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WattSimple

Home Electrical Load Calculator

Estimate your home's electrical demand using the NEC load-calculation method — with the demand factors that naive 'add up the watts' tools miss — and see whether your 100A or 200A service has room for a new load like an EV charger or heat pump.

Service size
W
W
W
W
A

Within capacity

167 A / 200 A

84% of service used (calculated demand)

General lighting + small-appliance (demand)
5,625 VA
Electric range
8,000 VA
Electric dryer
5,000 VA
Water heater + fixed appliances
6,000 VA
Heating / cooling (larger of)
3,500 VA
EV charger (125% continuous)
12,000 VA

NEC Article 220 standard method with demand factors — an estimate, not a stamped load calc. The EV charger counts at 125% (continuous). A licensed electrician and your local AHJ make the final call; service upgrades also need utility coordination.

Frequently asked questions

It's decided by a load calculation, not by counting breaker slots. The NEC (Article 220) totals your demand — general lighting, appliances, the larger of heating or cooling, and continuous loads like an EV charger at 125% — applying demand factors because everything rarely runs at once. If the calculated demand stays comfortably under your service rating, you have room.

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