NEC 220.82 Optional Method: Full Worked Example for a 2,000 SF House with EV Charger

The customer wants a panel upgrade to handle a new heat pump and an EV charger. The standard load calculation under NEC Article 220 returns 167A — technically under 200A, but the contractor is worried the AHJ will flag it as too close to the service rating. Running the same house through NEC 220.82’s optional method returns 121A, with documented headroom to spare. Both are code-compliant. Here’s the full arithmetic for a 2,000 sq ft house so you can see exactly where the 46A difference comes from.

When the Optional Method Applies

NEC 2023 § 220.82 applies to existing or new single-family dwellings served by a single 120/240V (or 120/208V), 3-wire service or feeder with a calculated load of 100A or more. It cannot be used for multifamily units using a single service or for anything other than the described service configuration.

Source: NFPA 70 (NEC), 2023 edition, § 220.82. Note: In the 2026 NEC, this section moves to § 120.82 as part of the major article renumbering. The calculation method is unchanged in 2026 except for one significant input: the general lighting load drops from 3 VA/sq ft to 2 VA/sq ft. If your AHJ has adopted the 2026 NEC, substitute 2 VA/sq ft in Step 1 below.

The House: Loads and Nameplate Data

2,000 sq ft single-family dwelling, 240V/120V single-phase service:

Load	Nameplate / Rule	VA
General lighting (3 VA/sq ft × 2,000 SF)	NEC 220.12	6,000
Small appliance circuits (2 required)	1,500 VA each	3,000
Laundry circuit	1,500 VA	1,500
Electric water heater	4,500 W nameplate	4,500
Electric range	12,000 W nameplate	12,000
Dishwasher	1,200 W nameplate	1,200
Clothes dryer	5,500 W nameplate	5,500
Level 2 EV charger (40A circuit)	40A × 240V	9,600
General load subtotal		43,300
Heat pump (4-ton, 240V, 24A nameplate)	24A × 240V	5,760

The heat pump is handled separately from the general loads in Step 3. Everything else goes into the general load pool in Step 1.

NEC 220.82 Optional Method — Full Calculation

Step 1 — Sum the General Loads (220.82(B))

Add all loads except the HVAC:

6,000 + 3,000 + 1,500 + 4,500 + 12,000 + 1,200 + 5,500 + 9,600 = 43,300 VA

Step 2 — Apply the Demand Factor (220.82(B))

NEC 220.82(B) Demand Factor

First 10,000 VA: 100%

All VA over 10,000: 40%

$$Demand_{general} = 10{,}000 + [(43{,}300 - 10{,}000) \times 0.40]$$ $$= 10{,}000 + [33{,}300 \times 0.40] = 10{,}000 + 13{,}320 = \mathbf{23{,}320 \text{ VA}}$$

Step 3 — Add the HVAC Load (220.82(C))

Under 220.82(C), you include the largest of the heating and cooling loads, but not both. For this house, there is only a heat pump (no backup resistance heat), so the HVAC contribution is:

5,760 VA at 100% (the optional method includes heat pump loads at 100% of nameplate under 220.82(C)(5))

Step 4 — Total Demand Load

$$Total_{demand} = 23{,}320 + 5{,}760 = \mathbf{29{,}080 \text{ VA}}$$

Step 5 — Service Size

$$I_{service} = \frac{29{,}080}{240} = \mathbf{121.2 \text{ A}}$$

Round up to the next standard service size: 200A service. The optional method calculates 121A of demand against a 200A service, leaving 79A of documented capacity for future loads.

Standard Method Comparison: Same House, Same Loads

The standard method (NEC 220.12 + 220.14 + 220.55 etc.) applies different demand factors to each load category. For the same 2,000 SF house:

Load	Standard Method Calc	Demand VA
Lighting + SA + Laundry (10,500 VA total)	First 3,000 VA at 100% + 7,500 VA at 35%	5,625
Water heater	4,500 VA at 100%	4,500
Range (Table 220.55, Col C, 1 unit ≤ 12 kW)	8,000 VA demand	8,000
Dishwasher	1,200 VA at 100%	1,200
Dryer (Table 220.54, 1 unit)	5,500 VA at 100%	5,500
EV charger (continuous load)	9,600 VA at 100%	9,600
Heat pump	5,760 VA at 100%	5,760
Standard method total demand		40,185 VA

Service: 40,185 ÷ 240 = 167.4A → 200A service

Both methods arrive at a 200A service. The difference is the calculated demand — 121A under the optional method vs. 167A under the standard method. That 46A difference is documented headroom the AHJ sees when reviewing the permit application.

Tip

The optional method almost always produces a lower calculated demand than the standard method. The 40% demand factor on the bulk of general loads is more aggressive than the per-category demand factors in Article 220. For houses with large connected loads (ranges over 12 kW, multiple dryers, large EV chargers), the optional method’s single demand factor pool compresses those loads more than the standard method’s table-by-table approach.

The 2026 NEC Change: 2 VA/sq ft Lighting

If your AHJ has adopted the 2026 NEC (which renumbers this section as § 120.82), the general lighting unit load drops from 3 VA/sq ft to 2 VA/sq ft — a 33% reduction that directly affects the general load total:

	2023 NEC	2026 NEC
General lighting (2,000 SF)	6,000 VA	4,000 VA
All other general loads (unchanged)	37,300 VA	37,300 VA
General load total	43,300 VA	41,300 VA
First 10,000 VA at 100%	10,000	10,000
Remainder at 40%	13,320	12,520
General demand subtotal	23,320	22,520
HVAC (unchanged)	5,760	5,760
Total demand	29,080 VA (121A)	28,280 VA (118A)

Under 2026 NEC, the same house calculates to 118A rather than 121A — a 3A improvement, both well within a 200A service. The 2026 lighting load change matters more for large commercial buildings where the lighting load represents a significant portion of total demand.

What to Document for the Permit

AHJs vary on how much detail they want for residential load calculations, but a clean permit submittal for a 220.82 optional method calculation includes:

NEC edition and section number used (NEC 2023 § 220.82 or 2026 § 120.82)
Conditioned floor area and the unit load used (3 or 2 VA/sq ft)
Itemized load inventory matching nameplate data
The two-tier demand factor calculation shown explicitly (first 10,000 VA at 100%, remainder at 40%)
HVAC nameplate reference and the 220.82(C) subsection applied
Final total demand in VA and resulting ampere load

Some inspectors are accustomed to seeing the standard method and are unfamiliar with the optional method. Citing the NEC section number and showing the demand factor calculation explicitly avoids back-and-forth at plan review.

For individual circuit load calculations that feed the whole-house number, see how to calculate electrical load for new circuits. To verify the panel can handle the distribution of loads across both legs, the 200A panel load balance post covers leg assignment and remaining capacity. For the EV charger circuit sizing that drove the 9,600 VA input in this calculation, see EV charger circuit sizing under NEC 625.

The electrical load calculator handles both the optional method and the standard method for residential services — enter nameplate values for each load and it returns the 220.82 optional demand, the standard method demand, and the required service size under each method.