Tradesman Calculator
Menu
Electrical calculators

Electrical load calculator

Add up a house’s lighting, kitchen circuits, appliances and heating or cooling by the NEC 220.82 optional method to get the service load in amps at 240 V, the minimum standard service rating and a common panel size. Every step is shown so you or an inspector can check it.

General
ft²

Outside dimensions of every floor; leave out the garage, open porches and unfinished space.

20 A kitchen and dining receptacle circuits; at least 2.

Appliances
VA

Nameplate kW × 1,000. 0 for a gas range.

VA

0 for a gas dryer.

VA

Electric tank: one element’s rating. 0 for gas.

VA
VA
Heating and cooling
VA

About 1,600 VA per ton.

VA

Total nameplate of all electric heat; ignored for gas.

Advanced options
Appliances
VA
VA
VA
VA

Nameplate; counted at 7,200 VA minimum if present (NEC 220.57).

VA

Well pump, hot tub, sump pump, fastened-in-place heaters and the like.

Calculated service load at 240 V

101.8 A

minimum 110 A service · common panel 125 A

Lighting and receptacles
6,000 VA
3 VA × 2,000 ft²
Small-appliance circuits
3,000 VA
2 × 1,500 VA
Laundry circuits
1,500 VA
1 × 1,500 VA
Appliances (nameplate)
23,600 VA
range 12,000 + dryer 5,000 + water heater 4,500 + dishwasher 1,200 + disposal 900
General load
34,100 VA
6,000 + 3,000 + 1,500 + 23,600
General load after demand factor
19,640 VA
10,000 + 40% × 24,100
Heating or cooling
4,800 VA
Air conditioning at 100% (gas or no electric heat), 220.82(C)
Total demand load
24,440 VA
19,640 + 4,800; ÷ 240 V = 101.8 A
Minimum service rating
110 A
Next standard rating at or above 101.8 A (240.6(A))
Common panel size
125 A
Optional method (220.82(A)): one dwelling unit with a 100 A or larger service
Service load 24,440 VA = 101.8 A → 110 AGeneral load 34,100 VA as connected; after the demand factor 19,640 VA (10,000 at 100% + 9,640 at 40%, 14,460 not counted). Heating or cooling 4,800 VA. Total 24,440 VA ÷ 240 V = 101.8 A; minimum 110 A service, common panel 125 A.100 A125 A150 A200 AAs connected: general 34,100 VADemand: 10,000 + 9,640 + 4,800 HVAC = 24,440 VA01020301020304050kVA101.8 A0424,440 VA ÷ 240 V = 101.8 A → minimum 110 A serviceCommon panel 125 A
Default example: 2,000 ft² house with gas heat and a 4,800 VA air conditioner. Top bar: general load as connected; bottom bar: demand load to the same kVA scale, with service sizes at 240 V marked.
  1. 01 First 10 kVA of the general load, counted at 100%
  2. 02 General load above 10 kVA at 40%; hatched: the 60% not counted
  3. 03 Heating or cooling, the larger 220.82(C) value
  4. 04 Total demand load and amps at 240 V

How the service load is calculated

The optional method in NEC 220.82 lumps almost everything in the house into one general load, discounts it, and then adds heating or cooling on top.

general load = 3 VA × floor area + 1,500 VA × small-appliance circuits + 1,500 VA × laundry circuits + every appliance nameplate

Appliances are the ones fastened in place or on their own circuit: range, wall oven, cooktop, dryer, water heater, dishwasher, disposal, built-in microwave, EV charger, well pump, hot tub and the like. An EV charger counts at 7,200 VA or its nameplate, whichever is larger (220.57).

demand load = first 10,000 VA at 100% + the rest at 40%

Then pick the heating or cooling figure from 220.82(C), whichever is largest:

gas heat: air conditioner at 100%

electric furnace, or fewer than four separately controlled heaters: the larger of the air conditioner or 65% of the heat

baseboard or room heaters on four or more thermostats: the larger of the air conditioner or 40% of the heat

heat pump: compressor at 100% + 65% of the backup strips

The heat-pump line is conservative: 220.82(C) lets you leave the compressor out of the heating figure when its controls stop it running at the same time as the backup strips.

total load = demand load + heating or cooling

amps = total load ÷ 240 V

minimum service = next standard rating at or above the amps (240.6(A)), never under 100 A

The common panel size is the first of 100, 125, 150, 200, 225, 400 A that covers the minimum.

Worked example: 2,000 ft² house

The calculator opens on a 2,000 ft² house with gas heat, a 12,000 VA range, 5,000 VA dryer, 4,500 VA water heater, 1,200 VA dishwasher, 900 VA disposal and a 4,800 VA air conditioner (about 3 tons).

