Electrical Load Calculator

Calculate the service load of a house in VA and amps with the NEC 220.82 optional method from floor area, appliances, heating and cooling, and see what service size fits.

By CalcBuilt Editorial TeamUpdated September 10, 2026Formulas checked against manufacturer specs, see how we calculate.

Quick answer: The NEC 220.82 optional method adds 3 VA per square foot, 4,500 VA for the small-appliance and laundry circuits and the nameplate of every fastened appliance, takes the first 10 kVA at 100% and the rest at 40%, then adds the larger of heating or cooling. A 2,000 sq ft house with the default appliances and 5 kW of air conditioning comes to 25,080 VA, or 104.5 A at 240 V, which calls for a 150 A service.

Your measurements

Plan view from above: area is length times width.

Floor area (living space)sq ftHeated or cooled floor area, outside dimensions, not counting open porches, garages or unfinished space.Electric range (kW)Nameplate rating. Typical ranges are 8 to 12 kW; enter 0 for gas.Electric dryer (kW)Nameplate or 5 kW minimum per NEC 220.54; enter 0 for gas.Electric water heater (kW)Most 40 to 50 gallon tanks are 4.5 kW. Enter 0 for gas or leave a tankless unit's nameplate (often 18 to 36 kW).Dishwasher (kW)Other fixed appliances (kW)Disposal, built-in microwave, well pump, sump pump, hot tub (6 to 11 kW nameplate) and similar hard-wired or dedicated-circuit loads. Do not put an EV charger here; the result row adds it at 100 percent.Air conditioning (kW)Nameplate of the condenser plus the air handler: RLA x 240 for the compressor plus the blower. A 3 ton unit is roughly 4 to 5 kW.Electric heat (kW)Strip heat or baseboards at nameplate. For a heat pump with backup strips, enter the compressor plus 65 percent of the strips (NEC 220.82(C)(3)): a 5 kW heat pump with 10 kW of strips is 11.5 kW. Only the larger of heating or cooling counts.

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Service load at 240 V104.5 AAll results

Results

Service load at 240 V: 104.5 A; 25,080 VA calculated load by the NEC 220.82 optional method
Calculated load: 25,080 VA; 20,080 VA after the demand factor plus 5,000 VA for the larger of 5 kW cooling or 0 kW heating
General load before demand factor: 35,200 VA; 6,000 VA lighting and receptacles at 3 VA per sq ft, 4,500 VA for two small-appliance circuits and laundry, 24,700 VA of fastened appliances
Recommended service size: 150 A; Next standard size with at least 15% headroom above 104.5 A
Adding an EV charger: Add 7.2 to 11.5 kW; A Level 2 charger (30 to 48 A) is a continuous load added at 100% (2023 NEC 220.57 sets 7,200 VA as the minimum), which would raise the load to 134.5 to 152.4 A
Planning estimate only: NEC 220.82; Optional method for a single dwelling with a 100 A or larger service. A licensed electrician and the local authority govern the final service size, and the utility approves it.

Electrical Load formula

General load (VA) = 3 x Floor area (sq ft) + 1,500 x 2 small-appliance circuits + 1,500 laundry + Fastened appliances (W)
After demand factor = 10,000 + (General load - 10,000) x 0.40   (all of it if under 10,000 VA)
Calculated load = After demand factor + larger of heating or cooling (W);  Amps = Calculated load / 240
Service size = next standard size (100, 150, 200, 400 A) at or above Amps x 1.15

Worked example

A 2,800 sq ft house with a 12 kW range, 5.5 kW dryer, 4.5 kW water heater, 1.5 kW dishwasher, 3 kW of other appliances, 6 kW of air conditioning and 15 kW of electric strip heat. General load: 3 x 2,800 = 8,400, plus 3,000 for small-appliance circuits and 1,500 for laundry, is 12,900 VA. Appliances add 12 + 5.5 + 4.5 + 1.5 + 3 = 26.5 kW, or 26,500 VA, for 39,400 VA before demand factors. The first 10,000 counts in full and the remaining 29,400 x 0.40 = 11,760, so 21,760 VA. Heating (15,000 VA) is larger than cooling, so the calculated load is 36,760 VA, or 36,760 / 240 = 153.2 A. With 15% headroom, 153.2 x 1.15 = 176.2 A, so a 200 A service.

If the same house had gas heat, the 6,000 VA of air conditioning would be added instead: 21,760 + 6,000 = 27,760 VA, or 115.7 A. Then 115.7 x 1.15 = 133 A, and a 150 A service would do.

