Appliances and Miscellaneous Electric Loads
As with lighting, several characteristics must be defined for appliances and miscellaneous electric loads (MELs): the amount of the load, the schedule of the load, the location of the load, the fraction of the load that becomes a sensible load, and the fraction of the load that becomes a latent load. Though the internal load may be treated as an aggregate, the energy consumption for each end use must be considered separately. A breakdown of annual energy consumption and associated internal loads for major appliances and other equipment is shown in Table 23 (Jiang et al. 2008 and Sachs 2005 for multi-family). It is assumed for modeling purposes that all major appliances are present in both the Benchmark and the Prototype, even in cases where the builder does not provide all appliances, except the clothes washer in cases where the Prototype is a housing unit in a multi-family building with a common laundry room. Not all of the energy consumed by appliances is converted into internal load; much of the waste heat is exhausted to the outside or released down the drain in the form of hot water. The appliance loads were derived by NREL from EnergyGuide labels, a Navigant analysis of typical models available on the market that met 1990s National Appliance Energy Conservation Act appliance standards, and several other studies.
For a house of typical size (1000–3000 ft2), the loads from the occupants and most appliances are assumed to be a function of the number of bedrooms and the finished floor area. The exceptions are the refrigerator and certain miscellaneous gas and electric loads, which are assumed to be constant regardless of the number of bedrooms. The general relationship between appliance loads, number of bedrooms, and house size, was derived empirically from the 2001 RECS. The sensible and latent load fractions were developed based on engineering analysis and judgment.
The MEL end use is assumed to be primarily a function of finished floor area and number of bedrooms. A multiplier is applied if the prototype is located in one of the four most populated states as determined in the EIA RECS (DOE 2001). Multipliers for these four states were estimated based on the final electric end-use regression equations developed for the 2001 RECS, substituting national average values for known housing characteristics and physical traits of the occupants (such as number of bedrooms, number of ceiling fans, and age of homeowner) and removing end uses that are disaggregated in the Benchmark (such as lighting and clothes dryer). The resulting multipliers are listed in Table 24. The multiplier is 1.0 for all states not listed because insufficient information is available about the magnitude of MELs in those states.
MELs are broken into variable electric loads and fixed gas and electric loads. By definition, energy savings are not calculated for improvements to fixed loads because an analysis methodology has not yet been established. However, NREL has developed a methodology for calculating energy savings associated with variable electric loads, which are generally the most common MELs encountered in a typical house. Approximately 100 MELs in this category are listed in Table 25. If the analyst chooses to use anything other than the Benchmark MEL values for the Prototype, he or she must use the BA Analysis Spreadsheet for new construction posted on the BA Web site (http://www1.eere.energy.gov/buildings/building_america/ perf_analysis.html) to calculate energy savings, latent and sensible loads, and the split between standby and operating energy. This spreadsheet allows the analyst to change the quantity of each MEL in the Prototype, and the operating and standby power levels only. Operating hours cannot be changed, but a lower “effective” power draw may be used if occupancy sensors or other controls are used to turn off power to MELs that are not in use. In addition, only those MELs that are installed or provided by the builder may be included in the energy savings analysis. The