A full, step-by-step NEC Article 220 load calculation for a representative single-family home, showing general lighting load, appliance demand factors, HVAC, and the final required service size.
The Scenario
This example walks through a standard-method NEC Article 220 load calculation for a representative single-family home: 2,400 sq ft, 240V single-phase service, with a electric range (12 kW), electric dryer (5.5 kW), dishwasher (1.2 kW), garbage disposal (0.5 kW), microwave (1.5 kW), and a 4-ton (48,000 BTU/hr) heat pump with 10 kW electric backup heat. This is an illustrative walkthrough, not a substitute for a project-specific calculation performed against the actual current code edition and the specific house's actual equipment.
Step 1 — General Lighting and Receptacle Load
Using a general lighting unit load for dwelling occupancies (commonly cited around 3 VA/sq ft, though this should always be verified against the current code edition): 2,400 sq ft × 3 VA/sq ft = 7,200 VA. Two 20A small-appliance branch circuits (kitchen) and one laundry circuit are also required by code regardless of calculated load, each counted at 1,500 VA per Article 220's specified value: 3 × 1,500 = 4,500 VA. Total general lighting + required circuits = 7,200 + 4,500 = 11,700 VA.
Step 2 — Applying the Demand Factor to General Lighting
Article 220's demand factor for dwelling general lighting/receptacle load applies the first several thousand VA at 100%, with a reduced percentage applied beyond that threshold. Using an illustrative structure: first 3,000 VA at 100% = 3,000 VA; remaining 8,700 VA at 35% = 3,045 VA. Demand load for this category = 3,000 + 3,045 = 6,045 VA. (Always verify the current code edition's exact threshold and percentage — these have been adjusted between editions.)
Step 3 — Fixed Appliance Loads
Dishwasher (1,200 VA) + garbage disposal (500 VA) + microwave (1,500 VA) = 3,200 VA connected. With four or more fixed appliances (not counting range, dryer, and HVAC, which are calculated separately), Article 220 permits a demand factor — using an illustrative 75%: 3,200 × 0.75 = 2,400 VA. (With fewer than four qualifying fixed appliances, this demand factor doesn't apply and each is counted at nameplate value.)
Step 4 — Electric Range
Electric ranges have their own dedicated demand factor table in Article 220, reflecting that a range rarely operates at its full nameplate rating continuously. For a single 12 kW range, the applicable demand load (per the code's range demand table) is commonly around 8 kW = 8,000 VA — always confirm the exact value against the current table, since it's based on both the nameplate rating and the number of ranges being served.
Step 5 — Electric Dryer
Dryers are calculated at nameplate rating or a minimum value specified by code, whichever is larger, with a demand factor applied only when multiple dryers serve multiple dwelling units (not applicable to a single-family home): 5,500 VA (nameplate) — no demand reduction for a single dwelling unit's single dryer.
Step 6 — HVAC Load (Largest of Heating or Cooling)
Article 220 requires including the larger of the heating or cooling load, not both simultaneously (since they don't operate at the same time). Heat pump cooling: 4-ton system, roughly 4 × 1,000 VA/ton (illustrative) ≈ 4,000 VA. Electric backup heat: 10,000 VA — this exceeds the cooling load and includes consideration of whether the heat pump compressor runs concurrently with backup heat per the specific equipment's control sequence. Using the larger value: 10,000 VA (backup heat, since it can operate concurrently with the compressor on many systems — always verify against manufacturer data and code requirements for the specific equipment).
Step 7 — Total and Service Size
Summing all demand loads: general lighting/receptacle (6,045) + fixed appliances (2,400) + range (8,000) + dryer (5,500) + HVAC (10,000) = 31,945 VA. At 240V single-phase: 31,945 ÷ 240 ≈ 133 A. This would round up to a standard 150A service — a 100A service would be undersized for this load; a 200A service, while larger than strictly required, is common practice to accommodate future load growth (an EV charger, for example) without a future service upgrade.
What This Example Deliberately Simplifies
This walkthrough uses illustrative demand factor percentages and thresholds to keep the example legible — always pull the exact current values from the specific NEC edition governing your project, since these tables have been adjusted between editions (see this site's Standards & Codes for NEC edition tracking). This example also doesn't include an EV charger or additional loads that a real project might have — see the companion multifamily/EV-load example article for that scenario.