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Electrical Service Sizing
Dwelling unit and multifamily building service calculations per NEC Article 220. ← Back to Tools
Project Information (optional · click to expand)
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Firm
Project
Fields populate the Revit text output header and the (forthcoming) Word load letter. Firm info can be remembered per-device; project info is per-project (not saved). Tool is generic — enter your own firm details.
Step 1 · Method
Method
Optional calculation for a single dwelling unit. 120/240V, single-phase, 100A minimum service.
Per PSE&G IRES Table 2-1. 3Φ supply is not normally available for residential service per IRES Tables 6-1/6-2 footnote; selecting 3Φ for §220.82/83/84 will surface a warning. Voltage class affects amperage calc, CT cabinet threshold, max service size, and transformer sizing.
General Loads
Small-Appliance Circuits are the dedicated 20 A kitchen-counter receptacle circuits required by NEC §210.11(C)(1). Each counts as 1,500 VA per §220.52(A). Most dwellings have 2. Laundry Circuits are the dedicated 20 A laundry-receptacle circuits required by §210.11(C)(2). Each counts as 1,500 VA per §220.52(B). Typically 1 per dwelling.
HVAC Equipment
List each piece of HVAC equipment separately. Tool aggregates by type and applies §220.82(C) "largest of six selections" automatically. Multiple AC condensers sum into the cooling pool. Mixed systems (heat pump + resistive backup, central + mini-split, etc.) all in one place.
Appliances & Other Loads
ApplianceVA EachQty
EV Charging Load
Enter raw nameplate amps from the EVSE spec sheet. Tool applies §625.41 (125% continuous) and computes service-load VA. Common: Level 2 @ 32 A or 40 A × 240 V. Multiple chargers default to no diversity per §625.42 — for ALMS-equipped installs, enter the ALMS-permitted maximum amps as a single charger.
Add one card per unit type (e.g. Studio, 1BR, 2BR). Set a quantity for each. Expand a card to configure its loads — SF, HVAC, appliances, EV. The §220.84 method sums each unit's connected load at 100% nameplate per (C), then applies a single Table 220.84 demand factor based on total unit count. House loads are added separately as Part III per §220.84(B).
House Load · Common Area · §220.84(B) Part III
Common-area loads (corridors, basement, elevators, fire pump, common HVAC and pumps, common-area EV chargers) calculated under Article 220 Part III, then added to the dwelling demand per §220.84(B). Mirrors the unit-type card structure but uses non-dwelling demand factors (Tables 220.42, 220.44, 220.53, 220.54, 220.55, §430.24).
Results
Output format:
Per 2020 NEC per N.J.A.C. 5:23-3.16 — Article 220 Parts II–IV (§§220.12, 220.42, 220.52, 220.53, 220.54, 220.55, 220.60, 220.82, 220.83, 220.84), Article 230 (§§230.42, 230.79), Article 430 (§430.24), Article 625 (§§625.41, 625.42), and N.J.A.C. 5:23-3.16. Verify all calculations against current adopted code edition. Service conductor sizing per Article 310 not included — verify with manufacturer ampacity tables. Green Stories LLC is a building design and consulting firm.