Before you commit to a new electric range or other major kitchen appliance, you can answer the capacity question yourself with a standard National Electrical Code (NEC) load calculation. The method, laid out in NEC Article 220, converts your home's square footage, required circuits, and appliance nameplate ratings into a single amperage figure you can compare against your service panel's rating. In the worked example below, a hypothetical 2,000-square-foot home with a new range works out to roughly 81 amps of calculated demand—comfortably within a 100-amp service, though your own numbers may differ.
Understanding Residential Electrical Load Calculations
A load calculation is the formal procedure electricians use to size a home's service, feeders, and branch circuits safely. NEC Article 220 is the primary source for these methods, and it has governed safe component sizing since the code's early editions in the late 19th century. The calculation matters because a panel that is undersized for the loads attached to it invites overloaded conductors and tripped—or worse, failed—overcurrent protection.
Some jurisdictions make the calculation a formal requirement. Centerville, Indiana's municipal code, for example, requires an electrician applying for an inspection permit to submit service load calculations alongside an architectural-electrical plan, and it codifies the specific NEC values: three watts per square foot for general lighting, 1,500 watts for each of the two required small appliance circuits, and 1,500 watts for the laundry circuit. This article covers the standard method for single-family dwellings only—not the optional method, and not multi-family or commercial properties. All electrical work should be done by a qualified electrician and must comply with local codes, which vary.
What Are NEC Demand Factors and Why They Matter
The single most common mistake in load calculations is adding up every nameplate rating at full value. The NEC doesn't require that, because the code recognizes that not everything in a house runs at full power simultaneously. A demand factor is a percentage the code lets you apply to a group of loads to reflect realistic, non-simultaneous use.
Two demand factors do most of the work in a residential calculation. First, for the combined general lighting, small appliance, and laundry loads, NEC Table 220.42 counts the first 3,000 VA at 100% but only 35% of everything beyond that. Second, for fixed appliances, when a dwelling has four or more of them, the code permits a 75% demand factor on their combined nameplate load. Cooking equipment gets its own treatment: under Table 220.55, one household range rated up to 12 kW can be counted at just 8 kW. As electrical exam-prep materials and electrician guides explain, these reductions are why a house full of appliances rarely needs a service as large as raw nameplate totals would suggest.
