Determinants of electricity use for residential water heating: The hood river conservation project

Abstract Because 85% of the homes in the Pacific Northwest have electric water heaters, water heating is the second most important residential electricity end-use in the region (second to space heating). This paper analyses the determinants of water-heating electricity use, using end-use load data and responses to a detailed home interview. These data are available for 142 homes in Hood River, Oregon. On average, these homes used 5000 kWh/yr for water heating. Almost 60% of the household-to-household variation in electricity use was explained with eight variables in a simple regression model. The number and ages of household members are the strongest determinants of electricity use: use increases by roughly 1000 kWh/yr with each additional household member. Other statistically significant determinants of water-heating electricity use are hot-water temperature, water-heater location, number of showers in the home and house type. Electricity use varies considerably throughout the year (as well as across households). Weekly usage was 50% higher in mid-winter than in summer. About half of this temporal variation is due to changes in outdoor temperatures and half is due to seasonal changes in behavior (i.e. increased use of hot water in winter).