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Electrical load calculation for an EV charger: a worked example

Updated 2026-11-03 · Step-by-step home electrical load calculation for adding a Level 2 EV charger, worked in the 2020/2023 and 2026 NEC existing-dwelling methods and the 12-month utility data method.

An electrical load calculation answers one question: with the new charger added, what does the code method say your house draws, in amps, compared with your service rating? This page works one realistic example three ways so you can see how the numbers move. All arithmetic below is reproduced by our calculator.

The example house

1,800 sq ft, 100 A service, gas range, gas furnace and gas water heater. Electric loads on their own circuits: dryer 5,000 VA, dishwasher 1,200 VA, central A/C 4,000 VA. The owner wants a 48 A Level 2 charger (60 A circuit, 11,520 VA). Assumption: illustrative values, not a real house; use your own nameplates.

Method 1: 220.83, 2020 or 2023 NEC

StepVA
Lighting, 1,800 sq ft × 3 VA5,400
Two small-appliance circuits + one laundry circuit × 1,500 VA4,500
Dryer + dishwasher + A/C nameplates10,200
New EV charger, 48 A × 240 V11,520
Total31,620
First 8,000 VA at 100%8,000
Remaining 23,620 VA at 40%9,448
Calculated load (17,448 VA ÷ 240 V)≈ 72.7 A
Calculated load about 73 A versus service rating 100 A: within the rating with about 27% headroom under this method.

Method 2: 120.83, 2026 NEC

Lighting drops to 2 VA per sq ft (3,600 VA), so existing load is 18,300 VA: 8,000 VA at 100% plus 10,300 VA at 40% = 12,120 VA. The new charger counts at 80%: 9,216 VA. Total 21,336 VA, or ≈ 88.9 A. Same house, about 16 A higher, because the new charger no longer rides in the 40% tier. Assumption: 2026 factors from secondary sources (NEC Mastery: NEC 220.83 explained, with the 2026 changes; Electrical License Renewal: 120.83 Existing Dwelling Units (2026 summary)), not yet checked against NFPA 70-2026.

Method 3: 220.87, 12 months of utility data

If the utility reports a highest 15-minute peak of 6 kW over the last year (an illustrative figure): 6,000 × 125% = 7,500 VA, plus the charger at full nameplate 11,520 VA = 19,020 VA, or ≈ 79.3 A. Our calculator adds the new load at 100% here as a conservative choice (Intrysys: residential load calculator (220.82 / 220.87)).

Open this example with all three methods →

What the numbers do not tell you

  • A result within rating is a calculation result, not a finding that the installation is acceptable. The electrician still checks service conductors (NEC 310.12), the panel busbar rating and free breaker spaces.
  • Some AHJs count EV chargers at 100% in the existing-dwelling method (TradeTools: existing service load calculator (AHJ variants, 220.57)). Our calculator has a toggle for that.
  • If the result is close or over, see EV load management (NEC 625.42) or a lower charger setting.

Related: Can a 100 amp panel handle an EV charger? · NEC 220.83 explained · Which NEC edition applies

Common questions

How many amps does an EV charger add to a load calculation?

Its nameplate or set rating at 240 V: a 48 A charger is 11,520 VA (48 A × 240 V). In the 2023 edition, 220.57 sets a floor of 7,200 VA or the nameplate, whichever is larger. How much of that counts depends on the method and edition.

Why can the 2026 NEC give a higher answer for an EV charger?

In our reading of secondary summaries of 120.83, a new EV charger counts at 80% instead of falling into the 40% remainder, which can outweigh the lower 2 VA per sq ft lighting load. Treat this as unverified until checked against printed NFPA 70-2026.

Can I use my utility bills instead of a calculation?

Yes, 220.87 allows the highest 12 months of measured peak demand × 125% plus the new load, if your utility can provide demand data. Your AHJ decides whether it accepts the data.

Estimate only; a licensed electrician and your local authority having jurisdiction decide; not an engineering stamp.

Taking it to your electrician or the permit desk? The worksheet is free to print. A formatted permit-style PDF with a saved house is $9 one-time; electricians get branded PDFs, unlimited jobs and client links with Pro at $19/month.

Sources

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