Calculation. This scoped 2026 NEC 120.82 planning estimate uses 2 VA per square foot, plus 1,500 VA for each entered small-appliance and laundry circuit. It applies 100% to the first 8,000 VA of general and fixed-appliance load, then 40% to the remainder. One supported HVAC system and EV equipment nameplate loads are added at 100%. The trace above shows each amount.
Area and circuits. Include an attached garage in dwelling area. Exclude detached garages, open porches, and unfinished areas not adaptable to future occupancy. Room lighting and general circuit VA are already represented by the area allowance, so they are not added again to the service total. EV service load uses 100% nameplate. For main-rating planning, continuous appliances leave the demand-adjusted general subtotal and are reserved at 125%; continuous HVAC and EV loads are reserved at 125%. Continuous general-circuit loads are reserved at 125% while the area allowance remains, making this suggestion conservative. This sizing step is separate from the service-demand calculation.
Automatic sizing. Auto mode keeps the main selection, panel spaces, slot map, and schedule synchronized with valid inputs. Selecting a main or panel size manually switches to Manual. Panel space depends on the entered circuit poles and planned spares; an area change does not invent branch circuits. Standard sizes change only when a threshold is crossed.
Limits. Panel slots and leg bars illustrate the entered circuits. The suggested main rating and spare spaces are planning choices, not code minimums. Breaker, bus, conductor, protection, equipment compatibility, utility requirements, and locally adopted code still require qualified review.
References: 2026 NEC changes to dwelling calculations ↗; attached-garage clarification ↗; continuous-load sizing clarification ↗; NFPA 70 ↗.
