How it works & the NEC rules behind it
Homeowners electrifying their homes (replacing gas furnaces with heat pumps, adding Level 2 EV chargers, and switching to induction cooking) often face costly $4,000–$8,000 utility panel upgrades. NEC 2026 Article 120.83 (formerly Article 220.83) and §120.87 provide the legal calculation path to determine if your existing panel has room.
How Electrification Sizing Works:
- 1. Baseline Existing Demand (§120.87): Sourced from the highest peak 15-minute kW demand reading from the past 12 months of utility smart meter data (or standard dwelling calculation).
- 2. This Simulator’s Additions Method: Each planned load (heat pump, EVSE, induction range, HPWH, dryer) is added at 100% of its typical draw with no demand-factor reduction applied. §120.83(B) actually permits an 8 kVA-at-100%-then-40%-of-the-remainder tiering for general load additions on qualifying existing dwellings, which this simulator does not apply — so its "fits" verdict is conservative and may show less headroom than a full §120.83(B) calculation would.
- 3. Smart EMS Alternatives (Article 130): If the calculated total exceeds 100% of the main service breaker rating, an Energy Management System (EMS) or Smart Splitter can be installed to dynamically pause the EV charger when the heat pump or dryer runs, completely avoiding a panel upgrade!