Electrical Load Calculator
Calculate your home's total electrical load using the NEC Article 220 method. Find out if your panel can handle your loads and what service size you need.
How to Use This Calculator
- Enter your home's square footage — this determines the baseline general lighting load at 3 VA/sq ft per NEC requirements.
- Set the number of small appliance circuits — NEC requires a minimum of two 20A circuits for kitchen countertops. Add more if applicable.
- Enter your large appliance wattages — use the nameplate rating or typical wattages. Set any gas or absent appliances to 0.
- Select your current panel size — the calculator will tell you if it's adequate or if you need an upgrade.
NEC Article 220 Load Calculation Method
- Step 1 — General Load:
General Load VA = Square Footage × 3 - Step 2 — Small Appliance & Laundry:
SA Load = (Small Appliance Circuits × 1,500) + (Laundry Circuits × 1,500) - Step 3 — Apply Demand Factor:
Demand VA = 3,000 + ((Subtotal − 3,000) × 0.35) - Step 4 — Add Large Appliances:
Total VA = Demand VA + HVAC + Water Heater + Dryer + Range + Other - Step 5 — Service Amperage:
Service Amps = Total VA ÷ 240
The demand factor reduces the general load because not all circuits run simultaneously at full capacity. Large fixed appliances (HVAC, water heater, dryer, range) are added at 100% because they are dedicated circuits that can run at full rated load.
Pro Tips
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Panels & Tools
Square D 200A Main Panel
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View on Amazon →Frequently Asked Questions
What is the NEC method for calculating home electrical load?
NEC Article 220 defines the standard calculation method. It starts with 3 VA per square foot for general lighting, adds 1,500 VA per small appliance circuit (minimum two required in kitchens), applies a demand factor to the subtotal (first 3,000 VA at 100%, remainder at 35%), then adds large appliances at 100%. The total VA divided by 240V gives the required service amperage.
How do I know if my panel is too small?
Signs of an undersized panel include breakers that trip frequently, flickering lights when appliances start, inability to add new circuits, or a calculated load that exceeds 80% of your panel's rating. A 100A panel supports about 24,000 VA. If your calculated load approaches or exceeds this, a panel upgrade is warranted.
Does this calculator account for all NEC load types?
This calculator uses a simplified version of the NEC Article 220 standard load calculation method, suitable for estimating residential service size. A licensed electrician performing a permit-required calculation must use the full NEC method, which includes additional considerations for electric heat, air conditioning, motor loads, and optional demand factors.
What size panel do most new homes need?
Most new construction homes today are built with 200A service panels, which is sufficient for typical loads including central HVAC, electric appliances, and general use. Homes with electric vehicle chargers, large shops, pool equipment, or multiple HVAC zones may require 400A service or a subpanel arrangement.