 16 kilowatts for an electric furnace or air-source heat pump.”
Customers might need to upgrade their service panel to handle the extra load. Plus the units themselves are expensive, Wiser said, costing two to three times more than a storage tank water heater.
On the other hand, Wiser noted, gas and propane on-demand water heaters work very well, don’t have a big electrical demand, and are eligible for a federal tax credit.
Related article
Demand water heaters (Department of Energy Web site)
