Although clothes washers consume energy for both mechanical activities and water heating energy, the majority of the energy used is for water heating. Both machine energy and water heating energy are directly dependent upon the number of loads washed. To estimate the energy consumption of these appliances, Equations 12 and 13 use the calculation method described in the Energy Data Sourcebook (Wenzel et al. 1997). Equation 14 calculates the water heating portion of the total clothes washer energy.
EC = ME + WE Equation 12
EC = Annual energy consumption in utility units
ME = Machine energy (kWh/year)
WE = Water heating energy attributable to clothes washer in utility units (returned from water heater module)
When ME and WE are in different units (e.g. for non-electric water heaters) the energy consumption for the clothes washer is calculated and stored separately for both fuels (e.g. 126 kWh and 23 therms).