When the optional method is used, a demand factor of ___ is permitted to be applied to the calculated load of a 15-unit multifamily dwelling.

When the optional method is used, a demand factor of ___ is permitted to be applied to the calculated load of a 15-unit multifamily dwelling.

• A. 75%
• B. 43%
• C. 40%
• D. 70%

Answer: (C)

When calculating the load for a multifamily dwelling, the optional method lets you apply a demand factor to the total calculated load to account for diversity of use—not everyone is at full load at the same time. For a 15-unit building, the table for the optional method permits using a 40% demand factor. This means you take the sum of all the connected loads (the calculated load) and multiply it by 0.40 to get the demand load used for the service calculation. The idea is to reflect that, across many units, simultaneous demand is less than the sum of all individual connected loads. For example, a calculated load of 50 kW would become 20 kW under this method. The other percentages are simply the factors for other unit counts; they don’t apply to a 15-unit building.

When calculating the load for a multifamily dwelling, the optional method lets you apply a demand factor to the total calculated load to account for diversity of use—not everyone is at full load at the same time. For a 15-unit building, the table for the optional method permits using a 40% demand factor. This means you take the sum of all the connected loads (the calculated load) and multiply it by 0.40 to get the demand load used for the service calculation. The idea is to reflect that, across many units, simultaneous demand is less than the sum of all individual connected loads. For example, a calculated load of 50 kW would become 20 kW under this method. The other percentages are simply the factors for other unit counts; they don’t apply to a 15-unit building.