Dwelling Electrical Load Calculator

What Is It

Dwelling load calculations determine the minimum electrical service size (amperage) a home needs by summing general lighting load, small appliance and laundry circuits, fixed appliances, and heating/cooling load, then applying a demand factor that recognizes not everything runs at once.

How to Calculate

Enter the home's square footage, number of small-appliance circuits (minimum 2 required), whether there's a dedicated laundry circuit, any other fixed appliance loads, and the larger of the heating or air conditioning load. The calculator sums the general loads, applies the demand factor (100% of the first 10,000 VA, 40% of the remainder), adds the HVAC load at 100%, and recommends a standard service size.

Example

An 1,800 sq ft home with 2 small-appliance circuits and a laundry circuit: general load = (1,800x3) + (2x1,500) + 1,500 = 10,500 VA. Demand load = 10,000 + (500x0.4) = 10,200 VA. Adding an 8,000 VA A/C load gives 18,200 VA total, about 76A at 240V - comfortably served by a standard 100A service.

Recommendations

This optional method applies to a single dwelling unit with a 100A or larger service; larger or multi-family loads typically require the more detailed standard method. Always leave margin for future additions like an EV charger or a heat pump conversion.

Frequently Asked Questions