Electrical Load Calculator — NEC 220.82
Residential service sizing for a single dwelling unit using the NEC 2023 optional method: general load with the 10 kVA / 40 % demand factor, plus the largest heating or cooling load. Outputs calculated amps, standard service size and service-entrance conductor.
Under 80 % utilization leaves headroom for future loads. Check your AHJ and utility — some require the standard method (220 Part III) or a minimum 200 A service.
BasisNEC 2023 220.82 optional method · 3 VA/ft² · first 10 kVA @ 100 %, rest @ 40 % · largest of 220.82(C) · ÷ 240 V · conductors 310.12 (83 %), 75 °C column
Frequently asked questions
What is the NEC 220.82 optional method?
NEC 220.82 is an optional calculation for a single dwelling unit served by a 120/240 V or 208Y/120 V service of 100 A or more. Instead of applying separate demand factors to lighting, ranges, dryers and appliances (the standard method in Part III of Article 220), it adds up the general loads, takes the first 10 kVA at 100 % and the remainder at 40 %, then adds the largest heating or air-conditioning load at its own demand factor. It usually gives a smaller — and still code-compliant — service size than the standard method.
What counts as general load under 220.82(B)?
Three volt-amperes per square foot of floor area (outside dimensions, excluding open porches, garages and unfinished spaces not adaptable to future use), 1500 VA for each 20 A small-appliance branch circuit and each laundry circuit, and the nameplate rating of all appliances that are fastened in place, permanently connected, or on a specific circuit — ranges, ovens, cooktops, dryers, water heaters, dishwashers, disposals, EV chargers and similar.
How are heating and air conditioning handled?
220.82(C) lists several options and you include only the largest: 100 % of air-conditioning, 100 % of a heat pump without supplemental heat, 100 % of the heat-pump compressor plus 65 % of supplemental electric heat, 65 % of central electric space heating or of fewer than four separately controlled heating units, or 40 % of four or more separately controlled units. Because heating and cooling do not run at the same time, only the larger is counted.
How is the service size chosen?
The calculated load in VA is divided by 240 V to get amperes, then rounded up to the next standard service rating. A one-family dwelling service must be at least 100 A (230.79(C)). The service-entrance conductors may be sized at 83 % of the service rating per 310.12 for 120/240 V dwelling services up to 400 A, using the 75 °C column of Table 310.16.
How should an EV charger be entered?
Enter the EVSE nameplate rating. NEC 220.57 sets the EVSE load at 7200 W or the nameplate rating, whichever is larger — a 40 A circuit with a 32 A charger at 240 V is 7680 VA. Under 220.82 it is part of the general load, so it is taken at 40 % once the first 10 kVA is used up.