Under the optional method for a single-family dwelling, general loads beyond the initial 10 kW are calculated at a ___ percent demand factor.

Under the optional method for a single-family dwelling, general loads beyond the initial 10 kW are calculated at a ___ percent demand factor.

• A. 40
• B. 50
• C. 60
• D. 75

Answer: (A)

The concept here is load diversity in the optional dwelling unit method. In this approach, you don’t treat every watt as if it could occur at the same moment. Instead, you base the calculation on a base amount plus a reduced factor for the additional loads. The first 10 kW of general lighting and receptacle loads is used at full value as the base. Any general loads beyond that initial 10 kW are multiplied by 0.40 (40%) to reflect that these loads are unlikely to be at their maximum simultaneously with the base load. This reduces the total calculated demand and helps size the service more realistically. For example, if there are 12 kW of general loads, you’d count the first 10 kW at 10 kW, and the remaining 2 kW at 40% (0.8 kW), giving a total of 10.8 kW. This illustrates how the 40% factor lowers the contribution of additional loads. So the correct factor for general loads beyond the initial 10 kW is 40%.

The concept here is load diversity in the optional dwelling unit method. In this approach, you don’t treat every watt as if it could occur at the same moment. Instead, you base the calculation on a base amount plus a reduced factor for the additional loads.

The first 10 kW of general lighting and receptacle loads is used at full value as the base. Any general loads beyond that initial 10 kW are multiplied by 0.40 (40%) to reflect that these loads are unlikely to be at their maximum simultaneously with the base load. This reduces the total calculated demand and helps size the service more realistically.

For example, if there are 12 kW of general loads, you’d count the first 10 kW at 10 kW, and the remaining 2 kW at 40% (0.8 kW), giving a total of 10.8 kW. This illustrates how the 40% factor lowers the contribution of additional loads.

So the correct factor for general loads beyond the initial 10 kW is 40%.