Headroom

For people electrifying facilities the grid wasn’t ready for.

FEATURED FIELD GUIDESep 13, 7 minWhat is NEC 220.87?NEC 220.87 is the method for establishing the existing load on a service or feeder from what it actually drew: the maximum demand over 12 months of utility records, or a 30-day recording where those are not available, taken at 125% and added to the new load against the rating. In the 2026 edition the same method is numbered 120.87.Read the guide →

THE EVIDENCE12 months, or 30 daysTHE INTERVAL15 minutesTHE ANSWERFits, tight or short

FIELD GUIDESep 14, 3 minCan my panel handle a new tenant?The house meter sees the whole facility; the tenant lives on one panel. So the question has two parts: whether the service has room, which 12 months of the landlord's demand records answer under NEC 220.87, and whether the feeder to the suite has room, which those records cannot see and a 30-day recording on that feeder can. The new load is counted per its own article, and a kitchen is the case the code is kindest to.FIELD GUIDESep 14, 3 minCan my panel handle a heat pump?Usually the question is whether it can handle the heat pump and its backup heat at the same time. Under NEC 220.87 the existing measured demand at 125%, plus the heat pump counted at its nameplate rated-load current under Article 440, has to fit under the service rating. Heating and cooling on the same unit are counted once, but electric backup that can run with the compressor is counted with it.FIELD GUIDESep 14, 3 minCan my panel handle EV chargers?It depends on what the service actually draws today, which a measurement establishes and a calculation only guesses at. Under NEC 220.87 the existing measured demand at 125%, plus the chargers counted the way Article 625 and 220.57 require, has to fit under the service rating. An energy management system can make a bank of chargers fit where their nameplates summed would not.JURISDICTIONSep 13, 3 minDoes a load calculation need a PE stamp in California?It depends on who is installing the work and what the authority requires. Electrical engineering is a practice act in California, a licensed contractor may design only the electrical work it installs itself, and the authority reviewing the permit sets whether the calculation has to be sealed. The NEC itself requires no stamp.JURISDICTIONSep 13, 2 minIs it NEC 220.87 or 120.87 in California?It is 220.87. The 2025 California Electrical Code, Title 24 Part 3, is based on the 2023 NEC and took effect on 1 January 2026. The 2026 NEC renumbers the method to 120.87, and that number applies in California only when the state adopts the 2026 edition through a future code cycle.JURISDICTIONSep 13, 5 minHow do load studies work in California?California is on the 2025 California Electrical Code, based on the 2023 NEC and in force since 1 January 2026, so the measured-load method is section 220.87. Electrical engineering is a practice act there, a licensed contractor may design only what it installs itself, and all three investor-owned utilities run service upgrades under Electric Rule 16.FIELD GUIDESep 13, 3 minWhat is demand on a commercial electric bill?Demand is the highest rate at which the facility drew power during the billing period, in kilowatts, averaged over an interval the utility sets, commonly 15 minutes. Consumption is the energy used over the whole period, in kilowatt-hours. A load study needs demand, because the peak is what sizes a service, and a bill that shows only kilowatt-hours cannot supply it.FIELD GUIDESep 13, 3 minWhat is the difference between a load calculation and a load study?A load calculation establishes the existing load from what could run, using the demand factors in Article 220. A load study establishes it from what the facility actually drew, using NEC 220.87. Both are recognised by the code. The study usually shows more room, because the calculation assumes far more of the equipment runs at once than ever does.FIELD GUIDESep 13, 3 minHow long does a load study take?3 days from 12 months of utility records, and about 5 weeks where the panel has to be metered, because 30 days of readings are the evidence. The turnaround is published and it is the same for every customer.FIELD GUIDESep 13, 2 minDoes a load calculation need a PE stamp?The NEC does not require one. Whether your submittal needs a Professional Engineer's seal is set by the authority having jurisdiction and by state licensing law, so it depends on where the facility is and what the permit is for. Ask the authority before you submit.FIELD GUIDESep 13, 3 minLoad study or service upgrade?Get the load study first. It tells you whether the upgrade is needed at all, and if it is, the study becomes part of the upgrade application. It is the cheaper and faster step, and it is never wasted.

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