Electrical Panel Load Calculator
Estimate the minimum service amperage your home's electrical panel needs based on lighting, kitchen appliances, and HVAC loads. Use this before upgrading a panel or planning a new home build.
Last updated: September 2026
Formula below · 2 sources (nfpa.org, Wikipedia) · Updated Sep 2026
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About this calculator
This calculator follows the NEC 220.82 optional load calculation for a single-family dwelling. General loads (lighting and receptacles, which the NEC sets at 3 VA per square foot plus 1,500 VA for each small-appliance and laundry circuit, and the nameplate rating of kitchen and other fastened-in-place appliances) are added together; the first 10,000 VA counts at 100% and the remainder at 40%. Heating and air-conditioning are added at 100% (the NEC permits some electric heat at 65% or 40%, so 100% is the conservative choice). The formula is: required amps = ceil((min(G + K, 10,000) + 0.4 × max(0, G + K − 10,000) + HVAC) / 240), where G is general lighting and outlets and K is kitchen appliances. Dividing by 240 converts volt-amperes to amperes on a 120/240 V single-phase service. The service must be rated at least this value, and NEC 230.79(C) requires at least 100 A for a one-family dwelling. Typical residential services are 100 A, 150 A, or 200 A. A licensed electrician should do the formal NEC Article 220 calculation.
How to use
Example: general lighting and outlets = 8,000 W, kitchen appliances = 4,500 W, HVAC = 5,000 W. Step 1 — general loads: 8,000 + 4,500 = 12,500 VA. Step 2 — first 10,000 VA at 100% plus the remaining 2,500 VA at 40%: 10,000 + 1,000 = 11,000 VA. Step 3 — add HVAC at 100%: 11,000 + 5,000 = 16,000 VA. Step 4 — convert to amps at 240 V and round up: 16,000 / 240 = 66.67, so 67 A. The NEC minimum for a one-family dwelling is 100 A, so a 100 A service would satisfy this load. The defaults (3,000 + 4,500 general, 6,000 HVAC) give 7,500 + 6,000 = 13,500 VA, or 57 A.
Frequently asked questions
Why is only 75% of the general lighting load used in the panel calculation?
The NEC 220.82 optional method recognizes that not every light, outlet and appliance runs at the same time: it counts the first 10,000 VA of general loads at 100% and everything above that at 40%. Heating and air-conditioning are counted at 100%, because they run together for long periods in peak weather. The older NEC standard method uses different factors (for example 3,000 VA at 100% and the next 117,000 VA at 35% for general lighting), but both are code methods; a flat 75% factor is not.
What size electrical panel does a modern home typically need?
Most new single-family homes are built with 200 A service, which accommodates typical loads plus electric vehicles, heat pumps, and other high-draw modern appliances. Older homes built before the 1980s often have 60 A or 100 A panels that may need upgrading if you add central air conditioning, an EV charger, or an electric range. A licensed electrician should perform a full NEC load calculation before specifying panel size, as local codes may impose additional requirements.
When should I upgrade my home's electrical panel?
Common triggers for a panel upgrade include frequently tripping breakers, adding a major appliance like a hot tub or EV charger, finishing a basement or garage, or buying an older home with a fuse box. If your calculated load exceeds your current panel's ampere rating, an upgrade is necessary for safety. Panels also have a service life of roughly 25–40 years; older panels from certain manufacturers have known defect histories and may warrant replacement on safety grounds alone. Always consult a licensed electrician for the final assessment.
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Sources & references
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