Electrical Use, Efficiency, And Peak Demand Of Electric Resistance, Heat Pump, Desuperheater, And Solar Hot Water Systems

Secondary Author(s)

Parker, Danny

Report Number





Water Heating; Buildings; Energy Efficiency; Solar Thermal


Eighty single family residences in Florida were monitored for two years in order to collect data on water heating electrical energy consumption, efficiency, and time-of-day demand. The homes were divided into equally sized samples of four different water heating systems: conventional electric resistance, heat pump, desuperheater and solar hot water systems. Electrical consumption for electric resistance water heaters averaged 8.3 kWh per day in Florida with an average water heating system efficiency of 82%. Desuperheaters used an annual average of 7.4 kWh per day at an annual system efficiency of 110% and heat pump water heaters used 6.1 kWh per day at an average system efficiency of 153%. Electrical use of solar hot water systems averaged 2.7 kWh per day and the average system efficiency was 235%. Electrical demand taken at 15-minute intervals showed electric resistance water heaters contribute approximately 1.1 kW of diversified demand to the utility winter peak and at least 0.2 kW to the summer peak. Solar hot water systems exhibited the most desirable demand profile relative to Florida utility coincident peak loads with a 0.7 kW per customer reduction in the winter and a minimum 0.2 kW per customer reduction in the summer. Desuperheaters have the same 0.2 kW minimum peak demand reduction in the summer and 0.2 kW per customer reduction in the winter. Heat pump water heaters exhibited approximately half the peak demands of electric water heaters in the winter but were unable to reduce summer peak demand by any significant amount. Installation of solar hot water collector.Since electric water heaters account for approximately 25 percent of the utility winter peak demand per customer, encouraging the use of alternative water heating methods is beneficial to a winter-peaking utility in Florida.

Date Published



Buildings - Energy Efficiency; Solar Thermal; Water Heating

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