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Electrical Load Calculator

Enter your home's area, lighting load and appliance load to size the panel.

How it is calculated

The tool adds a lighting-type load based on floor area to the appliance load you supply, then divides by the service voltage. The steps are general load = area × VA per sq ft, total VA = general load + appliance VA and current = total VA ÷ voltage. Area is in square feet, the density is in volt-amperes per square foot, appliances are the combined VA of the equipment you list, and voltage is the service voltage (for example 240). The current is simply the total divided by the voltage, as for a single-phase service. The calculation is a simplified sum: it applies no demand factors, adds no fixed allowances for small-appliance or laundry circuits, and does not handle three-phase or add safety margins. The voltage must be above zero.

Worked example

A home has 1,800 sq ft of floor area and a lighting density of 3 VA per sq ft, so the general load is 1,800 × 3 = 5,400 VA. The appliances you list add up to 11,500 VA, so the total load is 5,400 + 11,500 = 16,900 VA. On a 240 V service, the current is 16,900 ÷ 240 = 70.42 A. That figure fits within a 100 A service on paper, though the actual panel rating should be chosen by a qualified electrician applying the local code.

Try this example →

Common mistakes

  • Entering appliance loads in kilowatts. The appliance field is a total in VA, so add up the nameplate figures first and convert kW to VA by multiplying by 1,000.
  • Using the area in square metres. The field expects square feet; 150 m² is about 1,615 sq ft.
  • Forgetting to add large fixed loads such as a range, dryer, water heater or air conditioner. The tool only adds what you enter in the appliance field.
  • Treating the result as the final panel size. It has no demand factors, no allowance for future circuits and no code margin, so it is an estimate for planning.
  • Mixing voltages. Using 120 instead of 240 for a 240 V service doubles the current figure.

About this calculator

Sizing a home's electrical service starts from the logic of the NEC dwelling load calculation: general lighting load is figured per square foot of living area (the NEC uses 3 VA per square foot), and the appliance loads are added on top. Dividing the resulting total VA by the service voltage gives the required amperage. This is a simplified version: you enter the VA per square foot and the total appliance VA yourself, and no demand factors are applied, so the result is a conservative estimate that treats everything as running at once; the full NEC standard method also adds fixed allowances for small-appliance and laundry circuits and applies demand factors.

This calculator takes a home's floor area in square feet, the VA per square foot, the total appliance VA and the service voltage, and returns the total electrical load and service current. Electricians use this calculation to get a first idea of whether an existing panel (commonly 100A or 200A) has enough capacity for a renovation or new appliance circuit, and home inspectors and electrical engineers use it as a quick check before the full code calculation that a service upgrade permit requires.

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