Sizing a 200A Residential Service
Complete NEC 220 residential service calculation for a 2,500 sq ft home — lighting, appliances, HVAC, and service entrance sizing.
Scenario Overview
Walk through a complete NEC 220.82 (optional method) residential service calculation for a typical 2,500 sq ft single-family home with central A/C, electric range, dryer, and water heater.
Given Information
- •2,500 sq ft single-family dwelling
- •200A, 120/240V single-phase service
- •Central A/C: 5 tons (30A, 240V)
- •Electric range: 14 kW
- •Electric dryer: 5.5 kW
- •Water heater: 4,500W
- •Dishwasher: 1,500W
- •Garbage disposal: 1 HP (960W)
Calculation Steps
General Lighting Load
NEC 220.12: General lighting load = 3 VA per square foot.
2,500 ft² × 3 VA/ft² = 7,500 VA
Result: 7,500 VA general lighting
Small Appliance & Laundry Circuits
NEC 220.52(A): Minimum 2 small appliance circuits × 1,500 VA = 3,000 VA.
NEC 220.52(B): 1 laundry circuit × 1,500 VA = 1,500 VA.
Result: 4,500 VA (small appliance + laundry)
Apply Demand Factor to Lighting/Receptacles
Total: 7,500 + 4,500 = 12,000 VA.
NEC Table 220.42: First 3,000 VA at 100% = 3,000 VA. Remaining 9,000 VA at 35% = 3,150 VA.
Result: 6,150 VA after demand
Range Demand (NEC Table 220.55)
14 kW range: Column C for 1 range = 8 kW base + 5% per kW over 12 kW.
14 − 12 = 2 kW over. 8,000 × 1.10 = 8,800 VA.
Result: 8,800 VA range demand
Dryer Demand (NEC 220.54)
Nameplate 5,500W > 5,000W minimum, so use 5,500 VA.
Result: 5,500 VA dryer
Fixed Appliances
Water heater: 4,500 VA
Dishwasher: 1,500 VA
Disposal: 960 VA
Total fixed: 6,960 VA
NEC 220.53: 4+ fixed appliances at 75% = 6,960 × 0.75 = 5,220 VA
Result: 5,220 VA fixed appliances (after 75% demand)
HVAC Load
A/C: 30A × 240V = 7,200 VA
No heating load — NEC 220.60 says use larger of heating or cooling.
A/C dominates at 7,200 VA.
Result: 7,200 VA A/C
Total Demand and Service Sizing
Total: 6,150 + 8,800 + 5,500 + 5,220 + 7,200 = 32,870 VA.
Service amps: 32,870 / 240 = 137A.
200A service is adequate with significant margin.
Result: 137A demand — 200A service confirmed adequate
Final Answer
Total calculated demand: 32,870 VA (137A). A 200A, 120/240V service with 2/0 AWG copper or 4/0 AWG aluminum service entrance conductors is adequate. GEC sized per NEC 250.66.
Key Takeaways
- •The NEC optional method (220.82) often yields a lower demand than the standard method — always check both
- •HVAC uses the larger of heating or cooling load, never both (NEC 220.60)
- •Fixed appliances with 4+ units get a 25% demand reduction (NEC 220.53)
- •Range demand from Table 220.55 significantly reduces the connected load
Calculators Used
NEC References
- NEC 220.42 — Lighting Demand Factors
- NEC 220.52 — Small Appliance/Laundry
- NEC 220.53 — Fixed Appliance Demand
- NEC 220.54 — Dryer Demand
- NEC 220.55 — Range Demand
- NEC 220.60 — Noncoincident Loads