NEC 220.87 for EV Chargers: Using Recorded Demand in a Service-Load Check (2026)

Most homeowners who get a panel-upgrade quote alongside an EV charger install never hear NEC 220.87 mentioned. The quote may use a calculated Article 220 method (or, in some cases, no calc at all and a rule-of-thumb estimate), lands close to the service rating, and the homeowner gets a $4,000 service upgrade attached to a $1,500 charger install. The 220.87 path is the existing-loads rule the NEC wrote for exactly this situation: when a dwelling has been lived in long enough to have real utility demand data, the calc gets to use the real data instead of the conservative estimate.

The Rule in Plain English: NEC 220.87 Verbatim

NEC 220.87 (2017 edition) reads: "The calculation of a feeder or service load for existing installations shall be permitted to use actual maximum demand to determine the existing load under all of the following conditions: (1) The maximum demand data is available for a 1-year period."

The exception, verbatim: "If the maximum demand data for a 1-year period is not available, the calculated load shall be permitted to be based on the maximum demand (the highest average kilowatts reached and maintained for a 15-minute interval) continuously recorded over a minimum 30-day period using a recording ammeter or power meter connected to the highest loaded phase of the feeder or service, based on the initial loading at the start of the recording. The recording shall reflect the maximum demand of the feeder or service by being taken when the building or space is occupied and shall include by measurement or calculation the larger of the heating or cooling equipment load, and other loads that may be periodic in nature due to seasonal or similar conditions."

The second condition, paraphrased from the NEC 2017 text continuing past the cutoff, requires that the existing maximum demand at 125 percent plus the new load not exceed the ampacity of the feeder or the rating of the service. That is the math line. Existing demand times 1.25, plus new EV load, compared to the service rating.

In one sentence, NEC 220.87 says: if there is real demand data for an occupied dwelling, use it, multiply it by 1.25, add the EV, and check it against the service. This is a different evidence path from the calculated Article 220 dwelling methods; it does not guarantee a higher or lower result.

The Math: A Worked Example

This illustrative comparison uses a 1,900 sqft 1995-built ranch on a 200A service, gas heat, central AC, electric range, electric dryer, electric water heater. Two adults, one teenager, a Ford Mustang Mach-E about to land in the driveway with an 11.5 kW / 48A continuous Ford Connected Charge Station. An electrician from a national installation-referral network used a 220.82 cross-check and landed at 186A (under the 200A service rating, so it passes NEC 230.79, though 26A over the 160A advisory comfort line), then quoted the charger plus a $4,200 service upgrade.

The homeowner's 12-month utility history told a different story. Peak demand over the prior twelve months was 14.8 kW, recorded in July during the air-conditioning peak with the dryer and electric range running.

• Existing peak demand: 14.8 kW = 14,800 VA. At 240V single phase, 14,800 ÷ 240 = 61.7A actual recorded peak.
• Existing demand at 125 percent (NEC 220.87 condition 2): 14,800 × 1.25 = 18,500 VA = 77.1A.
• New EV load (NEC 625.41 continuous, 125 percent): 48A × 240V = 11,520 VA; 11,520 × 1.25 = 14,400 VA = 60A.
• Total under NEC 220.87: 77.1A + 60A = 137.1A.
• Service rating: 200A.
• Headroom: 62.9A available.

With these illustrative inputs, the house that landed at 186A under the 220.82 cross-check lands at 137.1A under the 220.87 actual-demand method. The difference demonstrates why the methods should be compared when the data and AHJ permit it; it is not a prediction that one method will always be lower.

Run the same calc on your own panel for $49. The assessment binds NEC 220.83(A) for an existing home adding a load and shows the NEC 220.82 number alongside it as a cross-check. It does not compute 220.87 - bring the report to your electrician and ask for that check against your utility's demand history.

Why 220.87 Can Differ From a Calculated Method

Calculated Article 220 methods use connected-load inputs and prescribed demand factors. A 220.82 comparison, for example, includes connected appliance and HVAC loads, then applies the first-10-kVA-at-100-percent and remainder-at-40-percent demand factor. It uses the prescribed inputs rather than the household's recorded operating pattern.

