Electrical Load Calculator

The NEC standard method adds general lighting (3 VA per square foot), small-appliance circuits, and laundry circuits, then applies a demand factor — the first 3,000 VA at 100% and the remainder at 35%. Fixed appliances like the range, water heater, dryer, and AC are added on top. Dividing the total VA by 240 volts gives the calculated load in amps.

This calculator returns the smallest standard service — 100, 125, 150, 200, 225, 320, or 400 amps — that is at least as large as the calculated load. Most modern single-family homes land on a 200 A service, but the right answer depends on your square footage and appliances. A licensed electrician must confirm before any upgrade.

For resistive loads like heaters, ranges, and water heaters, watts and volt-amps are effectively the same. The standard method in NEC Article 220 works in VA, so entering nameplate watts gives a close estimate. Motor-heavy loads have a power factor that makes VA slightly higher, which is one reason this is an estimate and not a stamped calculation.

No. The NEC lets you count only the larger of the heating load or the air-conditioning load, since they rarely run at once. This simplified calculator adds every appliance you enter, so if you list both electric heat and AC the result will be conservative. Enter only the larger of the two if you want to match the code rule.

The standard method in 220.42 through 220.55 applies separate demand factors to lighting, appliances, ranges, and dryers. The optional method in 220.82 lumps most loads together at 100% for the first 10 kVA and 40% above that. They can produce different service sizes. This tool uses a simplified version of the standard method only.

Yes. A Level 2 EV charger is a continuous fixed load and can add 7,200 to 11,500 VA, which is often what pushes a home from a 100 A or 150 A service to 200 A. Add it as an appliance row with its nameplate rating to see the effect on the recommended service.

No. This is a planning estimate to help you scope and quote work. Permits and service upgrades require a full load calculation, often stamped, performed by a licensed electrician using the complete NEC rules, including the larger-of-two rule and the largest-motor adder. Always have a professional verify before filing.

Yes, the calculator is completely free with no signup required. Your inputs, including the appliance list, are saved locally in your browser so they persist between visits — nothing is uploaded to a server. Clearing your browser data will erase your saved values.