Residential Electrical Load Calculator

This calculator uses the optional method for dwelling units in NEC 220.82 (2023 NEC). Enter the living area, the fixed appliances, the heating and cooling equipment and any EV chargers. It returns the calculated load in volt-amperes, the equivalent current at 240 V, and the smallest standard service rating that covers it. Print the page to save the worksheet as a PDF for the permit file.

When you need a load calculation

• Sizing a new service for a new house or addition.
• Adding a large load to an existing service: an EV charger, heat pump, electric range, hot tub or tankless water heater. Most inspectors will ask for a load calculation before approving it.
• Deciding between a service upgrade and load management. A calculation often shows that an existing 100 A or 150 A service can take the new load, or that an energy management system can avoid an upgrade.

For existing dwellings, NEC 220.83 offers a separate method for adding loads to an existing service, and 220.87 lets you use measured demand instead of a calculation (covered below).

How the optional method works (2023 NEC)

Step 1: Add up the general loads (220.82(B))

• General lighting and receptacles: 3 VA per square foot of living area (outside dimensions, not including open porches, garages or unfinished spaces not adaptable for future use).
• Small-appliance branch circuits: 1,500 VA each (at least two are required in the kitchen area).
• Laundry branch circuit: 1,500 VA.
• The nameplate rating of every appliance that is fastened in place, permanently connected, or on a dedicated circuit: range, wall oven, cooktop, dryer, water heater, dishwasher, disposal, microwave, well pump, EV charger and similar.
• Motors and low-power-factor loads at their nameplate VA.

Step 2: Apply the demand factor

• The first 10 kVA at 100%.
• The remainder at 40%.

Step 3: Add the heating and air-conditioning load (220.82(C))

Add the largest of the options in 220.82(C). In practice, that means 100% of the air-conditioning load, or the heat-pump load with its supplementary heat, or a percentage of electric space-heating load, whichever is largest. Heating and cooling are not added together because they do not run at the same time.

Step 4: Convert to amps

Divide the total VA by 240 V. Choose a service rating at or above that value, with room for growth.

Worked example: 2,400 ft² house

• First 10,000 VA at 100% = 10,000 VA
• Remaining 25,200 VA at 40% = 10,080 VA
• General load after demand = 20,080 VA
• Add air conditioning (gas heat, so cooling is the larger HVAC load): 5,000 VA
• Total calculated load = 25,080 VA
• 25,080 VA ÷ 240 V = 104.5 A

The minimum service is 125 A. Most electricians would install 150 A or 200 A to leave room for future loads.

Now add a 48 A EV charger (11,520 VA nameplate). The general load becomes 46,720 VA. After demand: 10,000 + (36,720 × 40%) = 24,688 VA. With the 5,000 VA air conditioning, the total is 29,688 VA, or 123.7 A. The house still fits within a 125 A calculated minimum, but an existing 100 A service would not. That is the calculation an inspector wants to see before approving the charger.

The standard method (220.40 and Part III) in brief

The optional method is a shortcut for single dwellings. The standard method in Article 220, Part III, works for every occupancy and is the one you must use when 220.82 does not apply. It calculates each load category separately and applies a demand factor to each:

1. General lighting and receptacles: 3 VA per square foot for dwellings (Table 220.12, 2023 NEC).
2. Small-appliance and laundry circuits: 1,500 VA each (220.52), added to the lighting load.
3. Apply the lighting demand factors of Table 220.42 to that combined total. For dwelling units, the first 3,000 VA is taken at 100% and the remainder at 35% in the range any single house falls into.
4. Fastened-in-place appliances (water heater, dishwasher, disposal and similar): at nameplate, or at 75% of the total when there are four or more (220.53). Dryers, ranges, heating and cooling are handled separately.
5. Dryer: 5,000 VA or the nameplate rating, whichever is larger (220.54).
6. Ranges and cooking equipment: the demand values of Table 220.55 and its notes, not the nameplate.
7. Heating and cooling: only the larger of the two noncoincident loads (220.60).
8. Motors: per 220.50, which sends you to the Article 430 rules for the largest motor.
9. Add the categories and divide by 240 V.

