Electrical load calculator
Enter the floor area, appliances and heating and cooling equipment to get the calculated load and the service size, with every demand factor shown.
Inputs
Result
Heating and cooling options, 220.82(C)
Only the largest of these is added to the general load.
| Option | Load, VA |
|---|
How it works
The optional method in NEC 220.82 applies to a single dwelling unit served by a 120/240 V or 208Y/120 V three-wire service or feeder of 100 A or more. It adds two parts.
General loads, 220.82(B)
- 3 VA per square foot for general lighting and receptacles
- 1,500 VA for each 20 A small-appliance circuit and each laundry circuit
- The nameplate rating of every appliance fastened in place or on a dedicated circuit: range, dryer, water heater, dishwasher, EV charger and so on
The first 10,000 VA counts at 100% and the rest at 40%.
Heating and air conditioning, 220.82(C)
Add only the largest of: air conditioning at 100%; a heat pump without supplemental heat at 100%; a heat pump compressor at 100% plus supplemental heat at 65%; electric space heating at 65% for fewer than four separately controlled units, or 40% for four or more; thermal storage heating at 100%.
When to use a different method
The standard method in Article 220, Part III often gives a different answer and is the one to use for services under 100 A. Adding load to an existing home has its own optional method in 220.83, and 220.87 lets you use a year of measured peak demand instead of a calculation. Your utility and inspector may also have their own requirements.
Questions
Do I need a 200 amp service?
Only if the calculated load is over 150 A. A 2,000 ft² home with a range, dryer, water heater, dishwasher and central air typically comes to about 100 A under the optional method; electric heat, a heat pump with strip heat or an EV charger are what usually push a home past 150 A.
Can I add an EV charger to a 100 amp panel?
Sometimes. Add the charger's nameplate VA here to see the new calculated load. For an existing home, 220.83 and 220.87 can give a more accurate answer, and a load management device can let a charger share capacity.
What is the difference between VA and watts?
For resistive loads such as heaters and ranges they are equal. For motors, VA is slightly higher than watts. Load calculations use VA from the nameplate: volts × amps.
Why does the calculator only add one heating or cooling load?
Heating and cooling rarely run at the same time, so 220.82(C) adds only the largest of the options rather than all of them.
Which NEC edition does this follow?
The 220.82 method, demand factors and 3 VA per square foot used here are as published in the 2017 through 2023 editions. Check which edition your jurisdiction has adopted.
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