Tools do not behave like appliances
Every other page on this site sizes for loads that run steadily. Tools do the opposite, and it changes the arithmetic completely.
- Enormous surge, brief. A universal motor spinning up under no load draws several times its running figure for a fraction of a second — the same mechanism as a compressor start, but happening dozens of times an hour.
- Tiny duty cycle. A circular saw runs for four seconds a cut. Across an hour it may draw power for three minutes.
- Unpredictable coincidence. Nobody coordinates. Two trades start two tools in the same second and the peak doubles.
So: size on the surge, budget fuel on the duty cycle. A machine that handles the biggest tool plus margin will use far less fuel than its rating suggests, because it spends most of the day at near-idle.
Typical tool draws
| Tool | Running watts | Starting watts |
|---|
| Circular saw, 7¼ in | 1,400 | 2,300 |
|---|
| Air compressor, 1 HP | 1,600 | 4,500 |
|---|
| Miter saw, 10 in | 1,800 | 1,800 |
|---|
| Reciprocating saw | 960 | 960 |
|---|
| Electric drill, ½ in | 600 | 900 |
|---|
| Battery charger | ~100 | — |
|---|
| Work light, LED | 20-100 | — |
|---|
Tool figures are Champion Power Equipment's published ranges from the same wattage chart used across this site. Charger and LED light rows are working estimates from typical equipment ratings. Your tools' own nameplates are the figures that count, and a well-used tool draws more than a new one.
The marked row is the one that sizes the machine. A 1 HP compressor at 4,500 starting watts is larger than any two hand tools together, and it cycles on its own schedule rather than yours.
Waveform matters more on a site than at home
Cordless tool chargers, laser levels and laptops all contain switch-mode power supplies, and a dirty waveform from a cheap conventional generator can damage them or refuse to charge at all.
An inverter generator publishes total harmonic distortion — the Westinghouse iGen2200 quotes under 3% — and that specification is the difference between a machine that charges a van full of batteries reliably and one that quietly kills chargers.
If the site load is only resistive — lights, heaters, a corded drill — a conventional machine is fine and cheaper. The architecture comparison covers the trade.
What a job site adds that a house does not
Working under OSHA construction standards changes the rules, and the answers differ from the residential ones on this site.
- GFCI protection is required for receptacle outlets on construction sites, either through GFCI devices or an assured equipment grounding conductor program.
- Cords are inspected, not assumed. Damaged insulation and missing ground pins are among the most cited electrical violations there are.
- Grounding follows the regulation. For cord-and-plug use, OSHA 1926.404(f)(3)(i) permits the bonded generator frame to serve as the grounding electrode — the grounding page covers the detail, but on a site take the answer from the regulation and your site safety plan rather than from a consumer guide.
- Carbon monoxide risk rises indoors. Generators inside partially enclosed structures kill workers every year. Outside, twenty feet, exhaust away.
Noise is a scheduling constraint
On residential work it is not a comfort question — it is whether you can start at seven.
Many municipalities set construction noise hours, and a complaint can stop work for a day. An enclosed inverter at 53 dBA measured from 23 feet is a different proposition from an open-frame machine at close to 70 dB, and because decibels are logarithmic that gap is much wider than it looks.
Security, which nobody plans for
Generators are among the most stolen items on a site, and an unattended one overnight is a target.
- Chain it to something structural, not to a fence panel.
- Take it in overnight where you can. A 39 lb inverter goes in the van; a 200 lb open-frame machine does not.
- Mark it. Engraved identification makes resale harder and recovery possible.
- Propane is harder to steal than gasoline, which is a small but real argument for dual fuel on an unsecured site.
Batteries have taken over part of this job
Worth being honest about how much the category has changed. Cordless platforms now cover most hand tools, which means a lot of sites need power for chargers rather than for tools.
That is a much smaller load — roughly 100W per charger — and it is steady rather than surging. A kilowatt-hour battery charges a van full of packs across a day, silently, indoors, with no fuel.
The generator then becomes the thing you bring out for the compressor, the table saw and the concrete work, rather than the thing that runs all day. That split is cheaper, quieter and better for the neighbors than one machine idling from seven to five.
The general comparison applies, with the site-specific difference that the surge loads here are genuinely beyond any portable battery.
