Calculate residential electrical service size per NEC optional method. Compare NEC 2026 vs 2023, see the complete demand factor breakdown, and determine your recommended service size.
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Only the larger of heating or cooling is used — they are non-coincident loads.
NEC 220.82 (2023) / 120.82 (2026) provides a simplified calculation for single-family dwellings. Instead of applying individual demand factors to each load category, it sums all general loads, applies a blanket demand factor (first portion at 100%, remainder at 40%), then adds HVAC at 100%. This typically yields a smaller service size than the standard method.
NEC 2026 restructured Article 220 into Article 120 and reduced general lighting from 3 VA/sq ft to 2 VA/sq ft — reflecting modern LED lighting efficiency. The 100% demand threshold also dropped from 10,000 VA to 8,000 VA. For many homes, these changes offset each other, but larger homes see a net reduction in calculated load.
Heating and cooling loads are non-coincident — you only use the larger of the two because both systems never run simultaneously. The HVAC load is added at 100% demand, outside the 40% reduction applied to general loads. This is why HVAC often dominates the service sizing calculation.
A Level 2 EV charger at 240V × 32A adds 7,680 VA to the load calculation. While subject to the 40% demand reduction on the portion above the threshold, EV charging is still the single largest load addition most homeowners make. It frequently pushes a 150A service to 200A. NEC 2026 added specific EV charging provisions in Article 625.