Electrical load calculator: what size panel does the house need?

Enter the house size and what runs on electricity. You get the calculated load in VA and amps at 240 V, the panel size that fits (100, 125, 150 or 200 A) and how much room is left, with every step of the math. Everything stays in your browser.

House
Outside dimensions. Leave out open porches, the garage and unfinished spaces.
1,500 VA each. Most homes have at least 2.
1,500 VA each.
Appliances (nameplate watts)

Check the ones in the house, after the job. Change the watts to match the nameplate.

Use at least 5,000 W.
Tank: often 4,500 W. Whole-house tankless: often 18,000–27,000 W.
Heating and cooling

Only the largest of these counts, because heat and AC don’t run at the same time.

Your estimate

Lighting and outlets
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Small-appliance and laundry circuits
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Appliances at nameplate
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General load
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First 10,000 VA at 100%
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Remainder at 40%
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General load after demand factor
—
Heating or cooling (largest)
—
Calculated load
—
Amps at 240 V
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Panel size
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Room left
—

Estimate only. This uses the NEC 220.82 optional method (2023 NEC) for one dwelling at 120/240 V. Your local code edition, amendments, utility rules and the actual nameplates can change the answer. Confirm with a licensed electrician and your local building or permit office before you buy equipment or quote the job.

How the NEC 220.82 optional method works

  1. Lighting and outlets: 3 VA per square foot of living area.
  2. Add 1,500 VA for each 20 A small-appliance circuit and each laundry circuit.
  3. Add the nameplate rating of the appliances: range, ovens, cooktops, dryer, water heater, EV charger, dishwasher, disposal, built-in microwave, pool or spa equipment and other fixed appliances.
  4. Take the first 10,000 VA of that general load at 100% and the rest at 40%.
  5. Add the largest heating or cooling item: AC at 100%, a heat pump at 100% plus 65% of its heat strip, central electric heat or 1–3 space heaters at 65%, or 4 or more separately controlled heaters at 40%.
  6. Divide the total by 240 V to get amps. The service or panel must be at least that size (and at least 100 A for this method).

Calculated load by house size

12 kW range, 5 kW dryer, 4.5 kW tank water heater, 1.2 kW dishwasher, 2 small-appliance circuits and 1 laundry circuit. Computed with the same formula as the calculator above.

HouseHeating/coolingLoadAmpsPanel
1,500 sq ftCentral AC 4,800 VA23,480 VA97.8 A100 A
1,500 sq ftCentral AC + EV charger 7,680 W26,552 VA110.6 A125 A
1,500 sq ftHeat pump 5,760 VA + 10 kW strip + EV charger34,012 VA141.7 A150 A
2,000 sq ftCentral AC 4,800 VA24,080 VA100.3 A125 A
2,000 sq ftCentral AC + EV charger 7,680 W27,152 VA113.1 A125 A
2,000 sq ftHeat pump 5,760 VA + 10 kW strip + EV charger34,612 VA144.2 A150 A
3,000 sq ftCentral AC 4,800 VA25,280 VA105.3 A125 A
3,000 sq ftCentral AC + EV charger 7,680 W28,352 VA118.1 A125 A
3,000 sq ftHeat pump 5,760 VA + 10 kW strip + EV charger35,812 VA149.2 A150 A

Can my panel handle an EV charger?

Turn on the EV charger with its nameplate watts, enter the existing panel size from the main breaker, and look at the room left. If the result goes over the panel, common options are a smaller charger setting, a load management device, or a service upgrade. For an existing home, an electrician may use NEC 220.83 or a year of utility demand data (220.87) instead; those can give a different answer.

What this calculator leaves out

It does not size wire, breakers or the neutral, and it does not cover multifamily buildings, three-phase service, 208 V service or the standard method (220.40 to 220.61). Motors over the nameplate, local amendments and the utility’s own rules are not included.

Questions

What is the difference between the optional method and the standard method?

The NEC 220.82 optional method adds up the general load and takes the first 10,000 VA at 100% and the rest at 40%, then adds the largest heating or cooling load. The standard method uses separate demand factors for lighting, ranges, dryers and appliances. For a single home the optional method usually gives a smaller, still code-based number. This calculator uses the optional method.

Does a 2,000 sq ft house need a 200 A panel?

Not always. A 2,000 sq ft home with an electric range, dryer, water heater and dishwasher, an EV charger and a heat pump with a 10 kW heat strip comes to about 34,600 VA, or about 144 A, so a 150 A panel fits with little room left. A gas home with central AC needs much less. Enter your own appliances above.

How many watts does an EV charger use?

A 40 A Level 2 charger on a 50 A circuit uses about 9,600 W at 240 V if it charges at the full 40 A, and 7,680 W at 32 A. Use the nameplate or the setting the electrician will program.

Is this calculator good enough for a permit?

No. It is a planning estimate. The permit office may require a load calculation signed by a licensed electrician, on their own form, with the real nameplates.

Is this calculator free? Does it save my numbers?

Yes, it is free and needs no sign-up. Nothing is saved or sent anywhere; the math runs in your browser and is gone when you close the page.

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