Electrical Panel Load Calculator
The National Electrical Code (NEC) Article 220 specifies how to calculate the total electrical demand of a residence to size the service entrance and main panel. The simplified approach sums general lighting load (3 VA per square foot), mandatory small-appliance and laundry branch circuits, fixed appliances at nameplate rating, and the larger of heating or cooling load. The NEC then applies demand factors: for general lighting, only the first 3,000 VA is counted at 100%, with the remainder at 35%. The total in VA divided by 240 V gives the required service amperage.
NEC residential load calculation (simplified)
Lighting VA = sq ft × 3
Demand lighting = first 3,000 VA @ 100% + remainder @ 35%
Small appliance VA = circuits × 1,500 VA (demand: first 3,000 @ 100%, rest @ 35%)
Laundry circuit = 1,500 VA @ 100%
HVAC = larger of heating or cooling nameplate
Dryer (NEC 220.54) = 5,000 VA or nameplate, whichever is larger
Range (NEC 220.55) = 8,000 VA demand for single unit
Total VA = sum of all above
Service amps = Total VA ÷ 240
This calculator implements the simplified optional calculation from NEC 220. Demand factors for lighting and small-appliance circuits are applied as specified. Range demand is capped at 8,000 VA per NEC Table 220.55 Column C for a single range. Always verify with a licensed electrician before ordering equipment.
Panel sizing guidelines
- 100A service (minimum for new residential) handles homes up to about 1,200 sq ft without electric heat.
- 200A service is standard for most modern single-family homes and supports central AC, electric range, and dryer.
- 400A service is required for homes with electric vehicle chargers, electric heat, and large workshops or pools.
- Panel breaker slots should not be filled to capacity; leave 20-25% spare capacity for future loads.
- A full NEC Article 220 standard method calculation is required for commercial and multi-family occupancies.
Electrical panel load: frequently asked questions
How do I calculate my home's electrical load?
NEC Article 220 provides two methods: the standard method (detailed, used by engineers) and the optional method (simplified). For a residence, start with general lighting load at 3 VA per square foot, add small appliance branch circuits (1,500 VA each, minimum two), a laundry circuit (1,500 VA), then add fixed appliances and HVAC loads. Apply demand factors where allowed.
What size electrical service do I need for a house?
Modern single-family homes typically need 100 to 200 amp service. A 100A service handles smaller homes without electric heat or large EV chargers. 200A is the current standard for new construction and most upgrades. Homes with electric vehicle chargers, electric heating, or large pools or workshops may need 400A.
What is demand factor and why is it applied?
Demand factor accounts for the reality that not all loads run simultaneously at full rated capacity. The NEC allows a 35% demand factor on the general lighting load above the first 3,000 VA. Large appliances like clothes dryers and ranges get specific demand factors based on the number of units.
Do I need to include my EV charger in the load calculation?
Yes. A Level 2 EV charger (240V, 32A) adds 7,680 VA (32A x 240V) to the service load. NEC 625.42 allows some demand factor reductions when a demand management system is installed, but for standard load calculation purposes, use the full charger rating.
Can I do this calculation myself or do I need an electrician?
The load calculation can be done by a homeowner for planning purposes, but any actual panel upgrade or service entrance work must be permitted and inspected. In most jurisdictions, residential electrical work beyond basic replacements must be done by a licensed electrician.
Official sources
- NFPA 70 (NEC): National Electrical Code Article 220.
- U.S. DOE: Home Electrical Systems.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.