Electrical Panel Calculator

Estimate your home's electrical service load with the NEC optional method and see how much headroom your panel has.

By Konstantin Iakovlev · Updated September 2026 · Source: IAEI Magazine: Residential Service Calculations in the National Electrical Code (NEC Article 220)

sq ft
kW
kW
kW
kW
A

Calculated Load

92A

Smallest Standard Service

100A

Headroom on Current Service

108A

NEC 220.82 Optional Method

Lighting and receptacles (3 VA per sq ft)6,000 VA
Small-appliance and laundry circuits4,500 VA
Fixed appliances and EV charger17,000 VA
General load27,500 VA
After demand factor (first 10 kVA at 100%, rest at 40%)17,000 VA
Heating or cooling, whichever is larger+ 5,000 VA
Total22,000 VA ÷ 240 V = 92 A

A planning estimate, not a permit calculation. A licensed electrician does the Article 220 load calculation for your home and local code edition; a service upgrade needs a permit and inspection, and the utility may need to upgrade the service drop.

Use the Electrical Panel Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only. Results are estimates from the numbers you enter and the assumptions described on this page; check them against local building codes, product specifications and current prices, and have structural, electrical or gas work designed or checked by a licensed professional.

How It Works

Knowing whether your service panel can carry everything your home draws is a safety question as much as a planning one. The tool estimates your home's service load with the National Electrical Code's optional method for dwellings and compares it with the service you have, a planning figure to take into a licensed electrician's load calculation.

It follows NEC Article 220.82: 3 volt-amperes per square foot of floor area for general lighting and receptacles, 1,500 volt-amperes for each small-appliance and laundry circuit, and the nameplate ratings of fixed appliances, including any new EV charger, make up the general load. The first 10 kVA counts at 100% and the rest at 40%; then the larger of the air-conditioning load (100% of nameplate) or electric space heat (65%) is added in full. The total in volt-amperes divided by 240 volts gives the load in amps, which the tool compares with the smallest standard service size and with your current service. Breaker ratings are not loads, which is why it does not simply add up the breakers.

Final panel assessments and upgrades belong in the hands of a licensed electrician, so treat these numbers as a starting point for that conversation. Where people most often go wrong is underestimating future demand, particularly the heavy dedicated circuits new EV chargers need, for example 50A for Level 2 charging.

Example: Before Adding an EV Charger

  1. 1 Enter the home: 2,000 sq ft, 3 small-appliance and laundry circuits, 17 kW of fixed appliances (range, dryer, water heater, dishwasher), a 5 kW air conditioner, no electric heat and a 200-amp service.
  2. 2 General load: 2,000 × 3 = 6,000 VA + 3 × 1,500 = 4,500 VA + 17,000 VA = 27,500 VA. After the demand factor: 10,000 + 40% × 17,500 = 17,000 VA. Adding the 5,000 VA air conditioner gives 22,000 VA, or 22,000 ÷ 240 = 92 amps: 108 amps of headroom on a 200-amp service.
  3. 3 Add a 48-amp Level 2 charger (11.5 kW): the general load rises to 39,000 VA, the demand load to 10,000 + 40% × 29,000 = 21,600 VA, and the total to 26,600 VA, 111 amps, still well inside 200 amps (a 100-amp service would not be enough; the smallest standard size that covers it is 125 amps).
  4. 4 This is a planning estimate. Before adding a large load, have a licensed electrician do the Article 220 load calculation for your code edition; a service upgrade needs a permit and inspection, and the utility may also need to upgrade the service drop.

Source: IAEI Magazine: Residential Service Calculations in the National Electrical Code (NEC Article 220) · Last updated: September 2026

Frequently Asked Questions

How do I know if my electrical panel needs an upgrade?
Signs include frequent breaker trips, flickering lights, a warm or discolored panel, or a fuse box instead of breakers. If you are adding an EV charger, hot tub, or major addition, have a licensed electrician run a load calculation first; it shows whether the existing service can carry the new load or needs a permitted upgrade. Panel size alone, such as having less than 200 amps, does not mean an upgrade is needed.
How much does an electrical panel upgrade cost?
This calculator shows rough ranges of $1,500-$2,500 for a 100-amp panel, $2,000-$3,500 for 150 amps and $2,500-$4,500 for 200 amps. Real prices, including the permit and inspection, vary by region and by whether the utility needs to upgrade the service drop to your home.
How do I calculate my total electrical load?
Not by adding up breaker ratings. The NEC Article 220 calculation starts with 3 volt-amperes per square foot of floor area for general lighting and receptacles, adds 1,500 volt-amperes for each small-appliance circuit and the laundry circuit plus the nameplate ratings of appliances such as the range, dryer and water heater, and then applies demand factors; the heating or air-conditioning load is handled separately. An electrician does this calculation before sizing or upgrading a service.

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