Major Appliances (watts)
HVAC (watts)
NEC uses the larger of heating or cooling.
EV charger, pool pump, hot tub, workshop, etc.
Your Results
Enter home details and click calculate.
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What This Calculator Does
This residential electrical load calculator estimates the total service amperage and panel size needed for a home using the 2026 National Electrical Code (NEC) Article 220 Standard Calculation method. It applies NEC demand factors to general lighting, small appliance circuits, and major appliances to determine the calculated demand load. The tool recommends service size (100A, 150A, 200A, or 400A) and provides a circuit breaker breakdown for panel layout planning.
The Formula
The NEC Standard Calculation starts with general lighting at 3 VA per square foot, plus two small appliance circuits (3,000 VA) and one laundry circuit (1,500 VA). A demand factor is applied: the first 3,000 VA at 100% and the remainder at 35%. Ranges up to 12 kW use an 8 kW demand per NEC Table 220.55. Dryers use the nameplate rating or 5,000 watts minimum per NEC 220.54. HVAC uses the larger of heating or cooling per NEC 220.60. The total demand in VA divided by the service voltage (typically 240V) gives the required amperage.
Step-by-Step Example
Enter home size
A 2,000 sq ft home has a general lighting load of 6,000 VA (2,000 x 3 VA/sq ft).
Enter major appliances
Range: 12,000W. Dryer: 5,500W. Water heater: 4,500W. Dishwasher: 1,500W.
Enter HVAC loads
AC: 5,000W. Electric heat: 10,000W. NEC uses the larger value: 10,000W.
Review service sizing
Total connected: 42,500 VA. After demand factors: approximately 35,700 VA. At 240V: 149 amps. Recommended: 200-amp service.
Real-World Use Cases
New Home Construction
Determine the correct service size and panel capacity during the design phase to avoid costly service upgrades later.
Service Upgrade Evaluation
Determine whether a homeowner adding an EV charger, hot tub, or workshop needs to upgrade from 100A to 200A service.
Permit Applications
Provide load calculations to support electrical permit applications required by most jurisdictions for new construction or service upgrades.
Common Mistakes to Avoid
Adding up all appliance nameplate ratings without applying NEC demand factors. The demand calculation accounts for the fact that not everything runs simultaneously.
Using the sum of heating and cooling loads. NEC 220.60 specifies using the larger of the two because they do not operate at the same time.
Forgetting future loads. If the homeowner plans to add an EV charger (7,200W to 11,500W), include it now to avoid a service upgrade later.
Not accounting for NEC Table 220.55 demand factors for ranges. A 12 kW range uses only 8 kW for load calculation purposes, not the full nameplate rating.
Frequently Asked Questions
Accuracy and Disclaimer
This calculator uses the NEC Article 220 Standard Calculation method for residential load estimation. Local jurisdictions may adopt amendments to the NEC that change requirements. This tool is for planning and estimation purposes. A licensed electrician must perform the official load calculation for permit applications. Always hire a licensed electrical contractor for installation work.
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