A service is sized for the current it carries at its busiest moment, and part of that current often does no useful work. We measure where it goes, specify the changes that return it, and measure the panel again so the result stands on a sealed document.
86 kVA returned to the service, and the new load fits.
Cables, breakers and transformers are rated for current and the heat it produces. The limit that matters is the current a facility draws at its busiest moment, and that current has three parts. Only the first is doing the work the facility exists for.
Lawrence Berkeley National Laboratory and NREL have documented how much commercial equipment keeps running when nobody needs it. The share that occupies capacity is the share still running at the peak, and it comes from five sources.
The affinity laws for fans and pumps, ASHRAE Handbook. Power scales with the cube of flow, so 80% of full airflow needs 0.8 × 0.8 × 0.8, or 51%, of full power.
This part of the current delivers almost no energy, so an energy audit rarely finds it. It still occupies the rating, because a service carries amperes whether or not they do any work.
A worked calculation, apparent power equals real power divided by power factor. It describes no particular facility. Capacitor application follows IEEE Std 1036.
Motors and transformers draw current that lags the voltage and hands its energy back every cycle. The service carries it all the same. A facility drawing 456 kW at a power factor of 0.82 presents 556 kVA to its service. Corrected to 0.97, the same 456 kW presents 470 kVA, and 86 kVA of the rating comes back with no change to the work being done.
Because correction saves almost no energy, efficiency programs seldom pursue it. On a service that is short of capacity, it is one of the most direct changes there is.
Drives, LED drivers, chargers and switch-mode power supplies draw current in short pulses. That distortion adds to the true current in every cable and breaker and adds heat in transformers, so a transformer feeding these loads can carry less than its nameplate. IEEE Std C57.110 sets out how far to derate it. In a four-wire system the third harmonic from single-phase electronics adds up in the neutral, which can end up carrying more current than any phase.
Electrification adds exactly these loads, so we measure the harmonic baseline before anything is added. It is also measured before any capacitor is fitted, because capacitors on a distorted supply can resonate with it (IEEE Std 519).
A three-phase service is full when its busiest phase is full. Single-phase circuits landed unevenly leave room on two phases while the third reaches its limit. Moving circuits between phases needs no new equipment and returns the gap between the heaviest phase and the average. Unbalanced voltage also derates three-phase motors, as NEMA MG 1 describes.
A service is sized for its peak. Lower the peak and the same service carries more.
NEC 220.87 sets the existing load from the recorded peak, so a verified reduction counts in the calculation.
Wattif performs no electrical work. A licensed electrician makes every change, and we measure the result.
Recoverable current identified circuit by circuit from a 4 to 8 week instrumented window, in kilowatts and in amperes. Each change is specified by what it has to achieve: schedules, staging, drive speeds, setpoints, power factor correction and phase moves. The choice of product stays open.
A licensed electrician performs the work to the specification. We schedule it, we answer to it and we accept it against the spec.
The same panel measured again with the same instruments in the same positions, normalised for weather against the baseline. The recovered kilowatts and amperes are stated at the measured peak.
None of the sources on this page can be assumed for a given facility. A well-run site may carry no wasted power and still draw more current than its work needs, while a site with clean power may run its exhaust fans all night. The first task of the determination is to find out which facility it is looking at.
When the useful load on its own exceeds the service rating, no recovery is enough. The determination says so, and the upgrade is then designed against a measured basis.
An upgrade may still be the right answer. The decision to make one should follow a measurement.
