Planning guide
Temporary power keeps tools, trailers, and lighting running — and it’s also one of the most safety-critical systems on a site. This guide covers how power gets sized, the code and safety rules that apply, and how to distribute it safely. Final sizing and connections are always confirmed by a qualified electrician.
Sizing temporary power begins with a load list: every tool, trailer, light tower, heater, pump, and piece of equipment that could run at the same time, with voltage and amperage wherever you know it. Add up what runs concurrently — not the total of everything you own — to get your running load.
Here’s the detail that trips up most do-it-yourself sizing: motors, compressors, and pumps pull a large surge of current the instant they start — often several times their running draw. A generator sized only to the steady running total will sag or stall the moment a big motor kicks on. Proper sizing builds in headroom for those startup surges, which is a key reason a qualified provider or electrician confirms the final number.
Temporary power on a jobsite is governed by NEC Article 590 and OSHA. Among the core requirements:
Distribution panels and spider boxes provide code-compliant, GFCI-protected outlets — the safe alternative to daisy-chained extension cords.
Getting power from the generator to the work means planning drop points: where panels and spider boxes sit, how cable is routed, and where crews actually plug in. Mapping this up front keeps power close to the work and avoids a tangle of cords across walkways and driving lanes. Think about the busiest work areas, overnight needs, and anywhere water collects.
Generators need a plan for runtime and refueling. Note your operating hours, whether anything runs overnight, and any fuel or noise constraints on the site. Placement matters too — generators need ventilation and clearance, and should sit where exhaust and noise won’t affect occupied spaces or neighbors.
Temporary power often feeds the equipment around it: light towers for night work and staging yards, heaters for cold-weather pours, curing, and drying, and spot coolers or fans for hot enclosed spaces. Each adds to your total load, so include them in your list up front rather than bolting them on after the generator is sized.
Electrical sizing and connections are a safety matter and are always confirmed by a qualified provider or licensed electrician before anything is finalized.
List trailers, tools, lighting, pumps, and any known voltage, amperage, phase, or wattage — including what starts at once.
Share operating hours, overnight requirements, fuel constraints, and placement for ventilation.
Capture cable paths, drop points, protected areas, and site constraints for qualified setup review.
Tell SITE PRO what your project needs — sanitation, fencing, dumpsters, a site office, power. One request, one point of contact, and rough numbers are fine to start.
