Electrical Load Calculator
Estimate the demand load and recommended service size for a panel upgrade — built for electricians sizing residential services before pulling a permit.
Building
Service size
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Please add: Square footage, Small-appliance circuits, Laundry circuits, HVAC load, Water heater, Range, Dryer.
Size the service
Build With UsThe Electrical Load Calculator estimates a home's total electrical demand from its square footage, circuits, and major appliances, using the NEC 220.82 optional method for a dwelling.
Getting the demand right is the step before sizing a service. A good estimate points you at the right panel, keeps circuits off the edge of overload, and leaves room for what gets added later.
How to Use the Electrical Load Calculator
Start with the building's square footage — the finished, habitable floor area. NEC 220.12 assigns a general lighting and receptacle load of 3 VA per square foot, so this is a major input. Garages, open porches, and unfinished space don't count.
Next, the number of small-appliance circuits and laundry circuits, each counted at 1,500 VA per NEC 220.52.
Then the major appliances — HVAC, water heater, range, dryer — plus an optional EV charger and any other fixed appliances (dishwasher, microwave, disposal). Enter these at nameplate watts.
The calculator sums the general and appliance loads, applies the 220.82(C) demand factor (the first 10,000 VA at 100%, the rest at 40%), adds the HVAC load and the EV charger — the latter at 125% as a continuous load — and divides by 240V to get amps. It then recommends the smallest standard service that covers the result.
Electrical Load Calculator Example
A new 2,200 sq ft home with:
- Two small-appliance circuits and one laundry circuit
- 4-ton AC (a 5,760 VA / 24 A nameplate draw)
- 4,500 VA electric water heater
- 8,000 VA electric range
- 5,000 VA electric dryer
- 2,700 VA of other fixed appliances (dishwasher plus microwave)
- 7,200 VA Level 2 EV charger
Step 1: General and lumped loads. General lighting is 3 VA × 2,200 = 6,600 VA. Add the small-appliance circuits (2 × 1,500 = 3,000), the laundry circuit (1,500), the range (8,000), the dryer (5,000), the water heater (4,500), and the other fixed appliances (2,700). That's 31,300 VA before the demand factor.
Step 2: Apply the 220.82(C) demand factor. The first 10,000 VA counts at 100%; the remaining 21,300 at 40%. So 10,000 + 21,300 × 0.40 = 18,520 VA.
Step 3: Add HVAC and the EV charger. The 4-ton AC adds its full 5,760 VA. The EV charger is a continuous load, added at 125%: 7,200 × 1.25 = 9,000 VA. Total demand = 18,520 + 5,760 + 9,000 = 33,280 VA.
Step 4: Convert to amps and pick a service. 33,280 ÷ 240 = ≈139 amps, so a 150-amp service covers it with room to spare.
The optional method is deliberately less conservative than a full standard calculation, because it recognizes that not every load runs at once. A standard calculation on the same appliances lands higher and might point you at a 200-amp service — which is why this is a planning estimate, not a substitute for the full calculation on the permit.
Why Electrical Load Calculations Matter
A proper load calculation prevents overloaded circuits, nuisance breaker trips, and overheating conductors, and confirms there's capacity for future appliances, additions, or EV charging.
The calculator gives a fast, defensible estimate to plan from before you install or upgrade a service.
Typical appliance nameplate loads
Rough nameplate wattages if you don't have the appliance data plate handy:
Frequently Asked Questions
Is this a full NEC load calculation?
No. It's a simplified version of the NEC 220.82 optional calculation for a dwelling. A full calculation accounts for every circuit, jurisdiction-specific demand factors, and any local amendments.
Why is the load reduced above 10,000 VA?
NEC 220.82(C) recognizes that not every circuit runs at full load at once. The first 10 kVA of the combined general and appliance load counts at 100%, and the remainder at 40%.
Why does the EV charger get a 125% factor?
EV charging is a continuous load under NEC 210.19(A), which requires the circuit and demand to be sized at 125% of the equipment's continuous rating.
Can the Electrical Load Calculator replace a professional load calculation?
No. It's a reliable planning estimate, but the calculation on the permit belongs to a licensed electrician or engineer working from the full NEC and local code.
This is a simplified planning estimate based on the NEC 220.82 optional method, not a substitute for a full load calculation performed by a licensed electrician. Verify service sizing against local code and your authority having jurisdiction before installing or upgrading equipment.
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