Residential Load Calculator
The Article 220 standard method for a single dwelling — enter the house, get the demand load and a suggested service size, with the math shown.
Outside dimensions, habitable space — don't count garage or open porches.
Standard method for a single dwelling per NEC Article 220 Part III (220.42(B) general demand, 220.53 appliances, 220.54 dryer, 220.55 range, 220.60 noncoincident loads). Real service sizing has more moving parts (EV charging, continuous loads, local amendments) — treat this as a design starting point and verify against the current code.
How the standard method works
The code recognizes that nothing in a house runs all at once, so it applies demand factors: general lighting load (3 VA per square foot plus the small-appliance and laundry circuits) takes 100% of the first 3,000 VA and 35% of the rest; ranges use the famous Table 220.55 Column C (a 12 kW range demands only 8 kW); four or more fixed appliances take 75%; and you count the larger of air conditioning or heat, never both — they don't run together.
Planning an EV charger, hot tub, or shop? Those change the picture fast — add their VA into the fixed-appliance line as a rough check, and have the service sized professionally before buying equipment.