Residential Electrical Load Calculator
This calculator follows the standard residential calculation pattern: general lighting at 3 VA per square foot, small appliance and laundry branch circuits, fixed appliances, range and dryer, and the larger of heating or air conditioning — with the usual demand factor applied. Always verify against the code edition your jurisdiction enforces.
Dwelling Loads
General lighting at 3 VA per square foot.
1500 VA each, minimum two.
1500 VA each.
Dishwasher, disposal, microwave, EV charger.
Only the larger of heating or cooling is counted.
General lighting load
6,600 VA
Total before demand factor
31,500 VA
After demand factor
18,600 VA
100% of first 10,000 VA, 40% of remainder
Largest HVAC load
9,600 VA
Total calculated load
28,200 VA
Current at 240V
117.5 A
Suggested service size
125 A
6% spare capacity
Reading The Result Before You Quote
The most valuable output here is spare capacity. A house calculating at 158 amps on a 200 amp service has room for an EV charger or a heat pump; one calculating at 191 amps does not, and that changes the conversation from a simple install into a service upgrade with a utility coordination step.
Run the calculation twice when a customer is considering electrification: once as the house sits, once with the new load added. The second number is what determines whether the job is a two-hour install or a two-day project.
Where Estimates Go Wrong
Nameplate ratings, not assumptions. A tankless electric water heater or a 48 amp EV charger will move this calculation far more than the square footage will, and both are routinely left out of a quick mental estimate at the panel.
Estimating aid only. Verify every calculation against the National Electrical Code edition and local amendments adopted in your jurisdiction. Work must be performed and certified by a qualified licensed electrician.
Frequently Asked Questions
- What method does this calculator use?
- The standard dwelling calculation: 3 VA per square foot for general lighting and receptacles, 1500 VA per small appliance branch circuit, 1500 VA for laundry, nameplate ratings for fixed appliances, then the usual demand factor of 100 percent on the first 10,000 VA and 40 percent on the remainder, with heating or air conditioning added at the larger of the two.
- Why is only the larger of heating or cooling counted?
- Because they are non-coincident loads: a house does not heat and cool at the same time, so the calculation includes whichever is greater rather than both.
- What service size does the result point to?
- Divide total VA by 240 to get amps, then choose the next standard service size above it — commonly 100, 125, 150, 200, 320, or 400 amps. Panel and conductor selection also depends on conductor material, temperature rating, and ambient conditions.
- Can I use this for a permit or an inspection?
- No. It is an estimating aid. Submitted calculations must follow the code edition and amendments your jurisdiction has adopted and be prepared by a qualified licensed person.
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