Home Electrical Load & Service Size Calculator (NEC 220.82)

Applies the NEC 220.82 optional method to a single-family home to estimate service load in amps, pick the next standard service size, and show headroom for an EV charger or heat pump.

For homeowners and contractors planning an upgrade.

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Results will appear here once you enter your values.

How the calculation works

General load is 3 VA per sq ft of living area plus 4,500 VA for two small-appliance circuits and one laundry circuit. Add the range, dryer and water heater in kW times 1,000. The first 10,000 VA of that connected total counts at 100%, and anything above counts at 40%.

Defaults: 2,000 sq ft, a 12 kW range, 5 kW dryer, 4.5 kW water heater, 10 kW of cooling and 0 kW of heating. General load is 2,000 x 3 + 4,500 = 10,500 VA. Connected load is 10,500 + 21,500 = 32,000 VA. Demand is 10,000 + 22,000 x 0.4 = 18,800 VA. The larger of cooling (10,000 VA) and heating (0) is 10,000 VA, so the total is 28,800 VA, which is 120 A at 240 V. The next standard size is 125 A, with 5 A of headroom.

Add a 48 A EV charger and the total rises by 11,520 VA to 40,320 VA, or 168 A. The tool then returns a 175 A service with 7 A of headroom, and a minimum EV circuit of 60 A.

  • Service sizes: the next NEC 240.6(A) standard rating: 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350 or 400 A.
  • Over 400 A: shown as greater than 400 A with no headroom figure.
  • Inputs: any non-negative number up to 1 billion in each field.

What this tool is not

This is not an electrical design, a permit document, or electrical advice. The page tells you to have a licensed electrician perform the load calculation. It leaves out loads you do not enter, such as a pool pump, hot tub, welder or second range, which raises the real number. Panel bus rating, breaker space, wire size and utility service drop are separate questions.

  • Hire a licensed electrician: for any service upgrade, EV charger circuit or panel work.
  • Ask your AHJ: your city or county may use a different code edition or local amendments.
  • Utility: confirm your meter and service drop can support the new size.

Sources and next steps

NFPA 70, National Electrical Code: Section 220.82 (optional calculation for dwelling units, including the larger-of heating or cooling rule in (C)), Section 220.52 (small-appliance and laundry loads), Section 240.6(A) (standard ampere ratings) and Section 625.41 (EV supply equipment rating at 125% of continuous load). Check the edition your jurisdiction has adopted.

To size the wire for a single circuit, use the wire size calculator. To estimate EV charging cost, use the EV charging cost calculator, and to check a backup generator use the generator size calculator.

Frequently Asked Questions

Common questions about the Home Electrical Load & Service Size Calculator (NEC 220.82)

It is a way to size a dwelling's service or feeder without adding every load at full value. You total the general lighting and receptacle load (3 VA per sq ft), two 1,500 VA small-appliance circuits, a 1,500 VA laundry circuit, and the nameplate load of the range, dryer and water heater. The first 10 kVA counts at 100% and the remainder at 40%. Heating and cooling are handled separately: the larger of the cooling load or the heating load, at its own factor, is added on top.

Sources & References

International System of Units (SI): energy, work and heat

Energy, work and heat is measured in the joule (J); 1 cal = 4.184 J. Conversions between SI and other units use exact, internationally agreed factors maintained by NIST.
→Source: NIST — International System of Units (SI)

International System of Units (SI)

Authoritative definitions for energy, work and heat, from the BIPM SI Brochure (9th edition), the defining reference for the SI.
→Source: BIPM — SI Brochure (9th ed.)

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