NEC Residential Load Calculator
Size a US dwelling service using the NEC Article 220.82 optional calculation. Enter floor area, fixed appliances and heating/AC to get the minimum service size — with every step and the cited rule shown.
This tool estimates calculated load for guidance only. Final design must be verified by a licensed electrician and approved by the local authority having jurisdiction. State, provincial and local amendments may differ.
This tool estimates calculated load per CEC Rule 8-200 for guidance only. Final design must be verified by a licensed electrician and approved by the local AHJ. Provincial amendments may differ.
Dwelling (NEC 220.82)
Sum the nameplate VA of the range, oven, dryer, water heater, dishwasher and other fastened-in-place appliances.
Minimum service size
100 A
- Calculated load
- 23,680 VA
- Calculated current
- 98.7 A
- General loads (demand)
- 18,680 VA
- Heating / A/C (largest)
- 5,000 VA
- This tool estimates a dwelling-unit load per NEC Article 220.82 (optional method) for guidance only. Final design must be verified by a licensed electrician and approved by the local AHJ. State and local amendments may differ.
- Based on NEC 2023 (NFPA 70), Article 220.82, United States (NEC base).
How this is calculated
General connected load — 220.82(B)
3 VA/ft² × area + 1500 VA × small-appliance circuits + 1500 VA × laundry + fixed appliances
= 3 × 1,500 + 1500 × 2 + 1,500 + 22,700
31,700 VA
General demand — first 10 kVA at 100%, remainder at 40%
100% × first 10000 VA + 40% × remainder
= 10,000 + 40% × 21,700
18,680 VA
Heating / A/C — 220.82(C) largest selection
max(A/C at 100%, space heating at its demand factor)
= A/C 5,000 VA vs heating 0 VA
5,000 VA
Total → current → service size
(general demand + heating/AC) ÷ 240 V, then next standard size
= 23,680 ÷ 240 = 98.7 A → {100, 125, 150, 200, 225, 300, 400}
100 A service
How to do an NEC 220.82 load calculation for a dwelling
The NEC Article 220.82 optional method totals the general loads, applies a two-tier demand factor, then adds the largest heating or cooling load. Take a 2,000 ft² home with a 12 kW range, a 4.5 kW water heater, a 5 kW dryer and a 3.5 kW air conditioner. General loads: 3 VA/ft² × 2,000 = 6,000 VA, plus two small-appliance circuits and one laundry circuit at 1,500 VA each (4,500 VA), plus the appliance nameplates (21,500 VA) — 32,000 VA connected. Demand: 100% of the first 10 kVA plus 40% of the remaining 22,000 VA = 18,800 VA. Add the A/C at 100% (3,500 VA) for 22,300 VA ÷ 240 V ≈ 93 A, which rounds up to the NEC minimum 100 A service.
The 100% / 40% demand and 220.82(C) heating vs cooling
General loads (lighting at 3 VA/ft², the 1,500 VA small-appliance and laundry circuits, and every fixed-appliance nameplate) take 100% of the first 10 kVA and 40% of everything above it — the diversity credit that makes the optional method smaller than the standard method for most homes. Heating and air-conditioning are handled separately under 220.82(C): the calculation uses the largest applicable option — A/C at 100%, a heat-pump compressor at 100% plus supplemental heat at 65% (220.82(C)(2)), or electric space heating at 65% (40% with four or more separately controlled units) — rather than adding heat and A/C together.
Determining floor area — 220.82(B)(1)
Measure from the outside dimensions of the dwelling. Count all habitable floors. Do not count open porches, garages, or unused or unfinished spaces not adaptable for future use. Getting the area right matters less here than under the CEC — at 3 VA/ft² and a 40% marginal demand factor, 100 ft² moves the result by only 120 VA.
Standard service / panel sizes
| Service size | Typical use |
|---|---|
| 100 A | Code minimum — most gas-heated single dwellings |
| 125 A | Dwellings with A/C, EV charging or modest electric heat |
| 150 A | Larger homes with several heavy appliances |
| 200 A | All-electric homes, electric heat plus EV charging |
| 400 A | Large all-electric homes or multiple heavy loads |
How an EV charger changes your load
EV supply equipment enters the calculation at its nameplate — a 48 A/240 V charger is 11,520 VA. As a general load it still gets the 40% marginal demand credit above 10 kVA, but it routinely pushes a 100 A service past its limit. A load-management system (NEC 625.42) can cap the demand the EVSE adds, often letting an existing service stay compliant — enter the managed value when one is installed.
Common load-calculation mistakes
- •Using the optional method where it does not apply. 220.82 covers a single dwelling served by a 120/240 V or 208Y/120 V service of 100 A or greater — otherwise use the standard method (Part III).
- •Forgetting the small-appliance and laundry circuits. They are 1,500 VA each and mandatory, even for an empty kitchen.
- •Adding heating and A/C together. 220.82(C) uses only the largest of the heating/cooling options.
- •Using a stale code edition or ignoring state and local amendments. Adopted editions differ by jurisdiction.
- •Treating the result as a final design. It is an estimate — a licensed electrician and the AHJ must verify before any work.
Frequently asked questions
What is the NEC optional method for a dwelling load?+
NEC 220.82 lets you total the general loads (3 VA/ft² lighting, 1500 VA per small-appliance and laundry circuit, plus fixed-appliance nameplates), apply 100% to the first 10 kVA and 40% to the remainder, then add the largest applicable heating or air-conditioning load from 220.82(C).
What is the minimum service size for a US dwelling?+
NEC 230.79(C) requires a minimum 100 A service for a one-family dwelling. The calculator rounds the calculated current up to the next standard size (100, 125, 150, 200 A and up).
What size electrical service do I need?+
Take the calculated load in VA, divide by 240 V to get amps, then round up to the next standard size: 100, 125, 150, 200 or 400 A. NEC 230.79(C) sets a 100 A minimum for a one-family dwelling; all-electric homes with heating and EV charging often need 200 A.
Does this replace a licensed electrician?+
No. This is an estimating aid only. The final service design must be calculated and verified by a licensed electrician and approved by the authority having jurisdiction. State and local amendments may change the constants used.
Methodology & sources
Constants for both the CEC Rule 8-200 and the NEC Article 220.82 calculations live in versioned datasets keyed to the code edition, so a code update is a data update, not a logic change. This is an estimating aid only — a licensed electrician must verify the final design and the authority having jurisdiction must approve it.
- CSA C22.1:24 Canadian Electrical Code, Part I (26th edition) — Rule 8-200(1) single-dwelling calculated load, Rule 8-106(3) interlock, Section 62 space-heating demand — verified July 2, 2026
- NFPA 70 National Electrical Code (NEC) 2023 — Article 220.82 Optional dwelling-unit calculation — verified July 2, 2026
Last reviewed June 28, 2026. Estimates are indicative — verify against current product specs and local requirements before ordering.
We're committed to keeping these tools accurate and improving them over time. If you'd like to contribute to their accuracy, or you run into any issues or errors, please email us at info@tradesppl.com.