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Panel Load Calculator

Calculates total demand load for service entrance sizing per NEC Article 220 demand factors. Residential and commercial.

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Load Breakdown

Total Demand Load --

Based on NEC Article 220 demand factors for single-family residential. This is an estimate — consult a licensed engineer for final service design.

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How to Use This Calculator

1. Enter your home square footage. The calculator uses 3 VA per square foot for general lighting load per NEC 220.12.

2. Select your heating type and cooling size. The calculator uses the larger of heating or cooling load — NEC assumes they do not run simultaneously.

3. Check off major appliances. Electric range, dryer, water heater, and EV charger each add significant load. Gas appliances do not contribute to the electrical demand.

4. Review the results. The calculator applies NEC Article 220 demand factors and recommends the nearest standard service size.

NEC Article 220 Demand Factors

The NEC does not require you to size service for 100% of all connected loads running simultaneously. Demand factors reduce the calculated load to a realistic peak demand.

General Lighting: First 3,000 VA at 100%, remainder at 35%

Small Appliance + Laundry: 4,500 VA with same demand factor

Range (Table 220.55): 8 kW demand = 8,000 VA

Dryer: 5,000 VA (or nameplate if larger)

Water Heater: Full nameplate VA

HVAC: Larger of heating or cooling at 100%

EV Charger: Full nameplate VA

Service Amps = Total Demand VA / 240V

Frequently Asked Questions

How do you calculate panel load per NEC Article 220?
NEC Article 220 uses demand factors to reduce the total connected load to a realistic demand. General lighting is 3 VA per square foot with a demand factor of 100% on the first 3000 VA and 35% on the remainder. Small appliance and laundry circuits add 4500 VA with the same demand factor. Individual loads like range, dryer, water heater, and HVAC are added at nameplate or demand values from NEC tables.
What size electrical service do I need for my house?
Most modern homes require 200A service. NEC 230.79 sets the minimum at 100A for single-family homes. Calculate total demand load per Article 220, divide by 240V, and round up to the next standard breaker size.
Do I use the larger of heating or cooling load?
Yes. NEC assumes heating and cooling are not used simultaneously, so you include only the larger of the two loads in your demand calculation.

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