What demand factor applies to general lighting load?

Under NEC 220.42, the first 3,000 VA of general lighting and receptacle load is taken at 100%, and the remainder up to 120,000 VA at 35% for dwellings.

Do I add air conditioning and heating loads together?

No. NEC 220.60 lets you omit the smaller of two non-coincident loads (heating vs air conditioning), since they don't run at the same time. Use the larger of the two.

When can I apply the 75% appliance demand factor?

NEC 220.53 permits a 75% demand factor when four or more fixed appliances (other than range, dryer, HVAC and space-heating) are on the same feeder or service.

What service size do I need for a typical home?

Most modern single-family homes calculate out to a 150 A or 200 A service. Larger homes with electric heat, EV charging or a workshop may require 200 A or more.

Electrical Load Calculator (NEC Article 220)

NEC

Calculate the total demand load and recommended service size for a panel. Add lighting, appliance, HVAC and other loads, and the calculator applies NEC Article 220 demand factors to return the demand current in amps and the next standard service size.

Service voltage (V)

Loads

Total demand

17.58kVA

Demand current

73.2A

Service size

100A

A 100 A service covers this load

General load after 220.42 demand factor: 4575 VA · Appliance demand: 0 VA · Largest HVAC: 5000 VA.

Simplified NEC Article 220 standard method. Optional and feeder/sub-panel methods are available in the Voltix app.

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How the load calculation works

NEC Article 220 doesn't simply add up every nameplate watt - it applies demand factors that reflect the fact that not every load runs at full power simultaneously. This calculator uses the standard method:

General loads (lighting, receptacles, small-appliance and laundry circuits) get the 220.42 demand factor.
Fixed appliances are taken at 75% when four or more are present (220.53).
Heating and air conditioning - only the larger of the two is counted (220.60).
Other loads such as ranges and EV chargers are added at 100% (real ranges have their own column factors in the app).

From VA to service size

Demand current = total demand VA ÷ service voltage. The result is rounded up to the next standard service size: 100, 125, 150, 200, 225, 300 or 400 A.

Frequently Asked Questions

What demand factor applies to general lighting load?: Under NEC 220.42, the first 3,000 VA of general lighting and receptacle load is taken at 100%, and the remainder up to 120,000 VA at 35% for dwellings.
Do I add air conditioning and heating loads together?: No. NEC 220.60 lets you omit the smaller of two non-coincident loads (heating vs air conditioning), since they don't run at the same time. Use the larger of the two.
When can I apply the 75% appliance demand factor?: NEC 220.53 permits a 75% demand factor when four or more fixed appliances (other than range, dryer, HVAC and space-heating) are on the same feeder or service.
What service size do I need for a typical home?: Most modern single-family homes calculate out to a 150 A or 200 A service. Larger homes with electric heat, EV charging or a workshop may require 200 A or more.

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