Residential Load Calculation: NEC 220.83 in Plain English

A residential load calculation estimates how much of your electrical service your home could use at once. For existing homes, the NEC® offers an optional method in section 220.83 (2023 edition): add up the real loads, count the first 8,000 VA in full and the rest at 40%, then compare the result with your main breaker.

Step 1: the general load

Every home gets a baseline for lights and outlets, no matter what's plugged in:

• 3 VA × square footage (living space, not the garage or open porches).¹
• 1,500 VA per small-appliance kitchen circuit, at least two.²
• 1,500 VA for the laundry circuit, at least one.

Step 2: fixed appliances

Add the nameplate rating of each appliance that's fastened in place or on its own circuit: range or cooktop, oven, dryer, water heater, dishwasher, disposal, EV charger, hot tub.³ If you don't know a nameplate, typical values work for a first look — our calculator uses defaults published by city permit offices.⁴

Step 3: the demand factor

Not everything runs at once, so the code discounts the total:⁵

Part	Counts at
First 8,000 VA	100%
Everything above 8,000 VA	40%
New heating or air conditioning (220.83(B))	100%

When you aren't adding heating or cooling, that's method (A). When you are, it's method (B): the heating or cooling stays out of the discount.

Step 4: amps and the verdict

Divide the total by 240 to get amps, then compare with your main breaker size. We call up to 80% green, 80–100% yellow and over 100% red. The worked example below runs the full method on a real-world mix of appliances.

What this calculation is not

It's an estimate based on the numbers you enter, not a design. Your electrician and inspector make the call, and some read existing air conditioning differently under (A). That's why our free check can show a conservative result alongside the standard one.

Technical notes

1. Floor area is calculated from the outside dimensions of the dwelling (NEC® 2023 220.11). Open porches, garages, and unused or unfinished spaces that can't be adapted for future use are left out. Source: NFPA 70 (NEC®), free access. ↩

2. 220.52(A) assigns 1,500 VA to each 2-wire small-appliance branch circuit required by 210.11(C)(1); 220.52(B) does the same for the laundry circuit required by 210.11(C)(2). Extra circuits beyond the minimum add 1,500 VA each. Source: NFPA 70 (NEC®), free access. ↩

3. Two appliances have floors: an electric clothes dryer counts at no less than 5,000 VA or its nameplate, whichever is larger (220.54), and EV supply equipment at no less than 7,200 VA or its nameplate (220.57, added in the 2023 edition). Sources: NFPA 70 (NEC®), free access; dryer default in the City of Newark worksheet. ↩

4. Examples of municipal load-calculation worksheets with default appliance values: City of Morgan Hill; City of Novato; City of Newark. ↩

5. The 40% factor applies to the remainder of the combined load, not to each appliance. New dwellings use the optional method in 220.82 instead, where the first 10 kVA counts at 100%. In the 2026 edition this existing-dwelling method moves to 120.83. Berkeley Lab notes that measured peak demand from smart-meter data is a more accurate alternative to demand-factor estimates. Sources: NFPA 70 (NEC®), free access; LBNL technical brief, 2024. ↩