calcs.homes
calcs.homes
Estimate your home's electrical service size using the NEC 220.82 Optional Method — a simplified, widely used calculation for single-family dwellings. This follows US NEC conventions (120/240V split-phase) and isn't applicable to other electrical codes.
Estimate only — have a licensed electrician verify before upgrading or installing service.
General loads (lighting at 3 VA/sq ft, small appliance and laundry circuits, and fixed appliance nameplates) are summed, then the first 10,000 VA counts at 100% and everything above that counts at only 40% — reflecting that a home never runs every circuit at once. Heating or cooling load (whichever is larger) is added at full value. Total VA divided by 240V gives amps, which we round up to a standard service size (100A, 150A, 200A, or 400A).
It follows the NEC 220.82 Optional Method, a real and commonly used calculation, but only a licensed electrician pulling a permit can perform an official load calculation for your specific home and local amendments.
Many electricians recommend 200A even when 100A meets code minimum, since it leaves headroom for a future EV charger, hot tub, or additional AC — upsizing during a planned upgrade is far cheaper than doing it again later.