Quick reference

Calculated load with the default appliances (24.7 kW fastened), by floor area
Floor area	Load with 5 kW AC	Amps at 240 V	Load with 15 kW electric heat	Amps at 240 V
1,000 sq ft	23,880 VA	99.5 A	33,880 VA	141.2 A
1,500 sq ft	24,480 VA	102.0 A	34,480 VA	143.7 A
2,000 sq ft	25,080 VA	104.5 A	35,080 VA	146.2 A
2,500 sq ft	25,680 VA	107.0 A	35,680 VA	148.7 A
3,000 sq ft	26,280 VA	109.5 A	36,280 VA	151.2 A
4,000 sq ft	27,480 VA	114.5 A	37,480 VA	156.2 A

How the optional method works

NEC Article 220 offers two ways to size a dwelling service. The standard method applies separate demand factors to lighting, ranges, dryers and appliances. The optional method in 220.82 is simpler and usually gives a slightly lower number: lump the lighting, small-appliance, laundry and fastened appliance loads together, count the first 10 kVA in full and the rest at 40%, then add the heating or cooling equipment, whichever is larger, at 100%.

The 40% factor reflects diversity. A range, dryer, water heater and dishwasher are all installed, but they do not all run at full nameplate at the same moment. Heating and cooling get no discount because a heat pump or furnace blower runs for hours, and the two are never on together, so only the larger one counts. The NEC allows central electric space heating to be taken at 65% under 220.82(C); this calculator keeps it at 100%, which is conservative.

Choosing the service size

The calculated amps only have to fit under the service rating, but a panel run at 95% of its rating leaves no room for a hot tub, an EV charger or a heat pump later. The calculator picks the next standard size with at least 15% of headroom, which is why a 104.5 A calculation lands on 150 A rather than a 100 A service. A 200 A service is the default for new construction: 4/0 aluminum or 2/0 copper (NEC 310.12) and a 40 space panel. At build time it is typically $200 to $400 more than 150 A.

Electrification is what pushes existing homes over the line. Replacing a gas range, dryer, water heater and furnace with electric units can add 30 kW of nameplate, and a Level 2 charger adds 7 to 11.5 kW that counts at 100% because it is continuous. Before paying for an upgrade, ask about NEC 220.87. The utility's 12 months of demand data times 1.25 often shows a 100 A house peaking at 40 to 60 A, which leaves room for a 32 A charger. An EV energy management system (625.42) that caps the charger is the other way around a new service.

When the upgrade is real, the order is permit, the utility's service application, then cutover 2 to 8 weeks out. The utility checks its transformer and drop, and the meter base is built to its spec, not the NEC. NEC 230.85 puts an emergency disconnect outside, so a meter-main is the common choice and the indoor panel becomes a subpanel with neutrals and grounds separated.

What this calculator leaves out

The result is a calculated load. Not included: service conductor sizing, the meter base and mast, and the ground rods. NEC 230.67 (2020) also requires a surge protector on a new or replaced service, typically $100 to $250. Also the permit (typically $150 to $400) and any utility fee for a transformer or drop upgrade.

Code limits that apply

NEC 220.82
One dwelling with a 100 A or larger service: first 10 kVA at 100%, remainder at 40%
If you miss it: An optional method calc on a 60 A service is bounced at plan review; the standard method is redone or the service upgraded to 100 A
NEC 220.82(B)
3 VA per sq ft, 4,500 VA for small-appliance and laundry circuits, appliances at nameplate
If you miss it: A calc that skips the 4,500 VA of required circuits or measures net floor area comes in low; plan review sends it back for a redo
NEC 220.82(C)
Larger of heating or cooling counts; heat pump at compressor plus 65% of backup strips
If you miss it: Counting the strips at 100% oversizes the service by a step; counting only the compressor undersizes it and the main trips on defrost
NEC 220.57
EV charging equipment added at 7,200 VA or the nameplate rating, whichever is larger, at 100%
If you miss it: A 48 A charger added to a house calculating 104 A pushes the load past 150 A; the permit waits on a 200 A upgrade or a load manager
NEC 220.87
12 months of peak demand data times 1.25 stands in for the calculation on an existing service
If you miss it: Without the utility demand printout, a 100 A house adding a charger is calculated to 136 A and sold a $4,000 upgrade it may not need
NEC 310.12
Dwelling service conductors at 83% of the rating: 200 A on 2/0 copper or 4/0 aluminum
If you miss it: A 200 A meter-main fed with 2 AWG copper is red-tagged at the service inspection; the mast is repulled in 2/0 copper or 4/0 aluminum
NEC 230.85
New or replaced dwelling service gets an emergency disconnect outside, readily accessible
If you miss it: A panel swap with the main left indoors fails the service inspection; a meter-main is added and the indoor panel becomes a subpanel

