Demand Factor Calculator

The Demand Factor Calculator estimates your home's total electrical demand load using NEC 2023 standards — the code electricians and inspectors use to size a residential service panel correctly. Enter your total living area, small appliance circuits, laundry circuits, and major appliance ratings (electric range, dryer, HVAC, water heater, and more) to get your Total Demand Load in VA. Secondary outputs include General Load, General Load Demand, Appliance Load, and a Recommended Service Size in amps.

sq ft

Enter total living area in square feet. 3VA/sq ft as per NEC 2023

circuits

Minimum of 2 circuits required (1500VA each) per NEC 2023

circuits

Enter number of laundry circuits (1500VA each)

VA

Enter VA from nameplate rating. Standard value is 8000VA

VA

Enter VA from nameplate rating. Standard value is 5000VA

units

Enter the number of separate heating/cooling systems

VA

Enter VA rating for each HVAC unit

VA

900VA load

1200VA load

1500VA load

7200VA load

fans

250VA each

Results

Total Demand Load

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General Load

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General Load Demand

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Appliance Load

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Recommended Service Size

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Frequently Asked Questions

What is a demand factor in electrical calculations?

A demand factor is a multiplier applied to electrical loads to account for the fact that not all loads operate simultaneously at full capacity. It helps determine the actual electrical demand rather than the connected load.

How is the general load calculated for residential properties?

General load is calculated at 3VA per square foot of living area, plus 1500VA for each small appliance circuit (minimum 2), plus 1500VA for each laundry circuit, according to NEC requirements.

What demand factors apply to general lighting and receptacle loads?

The first 3000VA is at 100%, the next 117,000VA (3001-120,000VA) is at 35%, and any amount over 120,000VA is at 25%, per NEC Table 220.42.

How are major appliances factored into demand calculations?

Major appliances like ranges, dryers, and ovens have specific demand factors. Electric ranges use NEC Table 220.55, while other appliances are typically calculated at 100% of their nameplate rating.

What service size should I choose based on the demand calculation?

The service ampacity should be at least 100A for residential properties. Common sizes are 100A, 125A, 150A, and 200A. Choose the next standard size above your calculated demand load divided by 240V.

Are HVAC loads included at 100% in demand calculations?

HVAC loads are typically included at 100% of their nameplate rating, but only the larger of heating or air conditioning is counted since they don't operate simultaneously.

Why don't we add up all connected loads for service sizing?

Adding all connected loads would result in oversized electrical services. Demand factors account for diversity in load usage - not all electrical devices operate at maximum capacity simultaneously.