For the lighting part of the 2,400 ft² example above: 7,200 + 3,000 + 1,500 = 11,700 VA. The first 3,000 VA at 100% plus 8,700 × 35% = 3,045 VA gives 6,045 VA. The standard method usually lands higher than the optional method for the same house, which is why most residential calculations use 220.82 where it is allowed.

Adding an EV charger or heat pump: the 220.87 existing-load method

Instead of calculating the existing load, 220.87 lets you measure it:

1. Get the maximum demand for the past 12 months from the utility. If a year of data is not available, the exception allows recording the maximum demand (the highest average kW over a 15-minute interval) continuously for at least 30 days while the building is occupied, with seasonal loads such as heating or air conditioning running.
2. Multiply that maximum demand by 125%.
3. Add the new load at its calculated value.
4. The total must not exceed the ampacity of the feeder or the rating of the service.

Example. A 100 A, 240 V service is rated 24,000 VA. The utility reports a 12-month peak of 11,000 VA. 11,000 × 125% = 13,750 VA of existing load.

Turning the charger down, or adding an energy management system, is often cheaper than a service upgrade. Confirm with the AHJ which utility data they accept. Where the service has a renewable energy system (solar PV or wind) or uses peak load shaving, 220.87 does not permit the measured-demand method, because on-site generation hides part of the load; use a calculated load instead.

What changes in the 2026 NEC

The 2026 NEC moves load calculations out of Article 220 into a new Article 120 in Chapter 1, so every section number changes (220.82 becomes 120.82). Published summaries also report a lower general lighting load for dwellings (2 VA per square foot instead of 3) and changes to several demand factors, including EV charging equipment in existing dwellings.

Only some states have adopted the 2026 edition so far, and adoption continues through 2026–2027. Always use the edition your jurisdiction enforces, and confirm the values in an authorized copy of the NEC.

Common mistakes

• Using the standard method's lighting demand factors in the optional method. They are separate methods; don't mix them.
• Adding heating and cooling together. Use the larger one, per 220.82(C).
• Forgetting appliances on dedicated circuits, such as a well pump, microwave, or garage heater.
• Using breaker size instead of nameplate. The optional method uses nameplate ratings.
• Using 220.82 where it doesn't apply. The optional method covers a dwelling unit served by a single 3-wire, 120/240 V or 208Y/120 V set of service or feeder conductors with an ampacity of 100 A or more. It does not apply to three-phase services.

Frequently asked questions

How do I calculate my home's electrical load?

Add 3 VA per square foot for lighting, 1,500 VA for each small-appliance circuit and the laundry circuit, and the nameplate rating of each fixed appliance. Take the first 10,000 VA at 100% and the rest at 40%, add the larger of heating or cooling, and divide by 240 to get amps (2023 NEC optional method).

What is the difference between the standard and optional methods?

The standard method applies separate demand factors to lighting, appliances, dryers, ranges and HVAC. The optional method in 220.82 adds most loads together, takes the first 10 kVA at 100% and the rest at 40%, then adds the larger HVAC load. It is only for a dwelling served by a single 120/240 V or 208Y/120 V 3-wire set of conductors rated 100 A or more.

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

Often yes, if the load calculation shows room, or if you use a lower charger setting or a load management system. A 100 A service with gas heat and appliances can sometimes take a 24–32 A charger. Run the calculation with the actual charger setting.

What size service do I need for a 2,500 square foot house?

It depends far more on the appliances and heating type than on square footage. An all-electric house with a heat pump, electric range, dryer, water heater and EV charger typically needs 200 A. A house with gas heat, range and water heater often calculates under 100 A.

Is a load calculation required for a permit?

Many jurisdictions require one for new services, service upgrades, and large additions like EV chargers and heat pumps. Check with your local inspection office.

Related

• What Size Wire for a 200 Amp Service?
• What Size Wire for a 100 Amp Service?
• Panel Schedule Template and Generator
• Voltage Drop Calculator

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Estimating the service upgrade? Once you know the size, SparkQuote builds the bid: meter base, panel, service conductors, grounding, permit and labor. Try the electrical estimator.

Last updated: October 6, 2026. 2023 NEC 220.82 method; 2026 NEC Article 120 values must be verified against an authorized copy before enabling the 2026 option in the tool. Check results against the code edition and local amendments your jurisdiction enforces and with the AHJ; electrical work should be done by qualified people.