The calculation of annual energy consumption by appliances and miscellaneous enduses utilizes the following equation:

Annual consumption = Rated Power (Watts) * Hrs/day of usage * 365 days / yr.

The first step is to identify the appropriate unit energy consumption (UEC) for the technology in question. Large appliances, such as refrigerators, can have very different energy consumption depending on the year of manufacture, and features which affect energy use, like automatic defrost or side-by-side design. To estimate the energy consumption of these appliances, we utilized shipment weighted energy consumptions (See Table 1 & Table 2 below). This number is the average consumption for all units sold within a particular year weighted by the number of units in each consumption bin. This information was provided by AHAM, the Association of Home Appliance Manufacturers [1]. User inputs provide information about the appliance type and year. They are used in selecting energy consumption. For smaller appliances, and miscellaneous end-uses, a generalized annual UEC was used. This number is an estimate of the total energy consumed in a year, based on power draw and assumptions about typical usage. The specific assumptions pertaining to small appliances are based on the synthesis of many years of research here at Lawrence Berkeley National Laboratory [2].

In situations where differing usage for an end-use results in large changes in energy consumption, consumers are encouraged to enter their indvidual hours of usage, which go into calculating the energy consumed. To hasten the inputting process, assumptions about usage were used for the majority of smaller end-uses (See Table 3).

Finally, default selections were set up to reduce the amount of input necessary to complete the module. Enduses having a saturation of 86% or greater in the overall housing stock are selected on the web page when it first loads [2].

Maggie Pinckard
Research Associate, LBNL

[1] AHAM, Energy Efficiency and Consumption Trends, var. products. July 1996.

[2] Sanchez, Marla C., Miscellaneous Electricity Use in U.S. Residences. MS Thesis, University of California, Berkeley. June 1997.