Electrical Load Calculator
Amps, watts & circuit sizing
Enter service details
Sum of range, dryer, AC, EV charger, etc.
Your results
Enter your project details to see results.
Formula & explanation
This follows the NEC standard method: 3 watts per square foot for general lighting and receptacles, plus two 1,500W small-appliance circuits and one 1,500W laundry circuit (6,000W total). The demand factor applies 100% to the first 8,000W and 40% to the remainder (NEC 220.42). Divide by 240V (most service) to get amps; round up to the next standard service size.
Example calculation
2,000 sq ft home, 12,000W of major appliances:
Lighting = 2,000×3 = 6,000W + 6,000W + 12,000W = 24,000W. Demand = 8,000 + 0.4×16,000 = 14,400W ÷ 240V = 60A → suggest a 100A service (200A with EV/heat pump loads).
Buying & project-planning tips
- Electric ranges, dryers, water heaters, and EV chargers each need their own dedicated circuits.
- Heat pumps and EV chargers often push older 100A homes to need a 200A service upgrade.
- Modern homes with electric everything often need 200A or even 400A service — don't assume 100A is enough.
- GFCI/AFCI protection is required per the latest NEC for most indoor and outdoor circuits.
- Any service change or new circuit requires a permit and inspection by your local authority.
Frequently asked questions
How do I size my electrical service?+
The NEC standard method (shown here) sums lighting, receptacles, and appliance loads, then applies demand factors. For new construction or major additions, a licensed electrician performs the full Article 220 calculation and sizes the panel accordingly.
Is 100 amp service enough for a modern home?+
It was standard for decades but may be tight today. Homes with electric heat, AC, an EV charger, or a large kitchen often need 200A. A load calculation tells you for sure.
Does this calculator prove my wiring is safe?+
No — this is a planning estimate. Actual safety depends on wire sizing, breaker coordination, grounding, and code-compliant installation verified by a licensed electrician and inspector.
Do I need a permit for an electrical upgrade?+
Yes — any service change, panel upgrade, or new circuit almost always requires a permit and inspection. Work done without permits can void insurance and create safety hazards.
Safety notice: This electrical load estimate does not certify that any installation is safe. Electrical service and circuit sizing must be performed by a licensed electrician per the NEC and local code. Undersized wiring is a fire hazard.