The 220.87 actual-demand method does know. The utility meter has been recording 15-minute interval averages for a year, and the worst 15-minute interval is the peak. It can differ from the calculated estimate for several reasons:

• Diversity. No occupied house runs every appliance simultaneously. The dryer, the range, the AC compressor, and the water heater do not all hit their peak in the same 15-minute window. 220.82 partially accounts for diversity with the 40 percent remainder factor; 220.87 measures the diversity directly.
• Behavior. Households schedule heavy loads to avoid each other without thinking about it. The dishwasher runs after dinner, the dryer runs in the morning, the AC is at its peak in the afternoon. The utility meter sees the actual schedule; the calc assumes simultaneous worst-case.
• Sub-nameplate operation. A 4-ton AC compressor rated at 5,000 watts continuous rarely draws that nameplate in a steady state; modern variable-speed compressors spend most of the cycle at 40 to 60 percent of nameplate. The calc uses the nameplate; the meter sees the actual.

The direction and size of the difference cannot be inferred from the panel rating. Use the qualifying demand record and the applicable calculated method, show both inputs, and let the locally accepted method determine the permit decision.

The 30-Day Recording Exception: When There Is No 12-Month History

New construction, recent move-ins, and any dwelling that does not have a full year of utility data is not shut out of 220.87. The exception lets a licensed electrician install a recording ammeter or power meter on the service for a minimum 30-day period and use the highest 15-minute average as the existing peak demand. Three conditions apply.

• Occupied. The recording has to be taken when the building is occupied, which keeps an empty-house reading from understating the demand.
• Heating or cooling included. The larger of the heating or cooling equipment load has to be included by measurement or calculation. A 30-day recording in May does not capture the July AC peak; the electrician calculates that load and adds it to the recorded number.
• Seasonal loads included. Pool pumps, electric heat strips, and other loads that are periodic in nature have to be included by measurement or calculation, same rule as the heating/cooling adder.

A 30-day recording costs $150 to $400 in most markets, including the meter rental, the install, the disconnect, and the data summary. For a borderline house that would otherwise face a $4,000 service upgrade, the recording is the cheapest possible tiebreaker.

When 220.87 Is Unavailable or Needs Extra Review

Use the method that matches the project and the locally accepted documentation.

• New construction or recent move-in with no recording option. 220.87 requires real data, either 12 months of utility history or a 30-day recording. A house that has been lived in for three months with no recording available cannot meet either condition. Use the applicable calculated path: normally 220.83(A) or 220.83(B) for an existing dwelling adding load, and 220.82 for new construction or a planned full service change. The NEC 220.82 walkthrough walks the calc line by line.
• Major load broken or disconnected during the recording window. If the heat pump compressor failed in March and the air handler ran on emergency heat strips for a month, the utility data understates the real load. Same problem if the electric water heater was off for two months during a remodel. In that case the record may not represent the required load conditions; document the gap and use the method the AHJ accepts.
• AHJ requires a different calculation or more documentation. Adoption and submittal requirements vary. Confirm the accepted path before treating 220.87 as the permit basis.

What the Honest Quote Looks Like

A 2026 EV charger quote that respects NEC 220.87 will include four details that the cheap bids tend to skip.

• The applicable calculated and recorded-demand paths identified. For an existing dwelling, the calculated path is normally 220.83(A) or 220.83(B); 220.82 belongs to new/full-service work or an explicitly labeled comparison. If 220.87 is used, show its source data and confirm AHJ acceptance.
• The utility demand summary attached. The 12-month peak kW or peak kVA reading from the utility, with the month it occurred. A 220.87 calc with no attached demand summary is not a 220.87 calc; it is a number on a sheet.
• The 125 percent math shown. Existing demand at 125 percent, plus new EV load, equals total. The condition (2) line of 220.87 is the formula and the bid should show it.
• The fallback path if the calc fails. When 220.87 lands above the service rating, the honest quote names the next step, NEC 625.42 automatic load management on the EV side, a sub-panel with arbitrated loads, or the actual service upgrade with the math behind it. The smart panel and load management post walks the EVEMS scope; the sub-panel vs service upgrade post walks the sub-panel scope.

