⚡ NEC 2023 · Article 220

NEC Load Calculation Tool

Calculate residential and commercial electrical loads per NEC 2023 Article 220. Real engine output, traceable to every rule — free during Beta with your free account.

✓ NEC 2023 compliant ✓ Articles 220.82 & 220.87 ✓ Real calculations, not estimates

Load Calculation Inputs

NEC 2023 Art. 220.82 (Optional Method — Residential)

Building Type

Floor Area (sq ft)

Small Appliance Circuits

Laundry Circuits

HVAC — Largest Motor or A/C (amps)

Electric Range (watts, 0 if gas)

Electric Water Heater (watts, 0 if gas)

Electric Dryer (watts, 0 if gas)

Service Voltage

How NEC load calculation works

NEC Article 220 defines two methods for calculating residential electrical service size: the Standard Method (220.82) and the Optional Method. EEP uses the Optional Method for single-family dwellings, which typically yields a smaller (and more accurate) service size for modern homes with electric heat.

Step 1 — General loads (NEC 220.82(B))

Calculated at 3 VA/ft² for the first 3,000 ft², then 2 VA/ft² for the remainder. Small appliance and laundry circuits are added at 1,500 VA each per NEC 210.11(C).

Step 2 — Heating and A/C (NEC 220.82(C))

The larger of heating or cooling load is used at 100%. This prevents double-counting since both systems rarely run simultaneously.

Step 3 — Fixed appliances (NEC 220.82(B))

Range, water heater, dryer, and other fixed appliances are added at their nameplate rating. Ranges ≤ 12 kW use 8 kW per Table 220.55.

Step 4 — Service sizing (NEC 230.79)

Total VA is divided by service voltage to get minimum amperage. The next standard service size (100A, 150A, 200A, 400A) is selected per NEC 230.79.

Example: 2,400 ft² Single-Family Home (NEC 220.82)

Inputs

Standard 3-bed, 2-bath residence

2,400 ft² conditioned area · 2 small appliance circuits · 1 laundry circuit · 28A A/C · 12 kW range · 4.5 kW water heater · 5 kW dryer · 120/240V service

Result

Minimum 200A service recommended

General load: 10,200 VA · Small appliance/laundry: 4,500 VA · Range (Table 220.55): 8,000 VA · Water heater: 4,500 VA · Dryer: 5,000 VA · A/C: 6,720 VA · Total: 38,920 VA = 162A @ 240V → 200A service

Frequently asked questions

What is the NEC Optional Method for residential load calculation? ▾

NEC 220.82 (Optional Calculation for Dwelling Units) allows a simplified calculation that typically produces a smaller result than the Standard Method of 220.83. It calculates a general load at a reduced VA/ft² rate and adds the larger of heating or cooling. It's the most commonly used method for sizing residential services in the US.

What's the minimum service size required by NEC? ▾

NEC 230.79(C) requires a minimum 100-ampere, 3-wire service for single-family dwellings. Most modern homes with electric appliances and A/C require 200A. The calculated load determines the minimum; the AHJ may require a larger service.

Do I need to account for future loads in NEC load calculations? ▾

NEC doesn't require adding future loads, but good engineering practice does. The NEC calculation is a minimum. For EV chargers, solar inverters, or future additions, many engineers add 20–25% to the calculated load when sizing the service and panel. EEP's Pro plan includes a future-load planning field.

How do I calculate load for a commercial building? ▾

Commercial load calculation uses NEC Article 220 Part III, starting with 3.5 VA/ft² for general lighting (office) per Table 220.12, adding receptacle loads, HVAC, and specific-purpose equipment. Demand factors from Table 220.42 apply when there are multiple receptacles. Select "Commercial / Multi-family" in the tool above.