This paper presents long-term test data obtained from field tests of electric resistance water-heating systems at 12 single-family detached residences. Hot water usage and inlet water temperatures from these 12 residences were previously reported in 1995 with data from an additional 20 commercial sites, two apartment building laundries, and one other residence. Refer to the ASHRAE symposium paper titled "Effect of Seasonal Changes in Usage Patterns and Cold Inlet Water Temperature on Water-Heating Loads" (Abrams and Shedd 1996.) Measured electric energy usage data and water-heating efficiency data for electric resistance operation are presented here. The test program consisted of a repeated cycle of one week of resistance operation and three weeks of heat pump water heater operation from late 1994 through late 1995.

Test data are available at measurement intervals of one minute for a period of at least one year. Summary data in tabular and graphical form are presented for average daily electric energy usage and delivered water-heating efficiency. Regression equations are provided to relate overall daily water-heating efficiency to average daily hot water usage. Plots of electric energy usage at one-minute intervals are provided for the summer and winter days of maximum energy usage for one site. Conclusions are offered regarding measured performance and efficiency in the field vs. rated values. Analyses and observations are provided on the effect of daily hot water usage on delivered water-heating efficiency and the distribution of energy usage between upper and lower heating elements.

Units: Dual