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Residential Electrical Load Calculator

Estimate residential service load using a floor-area minimum and entered major appliances. Verify the final result with the required code method before sizing service equipment.

Electrical Load Calculation

Square Footage

General Lighting (W)

Receptacles (W)

HVAC/AC (W)

Water Heater (W)

Electric Range (W)

Dryer (W)

Dishwasher (W)

Garage Door (W)

Service size is based on calculated demand load, not total connected watts

What is Electrical Load Calculation?

Connected load is every major load added together at nameplate value. Demand load applies reductions and assumptions so the service is not sized as if every load ran at full output at the same time. This page gives a simplified residential estimate, not a permit-ready Article 220 worksheet.

The estimate here uses a floor-area minimum, a reduced general-load demand above the first 3000 VA, and the entered major appliances. That is useful for rough sizing, but local code adoption, optional methods, and additional loads can change the final answer.

Connected vs. Demand (The Real Difference)

If you added every appliance's full power rating, the total would usually be much higher than the service actually needs to support under the calculation method. Demand factors and diversity assumptions are what make service sizing practical.

How the NEC Actually Calculates Demand

General load: Uses the larger of entered general load or 3 VA per square foot, then applies 100% to the first 3000 VA and 35% to the balance.
Heating or cooling: Uses the entered HVAC load at 100% as a simple stand-in for the larger noncoincident climate load.
Major appliances: Adds the entered water heater, dryer, dishwasher, garage load, and a reduced electric range value.
Important: This is a simplified estimate and does not replace a full Article 220 calculation.

Service Sizes and What They Support

Service Size	Max Amps	Max Power (kW)	Typical Home
60A	60	14.4	Very old or tiny homes
100A	100	24	Small house, 1200-2000 sqft
150A	150	36	Medium house, 2000-3500 sqft
200A	200	48	Large house, 3500+ sqft, electric heat
300A	300	72	Huge homes, all-electric, EV charging

When Your Service Needs an Upgrade

There is not a blanket NEC rule that a service must stay under 80% of its rating. Continuous loads and equipment ratings have their own rules, and leaving headroom is a design choice rather than a single universal service threshold. If you are close to the next standard service size, run a full load calculation instead of relying on a shortcut.

Frequently Asked Questions

Because service calculations do not assume every load runs at its nameplate value at the same time. General-use loads are reduced with demand factors, while major fixed loads are handled more directly.

Most codes require minimum 100A, with 200A common for newer or larger homes. All-electric homes usually need 200A. Local code has the final say.

Absolutely not. Licensed electrician only. Utility coordination required. Permits required. One mistake and you're looking at electrocution or fire. This isn't a DIY job.

A Level 2 charger can add a large continuous load. This simplified page does not include a dedicated EV charger input, so add that load manually and verify the final service calculation with the required code method.

Not as a blanket rule for service calculations. The NEC handles continuous loads, demand factors, and equipment ratings in specific sections. Leaving spare capacity is good practice, but it is not the same thing as a universal 80% service cap.