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using HWSIM or a similar tool. For centralized DHW systems, a detailed analysis is required to estimate distribution losses and pump energy.

For all distribution systems, the heat gain, recovery load, and pump energy shall be applied using the combined hourly DHW profile in Figure 14. The change in hot water use shall be applied in accordance with the corresponding end-use DHW profile. The BA Analysis Spreadsheet automates these calculations based on the distribution system characteristics entered for the Prototype.

If the builder does not provide a clothes washer in the Prototype house, housing unit, or a common laundry room, the Prototype shall be modeled with the Benchmark clothes washer and dryer in the appropriate location.

The optional DHW event characteristics for the Benchmark (see Table 12) may be modified if the Prototype includes low-flow fixtures, an alternative distribution system, or energy efficient appliances. The DHW Event Generation Tool must be used to create the event schedules for the Prototype if the Standard DHW Event Schedules are not used.

The installation of energy-saving appliances or other equipment may reduce hot water consumption for certain end uses, reduce the internal sensible and latent loads, or affect the hourly operating profiles. Energy savings calculations for the Prototype must take these effects into account using operating conditions based on rules developed for DOE residential appliance standards (DOE 2003), and the actual performance characteristics of the appliances. The number of cycles per year specified in the appliance standard for clothes washers is adjusted according to the number of bedrooms and the clothes washer capacity, using Equation 17:

Equation 17:

Clothes washer cycles per year = (392) × (½+Nbr/6) × 12.5 lb/Wtest


Wtest = maximum clothes washer test load weight found in 10 CFR part 430, Subpt B, Appendix J1, as a function of the washer capacity in ft3. Nbr = number of bedrooms.

A dryer usage factor (DUF) is applied to the clothes washer cycles to determine the number of annual dryer cycles, using Equation 18:

Equation 18: Clothes dryer cycles per year = DUF × Clothes washer cycles per year


DUF = 0.84.

The dishwasher annual operating cycles are similarly calculated, using Equation 19:

Equation 19: Dishwasher cycles per year = (215) × (½ + Nbr/6)

The BA Analysis Spreadsheet posted on the BA Web site automates these calculations, and is strongly recommended for the analysis of water-consuming appliances. The spreadsheet includes equations to help analysts calculate energy savings for efficient clothes washers, clothes dryers, and dishwashers. It calculates the split between hot water and machine energy based on the EnergyGuide label, estimates dryer energy savings for clothes washers that reduce remaining


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