How many amps does a house use?
A typical house calculates to somewhere between 74 A and 132 A under the NEC 220.82 optional method, which is what decides the service size. A 1,200 ft² house with gas heat and hot water comes to 73.7 A; the same style of house at 1,800 ft² is 81.7 A. Make that 1,800 ft² house all-electric with a heat pump and electric water heater and it jumps to 127.9 A, while going from 1,800 to 2,600 ft² all-electric adds only 4.0 A. The appliances drive the number; the floor area barely moves it. Actual draw on an ordinary day is far lower than any of these figures.
Updated September 23, 2026. Numbers on this page are computed by the same engine as the calculators, under NEC 2023.
Worked example: 1,800 ft² all-electric house with a heat pump
Calculated per NEC 2023Optional method (220.82)
Inputs
| NEC edition | NEC 2023 |
|---|---|
| Floor area | 1,800 ft² |
| Small-appliance circuits | 2 |
| Laundry circuits | 1 |
| Cooking | Electric range 12 kW |
| Clothes dryer | 5,000 VA |
| Appliances fastened in place | Dishwasher 1,200 VA; Garbage disposal 900 VA; Electric water heater 4,500 VA |
| Heating | Heat pump compressor 4,800 VA with 10,000 VA supplemental strip heat |
| Air conditioning | 3,600 VA |
Result
| Calculated load | 30,700 VAfrom 51,900 VA connected |
|---|---|
| Calculated current | 127.9 Aat 240 V |
| Minimum service rating | 150 A240.6(A) standard rating, not less than 100 A |
| Line item | NEC | Connected | Demand | Basis |
|---|---|---|---|---|
| General lighting and receptacles | 220.82(B)(1) | 5,400 VA | (in subtotal) | 1,800 ft² × 3 VA/ft² |
| Small-appliance and laundry circuits | 220.82(B)(2) | 4,500 VA | (in subtotal) | 3 circuits × 1500 VA |
| Appliances fastened in place | 220.82(B)(3) | 6,600 VA | (in subtotal) | 3 at nameplate |
| Ranges, ovens and cooking units | 220.82(B)(3) | 12,000 VA | (in subtotal) | 1 at nameplate |
| Clothes dryers | 220.82(B)(3) | 5,000 VA | (in subtotal) | 1 at nameplate |
| Permanently connected motors | 220.82(B)(4) | — | (in subtotal) | None |
| Other fixed loads | 220.82(B)(3) | — | (in subtotal) | None |
| EV supply equipment | 220.82(B)(3)a | — | (in subtotal) | None |
| General load after demand factors | 220.82(B) | 33,500 VA | 19,400 VA | First 10,000 VA at 100%; remaining 23,500 VA at 40% = 9,400 VA |
| Heat pump compressor at 100% plus supplemental heat at 65% | 220.82(C)(3) | 14,800 VA | 11,300 VA | 100% of 4,800 VA + 65% of 10,000 VA = 11,300 VA; largest selection |
| Air conditioning and cooling | 220.82(C)(1) | 3,600 VA | 0 VA | 100% of 3,600 VA; omitted, heating selection is larger |
Everything except heating and cooling goes into one general load, the first 10,000 VA at 100% and the rest at 40%; the heat pump is added under 220.82(C)(3) as compressor plus 65% of the strip heat. The result is 30,700 VA, 127.9 A, a 150 A minimum service.
Four houses side by side
Calculated per NEC 2023Optional method (220.82)
Inputs
| 1,200 ft², gas heat and water | 1,200 ft², 8 kW range, 5,000 VA dryer, gas heat and water, 2,400 VA air conditioner |
|---|---|
| 1,800 ft², gas heat and water | 1,800 ft², 8 kW range, 5,000 VA dryer, gas heat and water, 3,600 VA air conditioner |
| 1,800 ft², all-electric with heat pump | 1,800 ft², 12 kW range, 5,000 VA dryer, 4,500 VA water heater, heat pump 4,800 VA + 10 kW strips, 3,600 VA air conditioner |
| 2,600 ft², all-electric with heat pump | 2,600 ft², 12 kW range, 5,000 VA dryer, 4,500 VA water heater, heat pump 4,800 VA + 10 kW strips, 4,800 VA air conditioner |
Result
| 1,200 ft², gas heat and water | 73.7 A17,680 VA calculated; 100 A minimum service |
|---|---|
| 1,800 ft², gas heat and water | 81.7 A19,600 VA calculated; 100 A minimum service |
| 1,800 ft², all-electric with heat pump | 127.9 A30,700 VA calculated; 150 A minimum service |
| 2,600 ft², all-electric with heat pump | 131.9 A31,660 VA calculated; 150 A minimum service |
Going all-electric at 1,800 ft² adds 46.3 A to the calculation; adding 800 ft² of floor area adds 4.0 A. That ratio holds for most houses: fuel choice, then floor area.
Three different "amps" people mean
The number on the main breaker (100, 150 or 200 A) is the service rating, the most the service is allowed to carry. The calculated load is the NEC figure the service must be sized to cover, which is what the examples above report. And the actual current at any moment is what a clamp meter would read: a few amps overnight, perhaps 30 to 60 A with the dryer and air conditioner running together.
Utilities and electricians size by the calculated load because it has demand factors built in: it assumes you will not run every appliance at nameplate at once, but it protects for the realistic worst case. Actual usage matters for your bill, not for the wire size.
What pushes a house above 100 A
In the optional method the first 10,000 VA of general load counts fully and everything after it at 40%, then heating or cooling is added on top. A house crosses 100 A when the additions outrun that 40% discount:
- Electric space heating. The 1,800 ft² heat pump house carries 11,300 VA of heating demand; the gas version carries only its 3,600 VA air conditioner.
- An electric water heater (4,500 VA) and a larger range add 8,500 VA of connected load, which becomes 3,400 VA of demand past the first tier.
- An EV charger. A 40 A charger adds 9,600 VA of connected load and is the single most common reason an older 100 A house needs a second look.
How to get your own number
The free Home Load Estimator asks for the same inputs used here (floor area, appliances, heating and cooling) and returns the optional-method calculation with the minimum service rating. It runs the same engine as the contractor tool, so the number you get is the one an electrician would start from.
Frequently asked questions
- Is 100 A enough for a house today?
- For a gas-heated house without an EV charger, usually yes: both gas examples above calculate well under 100 A. All-electric houses generally need 150 A or more; the 1,800 ft² example needs a 150 A minimum.
- Why is my house on 200 A if it only calculates to 82 A?
- Because 200 A is the default for new construction in most of the country. The marginal cost is small and it leaves room for future loads. The calculation sets the minimum, not the maximum.
- Does square footage matter at all?
- Yes, but modestly. The NEC counts 3 VA per square foot for general lighting and receptacles (NEC 2023), so 800 extra square feet is 2,400 VA of connected load, most of which falls in the 40% tier. That is why the 2,600 ft² house is only 4.0 A above the 1,800 ft² one.
- How much current does a house actually draw?
- Far less than the calculated load most of the time. A typical home averages 1 to 2 kW over a day, about 4 to 8 A at 240 V, with peaks of 40 to 80 A when large 240 V appliances overlap.
Related questions
- 100 A vs 200 A service: which one does my house need?The same 1,600 ft² house calculated three ways under NEC 2023: gas appliances, all-electric, and all-electric with an EV charger. The optional and standard methods both shown, with the minimum service each requires.
- What size generator do I need for a 2,000 sq ft house?Two honest answers from one NEC calculation: the whole-house standby class and the essentials-only class for a 2,000 ft² gas-furnace home with an electric kitchen, laundry and central air.
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