The Expired 30C Credit and 220.87 Households

The federal Section 30C EV charger tax credit expired June 30, 2026. While it was active, it covered 30 percent of qualified expenditure up to $1,000 for the EV charger and the electrical work directly required to install it, and a service-upgrade install always hit the same $1,000 ceiling as a clean charger install, which meant the extra $4,000 panel-upgrade portion was paid by the homeowner with no offset. With the credit now gone, the entire install (charger plus any panel work) is out of pocket, so an unnecessary panel upgrade is a straight loss rather than a partially offset one.

For a borderline calculated result, 220.87 can provide another permitted evidence path when qualifying demand data exists and the AHJ accepts it. Before signing an upgrade bid, ask the electrician whether that path is available and require the calculation to be shown. The 30C install timeline post walks the history of the now-expired credit.

Where 220.87 Sits in the ChargeRight Workflow

For an existing home adding a charger without new HVAC, the $49 assessment binds NEC 220.83(A), the section written for that project situation. The questionnaire collects square footage, appliance inventory, HVAC system, and the EV charger amperage. The AI panel-photo analysis verifies the main breaker rating and the panel brand. The report returns the 220.83(A) calculated load against the service rating (NEC 230.79), with the 80 percent line reported separately as an advisory band, and shows 220.82 alongside it as one of five cross-check methods (220.82 binds instead when the homeowner is planning a full service change).

The 220.87 path itself belongs to your electrician: it needs a year of utility history (or a 30-day recording under the exception), and the report does not compute it. What the report does is show when it is worth pursuing. A result near the service rating is a reason to ask whether qualifying recorded demand and an AHJ-accepted 220.87 calculation are available, not a prediction that the result will pass.

The right framing: 220.83(A) is the default because it matches what a homeowner adding a load to an existing panel is actually asking, and it works without any input the homeowner does not already have. 220.87 is the upgrade path when utility data is available. It is a different permitted evidence path; the locally adopted code, documentation, and AHJ determine whether it can support the permit decision.

When 220.87 Triggers a Real Upgrade Conversation

The 220.87 method is not a guaranteed pass. There are houses where the actual recorded peak plus the EV charger exceeds the service rating, and the calc returns an honest no.

• All-electric house on a 100A service with a recorded peak above 65A. Existing demand at 125 percent already clears 80A - the 80 percent advisory comfort line on a 100A service - before the EV charger is even added, and it's the calculation against the 100A rating itself, NEC 230.79, that decides whether adding the charger still fits. On a house this tight, calculate rather than assuming the result. The EV may require a lower setting, listed load management, or a service upgrade. The heat pump on a 100A panel post walks the worked example.
• Two-EV household. The 220.87 calc on an existing one-EV house does not include the second EV in the recorded demand because the second EV has not been installed yet. The math has to add both EVs at 125 percent on top of the recorded peak, and the result frequently exceeds a 200A service. The fix is NEC 625.42 automatic load management on the EV side; the two-EV power-sharing post walks the 625.42 scope.
• FPE or Zinsco panel. 220.87 is a load calculation, not a panel-safety check. A Federal Pacific Stab-Lok or Zinsco panel needs to be replaced regardless of the calc result; the documented breaker-failure history is the trigger, not the load number. The FPE and Zinsco post walks the replace-do-not-add rule.

The Bottom Line

NEC 220.87 lets the electrician use real utility data instead of a calculated estimate to size an existing service for a new load. For an occupied dwelling with 12 months of utility history (or a 30-day recording under the exception), the math is existing demand at 125 percent, plus the new EV load, compared to the service rating. The result can be higher or lower than a calculated Article 220 result; the actual record and applicable code decide it.

The right workflow for an EV charger quote on a fully occupied house: run the applicable calculated method first—normally 220.83(A) or 220.83(B) for an existing dwelling—then ask whether 220.87 is accepted when qualifying data is available. A defensible quote names the method, shows its inputs, and follows the locally accepted permit path rather than automatically choosing whichever number is lower.

Run the $49 NEC Article 220 calc (220.83(A) binds for an existing home, 220.82 is shown alongside it as a cross-check), then hand the report to your electrician and ask them to run the 220.87 check against your utility's demand history. The report gives the quote its calculated numbers, and the 220.87 conversation keeps a conservative estimate from pushing a panel upgrade the real demand data does not support.