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 9, 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 and similar hard-wired or dedicated-circuit loads.Air conditioning (kW)Nameplate of the condenser plus the air handler. A 3 ton unit is roughly 4 to 5 kW.Electric heat (kW)Strip heat, baseboards or a heat pump's backup heat. Only the larger of heating or cooling counts.

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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%, 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.

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 in most of the country and costs little more than 150 A at build time.

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 ordering a panel or a service upgrade, have a licensed electrician do the formal calculation under the NEC edition your jurisdiction has adopted; the utility also has to approve the service size.

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.

What is the difference between the standard and optional load calculation?

The standard method (NEC 220.40 through 220.61) applies separate demand tables for lighting, ranges, dryers and appliances. The optional method (220.82) lumps them together with a single 100%/40% split and is allowed for single-family dwellings with a 100 A or larger service. Both are accepted by inspectors.

Sources and references

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