Service Load Calculations
Worked Examples (Article 220 Parts III–IV, 310.12, 230.42, Table 250.66, 450.3)
NFPA 70 National Electrical Code, 2023 edition · Reviewed 2026-09-21
Services, Service Equipment and Separately Derived Systems is the biggest calculation block of the Georgia PSI exams. Every problem is one of: the dwelling standard method, the dwelling optional method, the existing dwelling table, the multifamily optional table, a commercial building (lighting + receptacles + kitchen equipment + motors), sizing the service conductors / neutral / GEC, or a transformer primary/secondary. Georgia tests the 2023 text: Article 220, dwelling general lighting 3 VA/ft², optional-method first tier 10 kVA, EVSE at 7200 W or nameplate, whichever is larger, Table 220.83(A)/(B) for existing dwellings. Written from the 2023 text (viewer p.95–104, 112–118, 186, 376–380).
1. Dwelling — standard method (Article 220 Part III)
| Step | Rule | Amount |
|---|---|---|
| General lighting and receptacles | 220.41 | 3 VA/ft² of floor area (outside dimensions; exclude open porches and unfinished spaces not adaptable for future habitable use) |
| Small appliance | 220.52(A) | 1500 VA × each 20 A small-appliance circuit (minimum two) |
| Laundry | 220.52(B) | 1500 VA |
| Demand on the three above | Table 220.45 | first 3000 VA at 100 %; 3001–120,000 VA at 35 %; remainder 25 % |
| Fastened-in-place appliances | 220.53 | nameplate; 75 % where four or more rated ¼ hp or 500 W or more (not cooking equipment, dryers, space heating, A/C, EVSE) |
| Dryers | 220.54 / Table 220.54 | 5000 W or nameplate, whichever larger; 1–4 at 100 %, 5 at 85 %, 6 at 75 %, 7 at 65 %, 8 at 60 %, 9 at 55 %, 10 at 50 %, 11 at 47 % … |
| Ranges / cooking > 1¾ kW | Table 220.55 | Column C: one range ≤ 12 kW = 8 kW; Note 1: + 5 % per kW over 12 kW |
| Heating vs A/C | 220.60 / 220.51 / 220.50 | the larger of the two (noncoincident); heat at 100 %; A/C per 440 Part IV; a motor or A/C load that is not the larger is compared at 125 % |
| Motors | 220.50 | 125 % of the largest motor (430.24) |
| EVSE | 220.57 | 7200 W or nameplate, whichever is larger |
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