Electrical Load Calculator
NEC-style dwelling unit load calculation → total demand VA, amps, and recommended service size.
NEC standard dwelling method (220 Part III)+
General lighting = Area × 3 VA/ft²
+ 2 small-appliance circuits @ 1500 VA each, + 1 laundry @ 1500 VA
Demand: first 3,000 VA @ 100%, next 117,000 VA @ 35%
+ Fixed appliances (water heater, dryer, range) + HVAC (larger of heat/cool) + EV
Service amps = Total VA / V; size to next standard breaker with 125% continuous-load factor.
Simplified NEC calculation for early sizing. Permit calcs must be sealed by a licensed Electrical Engineer or completed by a licensed electrician on the local jurisdiction's form.
Frequently asked questions
Which NEC method does this use?+
Standard dwelling-unit calculation per NEC Article 220 Part III (220.40-220.55) for residential. For commercial/optional calcs, use Part IV/V and consult a licensed Electrical P.E.
Why 3 VA/ft² for lighting?+
NEC 220.12 Table — 3 VA/ft² is the general lighting and receptacle unit load for dwelling units. Commercial uses 3.5 VA/ft² for office; 2 VA/ft² for warehouse.
How is the demand factor applied?+
First 10 kVA of lighting + small-appliance + laundry counts at 100%; remainder at 35% per NEC Table 220.42. Largest motor adds 25%. HVAC counts at 100% of larger of heat or AC.
What service size should I install?+
Round UP to the next standard size: 100, 125, 150, 200, 320, 400 A. A 200 A service is the modern residential default; EV charging and heat pumps may push to 320 A.
Is this load calculation acceptable for permit?+
Permit calcs must be sealed by a licensed Electrical Engineer or completed by a licensed electrician on a jurisdiction-approved form. Use this tool to pre-size before paying for design.
What does 'demand load' mean?+
The realistic peak draw, not the nameplate sum. NEC applies demand factors because not all appliances run simultaneously at full power.