  1. Lighting: 3 × 2,000 = 6,000 VA. Kitchen: 2 × 1,500 = 3,000 VA. Laundry: 1 × 1,500 = 1,500 VA.
  2. Appliances: 12,000 + 5,000 + 4,500 + 1,200 + 900 = 23,600 VA.
  3. General load: 6,000 + 3,000 + 1,500 + 23,600 = 34,100 VA.
  4. Demand: 10,000 + 40% × 24,100 = 19,640 VA. The other 60% of the remainder, 14,460 VA, is not counted.
  5. Cooling: gas heat, so the air conditioner counts at 100%, 4,800 VA.
  6. Total: 19,640 + 4,800 = 24,440 VA ÷ 240 V = 101.8 A.
  7. The next standard rating above 101.8 A is 110 A, so the minimum service is 110 A and the common panel is 125 A.

Add a 7,200 VA EV charger and the same house comes to 113.8 A (125 A minimum). Swap the gas furnace for a 15 kW electric one as well and it reaches 134.5 A, a 150 A panel. A 3,500 ft² all-electric house with a 9,600 VA charger lands at 173.1 A, a 200 A panel.

Reading nameplates

  • Use the nameplate rating, not a typical wattage. Ranges and cooktops list kW: 12 kW is 12,000 VA.
  • For a tank water heater with two elements that cannot run together, use the rating on the label, usually one element.
  • Enter the air conditioner or heat pump from the condensing unit’s nameplate. If you only know the tonnage, about 1,600 VA per ton is a rough starting figure; replace it with the nameplate before you file.
  • Heat-pump strips are listed in kW on the air handler. Enter the full strip rating; the calculator applies the 65%.
  • Floor area is measured from the outside of the walls on every floor. Leave out the garage, open porches and unfinished spaces that can’t be finished later.
  • Kitchens need at least 2 small-appliance circuits (210.11(C)(1)); count every 20 A countertop and dining circuit you actually have.

Code notes and when to call an electrician

The optional method is only for one dwelling unit with a service of 100 A or more (220.82(A)). Adding a load to an existing house is calculated under 220.83, and apartment buildings under 220.84. The standard method in Article 220 Part III uses different demand factors and gives a different number. Your inspector may ask which method you used, so print the result rows with the permit.

The service size also sets the service conductors, grounding electrode conductor and meter base, and the utility has its own requirements. Have a licensed electrician confirm the load and pull the permit before any service upgrade, and treat this calculation as the starting point for that conversation.

Sources

  • NFPA 70, National Electrical Code, 2023 edition, 220.82 (dwelling unit optional calculation): (A) scope, (B) general loads and the 10 kVA / 40% demand, (C) heating and air-conditioning load
  • NFPA 70, 2023, 220.57 (electric vehicle supply equipment load: 7,200 VA or nameplate, whichever is larger) and 220.5(C) (floor area from outside dimensions)
  • NFPA 70, 2023, 210.11(C)(1) (at least two small-appliance branch circuits)
  • NFPA 70, 2023, 230.79(C) (100 A minimum service disconnect for a one-family dwelling) and 240.6(A) (standard ampere ratings)

Frequently asked questions

How does the NEC optional method calculate a house’s service load?

Add the general loads (lighting, small-appliance and laundry circuits, and every nameplate appliance), count the first 10 kVA at 100% and everything above it at 40%, then add the larger of the heating or cooling load. Divide the total VA by 240 V for amps.

How many VA per square foot do I use for lighting?

NEC 220.82(B)(1) uses 3 VA per square foot of floor area, measured from the outside dimensions. Each small-appliance circuit and each laundry circuit adds 1,500 VA.

Is a 100 A service enough for a 2,000 square foot house?

Often it is close. A 2,000 ft² house with gas heat, an electric range, dryer and water heater and a 4,800 VA air conditioner comes to 101.8 A, so the minimum is 110 A and a 125 A panel is the usual choice. Electric heat or an EV charger pushes it higher.

How does an EV charger count in a load calculation?

NEC 220.57 counts EV charging equipment at 7,200 VA or its nameplate rating, whichever is larger. Adding a 7,200 VA charger to the example house raises it from 101.8 A to 113.8 A.

What is the minimum service size for a house?

NEC 230.79(C) requires at least 100 A for a one-family dwelling, even when the calculated load is lower. An 800 ft² home with gas appliances calculates to about 27.5 A but still needs 100 A.

Why does the calculation use only heating or cooling, not both?

A furnace and an air conditioner do not run at the same time, so 220.82(C) counts only the largest of its heating and cooling options. A heat pump is different: its compressor runs with the backup strips, so both are added.

Can I use this for an addition, an apartment building or a commercial space?

No. The optional method in 220.82 is for one dwelling unit served by a 100 A or larger service. Loads added to an existing dwelling use 220.83, multifamily buildings use 220.84, and other occupancies use the standard method in Article 220 Part III.

Guides

By Tradesman Calculator editorial team · Formulas reviewed · How we check accuracy · Report an error