Load calculator
The EV charger load calculation, in plain English
Whether your panel can take a charger is not a guess and not a sales conversation. It is arithmetic the code book already prescribes. This page shows you exactly what gets calculated; the assessment runs it on your real numbers.
What is an EV charger load calculation?
The NEC Article 220 math that decides whether your panel can carry a charger.
Sum the home's general lighting load, small-appliance and laundry circuits, fixed appliance nameplates, and the larger of heating or A/C; apply the demand factor the code allows; add the EV charger as a continuous load; compare the total to the service rating. For an existing home adding a charger, NEC 220.83(A) is normally the governing section. Run it on your home's numbers for $49.99.
NEC References:
- NEC 220.83(A)
- NEC 220.82
- NEC 230.79
Last updated: August 2026
Which NEC section governs your home
Which section binds is a situational determination, and the honest answer starts there — not with a one-size formula:
| Your situation | Governing section |
|---|---|
| Existing home, adding a charger — the usual case | NEC 220.83(A), Existing Dwelling Unit |
| Existing home, adding a charger and new heating or A/C | NEC 220.83(B) |
| New construction, or a full service change | NEC 220.82, Optional Method |
The full plain-English walkthrough of the methods lives on the methodology page, and what the tool deliberately does not do is on limitations.
A worked example: 100A panel, gas heat
A 1,500 sqft home with a gas furnace, 2.5-ton central AC (30A breaker), electric range (40A), electric dryer (30A), gas water heater, and a dishwasher, under NEC 220.83(A):
| Calculation step | VA |
|---|---|
| General lighting (1,500 sqft × 3 VA) | 4,500 |
| Small appliance + laundry (3 × 1,500) | 4,500 |
| Electric range | 8,000 |
| Electric dryer | 5,000 |
| Dishwasher | 1,500 |
| Total before demand | 23,500 |
| First 8,000 VA at 100% (220.83(A)) | 8,000 |
| Remaining 15,500 VA at 40% | 6,200 |
| AC load (30A × 240V) | 7,200 |
| Demanded load without EV | 21,400 VA (~89A) |
The ~89A demanded load already sits past the 80% advisory comfort line of a 100A panel (80A) — still under the panel's full 100A rating, so it passes the NEC 230.79 pass/fail test, but with little headroom left. Add a 24A charger (5,760 VA) and the total reaches 27,160 VA, roughly 113A: past the panel's full rating, a genuine fail rather than a tight pass. For this home the paths to evaluate are a lower configured charging rate, a listed load-management system, or a service change — and which one holds up is exactly what the calculation on 100-amp panels works through in detail.
Change one input — gas range instead of electric, a smaller AC, a 16A charging rate — and the verdict can flip. That input-sensitivity is why a panel rating alone, or a contractor's glance, cannot answer the question. The code section written for an existing home adding a load, NEC 220.83(A), exists precisely to answer it with arithmetic.
How ChargeRight reads 220.83(A) for the AC and the charger. In the worked example above — and in the assessment engine — the existing air conditioning and the new EV charger are each counted at 100 percent, outside 220.83(A)'s first-8-kVA/40-percent demand-factor pool, rather than folded into the pool at a reduced percentage. That is ChargeRight's own conservative interpretation of how those loads should be treated alongside 220.83(A)'s table — not a claim about what the code text itself explicitly states, and not the only defensible reading. A literal reading that folds them into the pool produces a lower demanded load; ChargeRight errs toward the reading that asks for more headroom, because the cost of the loose direction is a homeowner told to skip an upgrade they actually needed. The charger line above is carried at its nameplate (24A × 240V = 5,760 VA) in this method's service total; the 125-percent continuous factor governs the charger's breaker and circuit sizing (NEC 625.41), which the assessment sizes separately.
What the assessment runs for you
- The applicable NEC Article 220 calculation on your real inputs — square footage, appliance nameplates, heating and cooling, the charger your car needs — with panel photos if you add them.
- All methods computed and shown as cross-checks; the report names the section that actually governed.
- The exact circuit-size answer (the 30, 40, 48, or 50 amp question), sized for continuous load the way the code requires.
- Every line of the math on a one-page report you can hand a licensed electrician.
It costs $49.99 flat. It is not a permit, a final electrical design, or an installation service — the electrician who pulls your permit and the local inspector are always the final word.
Stop guessing at your panel.
The NEC Article 220 answer, on your numbers, in minutes.
Start the assessment — $49.99Frequently asked questions
What is an EV charger load calculation?
It is the NEC Article 220 arithmetic that determines whether an electrical service can carry an EV charger: sum the general lighting load, small-appliance and laundry circuits, fixed appliance nameplates, and the larger of heating or A/C, apply the demand factor the code allows, add the charger as a continuous load, and compare the total to the service rating.
Which NEC section applies to my home?
For an existing home adding a charger with no new heating or A/C — the usual case — NEC 220.83(A) applies. Adding new space-conditioning equipment alongside the charger moves it to 220.83(B). NEC 220.82 is the section for new construction or a full service change. The report names the section that actually governed rather than assuming one.
Is the pass/fail line 80% of my panel rating?
No. The pass/fail test is NEC 230.79: the calculated load against the service's full rating. 80% of rating is an advisory comfort line — useful for judging headroom, but not the code cutoff.
Can I run the load calculation myself?
The method is public — NEC Article 220 is the same code book every electrician uses, and this page shows a worked example. Getting a dependable answer for a specific home means getting every input right: square footage, each appliance nameplate, the heating/cooling loads, and the charger amperage. ChargeRight runs all applicable methods on your real numbers for $49.99 and shows the arithmetic.
What does the ChargeRight assessment include?
The NEC Article 220 load calculation run on your inputs (with panel photos if you add them), the exact circuit-size answer for the charger your car needs, the section that governed and every line of the math, and a one-page report you can hand a licensed electrician. It is $49.99 flat — it is not a permit, a final electrical design, or an installation service.
Do I need a 200-amp panel for an EV charger?
Not necessarily. Whether a 100A or 150A service can take a charger depends on the calculated load of everything already on it, not the rating stamped on the door. Many homes with gas heat pass with room to spare at a 24A or 32A charging rate; all-electric homes are often genuinely tight. The calculation decides.