Provision	Limit	If you miss it
NEC 220.82	One dwelling with a 100 A or larger service: first 10 kVA at 100%, remainder at 40%	An optional method calc on a 60 A service is bounced at plan review; the standard method is redone or the service upgraded to 100 A
NEC 220.82(B)	3 VA per sq ft, 4,500 VA for small-appliance and laundry circuits, appliances at nameplate	A calc that skips the 4,500 VA of required circuits or measures net floor area comes in low; plan review sends it back for a redo
NEC 220.82(C)	Larger of heating or cooling counts; heat pump at compressor plus 65% of backup strips	Counting the strips at 100% oversizes the service by a step; counting only the compressor undersizes it and the main trips on defrost
NEC 220.57	EV charging equipment added at 7,200 VA or the nameplate rating, whichever is larger, at 100%	A 48 A charger added to a house calculating 104 A pushes the load past 150 A; the permit waits on a 200 A upgrade or a load manager
NEC 220.87	12 months of peak demand data times 1.25 stands in for the calculation on an existing service	Without the utility demand printout, a 100 A house adding a charger is calculated to 136 A and sold a $4,000 upgrade it may not need
NEC 310.12	Dwelling service conductors at 83% of the rating: 200 A on 2/0 copper or 4/0 aluminum	A 200 A meter-main fed with 2 AWG copper is red-tagged at the service inspection; the mast is repulled in 2/0 copper or 4/0 aluminum
NEC 230.85	New or replaced dwelling service gets an emergency disconnect outside, readily accessible	A panel swap with the main left indoors fails the service inspection; a meter-main is added and the indoor panel becomes a subpanel

Rows marked checked produce a warning in the results when an entry crosses the limit. The others are on the plans or on site and this calculator does not test them. Local amendments can be stricter; the adopted edition and the inspector govern.

Mistakes that cost money

A 200 A upgrade runs typically $2,500 to $6,000, and the utility schedules the cutover 2 to 8 weeks out; call them before the electrician.
NEC 220.87 lets 12 months of peak demand data times 1.25 stand in for the calculation; that often fits an EV charger without an upgrade.
New or replaced services need an outdoor emergency disconnect under NEC 230.85 (2020); a meter-main combo covers it and saves a separate box.
Heat pump plus strips is not larger-of-two: NEC 220.82(C)(3) counts the compressor at 100 percent plus 65 percent of the strips.
Replacing the panel brings grounding up to code: two rods 6 ft apart (NEC 250.53(A)(2)) and bonding jumpers to the water and gas piping.
When the disconnect moves outside, the old panel becomes a subpanel: pull the bonding screw and separate neutrals from grounds (NEC 250.24(A)(5)).

Key facts

NEC 220.82 lets a single-family dwelling served at 120/240 V with a 100 A or larger service use the optional method: the first 10 kVA of general load at 100% and the remainder at 40%.
General lighting and receptacle load for a dwelling is 3 VA per square foot of floor area, and each of the two required 20 A small-appliance circuits and the laundry circuit counts 1,500 VA.
A 100 A service at 240 V delivers 24,000 VA, a 150 A service 36,000 VA and a 200 A service 48,000 VA.
A Level 2 EV charger on a 40 A circuit draws 32 A continuous (7.7 kW); on a 60 A circuit, 48 A (11.5 kW). NEC 625.41 and 625.42 require 125% of that rating for the circuit.
Typical nameplates: electric ranges 8 to 12 kW, dryers 5 to 5.6 kW, 40 to 50 gallon tank water heaters 4.5 kW, and whole-house tankless electric heaters 18 to 36 kW.

Frequently asked questions

How many amps does a 2,000 sq ft house need?

By the NEC optional method, a 2,000 sq ft all-electric house with a 12 kW range, 5 kW dryer, 4.5 kW water heater and 5 kW of air conditioning calculates to about 25,080 VA, or 104.5 A. That fits a 150 A service with room to grow; a 200 A service is the common choice for new construction.

Can I add an EV charger to a 100 A service?

Often not without a load management device. The default house already calculates to 104.5 A, and a 40 A Level 2 charger adds 7,680 VA at 100%, which pushes the load to about 136.5 A. A 48 A charger takes it to 152.4 A.

When do I need a 200 amp service?

When the calculated load is above about 130 A, since 150 x 1.15 headroom runs out there. With the default appliances, replacing the 5 kW air conditioner with 15 kW of electric heat raises the 2,000 sq ft house to 35,080 VA, or 146.2 A, which needs 200 A.

Do I need a panel upgrade to add a heat pump or an EV charger?

Run the numbers before assuming so. Swapping the default house's gas furnace for a 3 ton heat pump with 10 kW of strips puts about 11.5 kW in the heating slot (compressor plus 65% of the strips), which takes the 2,000 sq ft house from 104.5 A to about 131.6 A: still a 150 A service. On a 100 A service, NEC 220.87 with 12 months of utility demand data, or an EV energy management system that caps the charger, often avoids the upgrade.

Sources and references

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