Freezer Energy Consumption

Freezer energy consumption is driven by many factors such as configuration (e.g. upright freezers versus chest freezers) and technology (automatic vs. manual defrost capability). Additionally, over the years, freezers have increased in size, causing the overall energy consumption to increase. To estimate the energy consumption of these appliances, we use the calculation method described in the Energy Data Sourcebook (Wenzel et al. 1997).

Because most consumers do not know the Energy Factor of their freezer(s), we use a shipment-weighted energy factor based on the year the freezer was purchased (Table 16). This number is the average energy factor for all units sold within a particular year weighted by the number of units in each efficiency bin (AHAM 1996). Note that for purposes of this model, all freezers are assumed to be stand-alone units (no fresh food compartment).

Equation 10

where

EC = Annual energy consumption (kWh/year)

AV = Adjusted volume (cubic feet)

EF = Energy Factor (cubic feet•day/kWh)

The adjusted volume is intended to capture in a single parameter the relatively high energy intensity of the freezer’s frozen food compartments. Equation 11 is used to calculate adjusted volume (US DOE 1995). This definition corresponds to the volume used in defining federal minimum efficiency standards

Equation 11

where

AV = Adjusted volume (cubic feet)

Size = "Nominal" freezer volume (cubic feet)

Note that this model does not account for freezer usage factors that might vary between units, such as temperature settings, door opening frequency, food loading rates, and ambient temperatures. While these factors can have a large impact on energy consumption, their effect has not been quantified in a way that could be incorporated into a parametric model such as this.