Electrical Load Calculator
This electrical load calculator estimates the service size a house needs, using the NEC 220.82 optional method for a single dwelling. Enter the living area, the kitchen and laundry circuits, the nameplate rating of fixed appliances, and the larger of the heating or cooling load, and the electrical load calculator returns the demand load in VA, the current in amps, and a suggested standard service size.
Preliminary estimate for one dwelling. Have a licensed electrician confirm the service size.
Results
The Electrical Load Calculator is part of our Cable & Protection collection. Browse more cable & protection to size, convert, and check your work alongside this tool.
What the electrical load calculator does
Not every appliance in a house runs at full power at the same time, so codes allow a demand factor. The NEC optional method for one dwelling counts the general load at 100% for the first 10 kVA and 40% for the rest, then adds the larger of the heating or air conditioning load. The electrical load calculator follows that method and divides by the service voltage to give amps.
NEC load calculation method
The general load adds:
The first 10,000 VA counts in full and the rest at 40%. Then the heating or cooling load is added at 100%:
This simplified version takes the HVAC load as entered; the full 220.82(C) rules apply different factors to some electric heating arrangements.
Electrical load calculator example
A 2,000 sq ft house with two kitchen circuits, one laundry circuit, 22,500 VA of appliances, and a 5,000 VA air conditioner on 240 V:
24,200 ÷ 240 = 100.8 A, so the next standard size is a 125 A service. Many homes choose 200 A to leave room for an EV charger or heat pump.
How to use the residential load calculation tool
Enter the heated living area in square feet. Keep at least two kitchen small appliance circuits and one laundry circuit. Add up the nameplate VA or watts of fixed appliances: range, oven, cooktop, dryer, water heater, dishwasher, disposal, microwave, and any EV charger. Enter the larger of the heating or cooling load and the service voltage, then press Calculate.
Reading your electrical service size result
The calculated amps are the minimum the service must carry. Pick the next standard size and allow for future loads: an EV charger alone can add 7,680 VA on a 32 A circuit. If the result is close to your existing panel rating, a load study or an energy management device may avoid an upgrade. A licensed electrician and your local inspector make the final call.
When to use a house electrical load calculator
- Checking whether a panel can take an EV charger
- Planning a service upgrade before a remodel
- Sizing service for a new home
- Adding a heat pump or electric range
- Preparing a load calculation worksheet for a permit
Common electrical load calculator mistakes
- Adding heating and cooling together. Use the larger one.
- Using breaker sizes as loads. Use nameplate VA.
- Forgetting future loads. Plan for an EV charger or heat pump.
- Using this for apartment buildings. Multifamily uses other methods.
Tips for a house electrical load calculation
- Photograph appliance nameplates as you go.
- Use the outdoor unit nameplate for air conditioners.
- Ask your utility about service upgrade lead times.
Residential load calculation step by step
List the area first, since lighting and receptacles are covered by the 3 VA per square foot allowance. Each kitchen small appliance circuit and laundry circuit counts as 1,500 VA. Then add every fastened-in-place appliance at its nameplate rating. Apply the demand factor, add heating or cooling, and divide by the voltage. Each branch circuit in the house still needs its own breaker and wire, which the breaker size calculator and the wire size calculator size from the load.
200 amp service calculator: when to upgrade
A 100 A service often runs short once a house adds central air, an electric range, and an EV charger. Rerun the calculation with the new loads. If the total passes about 150 A, 200 A is the usual next step. For homes that need backup power, the same load list helps size a standby unit with the generator size calculator, covering only the essential circuits.
Load calculation worksheet: typical appliance ratings
Use the nameplate when you have it; these are common values:
| Appliance | Typical VA |
|---|---|
| Electric range | 8,000 to 12,000 |
| Electric dryer | 5,000 to 5,500 |
| Water heater | 4,500 |
| Dishwasher | 1,200 |
| Garbage disposal | 900 |
| Microwave | 1,500 |
| Level 2 EV charger, 32 A | 7,680 |
| Level 2 EV charger, 48 A | 11,520 |
Electrical Load Calculator FAQ
How many amps does my house need?
Run the load calculation. The example 2,000 sq ft house needs about 101 A, so a 125 A service; most new homes use 200 A.
What is the NEC 220.82 optional method?
A simplified load calculation for one dwelling: 100% of the first 10 kVA of general load, 40% of the rest, plus the heating or cooling load.
Can I add an EV charger to a 100 A panel?
Sometimes. Add the charger to the load calculation; if the result exceeds the panel rating, consider a load management device or an upgrade.
Is this enough for a permit?
It is a good estimate, but the inspector may require the full NEC worksheet and local amendments.