Portable Generator
A portable generator is an engine-driven power source built to be moved to the work, carried, wheeled, or loaded in a truck, and to feed tools, lighting, and equipment through onboard receptacles. The class centers on gasoline and small diesel units in the low-kilowatt range, the workhorse power source for crews operating away from grid service.
Cat classes
Pick a size class: capacity and reach differ across the range.
How it works
An engine drives an alternator at governed speed to hold 60 Hz output, with a voltage regulator maintaining output at nominal receptacle voltages. Loads plug directly into the panel: duplex receptacles for cords and tools, and twist-lock outlets for higher-current connections on larger units. Output is quoted as running (rated) watts and a higher surge figure for motor starting. Conventional units hold full governed speed whenever running; the class's larger wheeled members trade the refinement of inverter units for simpler construction and higher output per dollar.
Types & variants
- Recoil-start frame units
- Open-frame gasoline generators at the small end, hand-carried or two-person lifted, serving hand tools and lighting.
- Wheeled jobsite units
- Mid-size frame generators with wheel kits and lifting bails, the standard crew power source in the 3-7 kW class.
- Electric-start units
- Larger portables with battery start and often twist-lock receptacle panels for feeding subpanels or trailers.
- Small mobile diesel units
- Compact diesel-powered generators bridging toward the towable class, favored where diesel fuel is already on site.
Key specifications
| Specification | Typical range | What it means |
|---|---|---|
| Power output | 5.0-560.0 kVA | Running watts govern what operates simultaneously; the surge rating must cover the largest motor start. |
| Fuel capacity | 3.2-385.0 gal | Tank size against load level sets refueling intervals during a shift. |
| Fuel consumption | 0.7-33.1 gal/hr | Consumption scales with load; planning fuel for a shift means estimating average load, not nameplate output. |
| Engine power | 5.7-2220.0 hp | Engine horsepower drives alternator output and determines the unit's continuous rating. |
How the industry sizes it
The portable class is sized in kilowatts. Cataloged portable units group into bands: up to 3 kW, 3-7 kW, 7-12 kW, and 12+ kW. Selection sums the running watts of everything operating at once, adds the largest starting surge, and lands on the smallest unit that covers the total: oversizing wastes fuel and buys unnecessary weight.
Applications
- Tool and cord power for crews on unpowered sites
- Temporary lighting and small-equipment power
- Backup power for homes, farms, and small commercial spaces
- Powering pumps and heaters on service and maintenance work
- Event and vendor power at the small end of the class
- Supplementing site power at locations distant from the main generator
Safety & operation
- Operate outdoors only, away from doors, windows, and vents: CPSC guidance is at least 20 feet from occupied structures; portable generators account for the majority of carbon monoxide deaths tied to consumer products.
- Models with CO-sensing shutdown (built to UL 2201 or equivalent) add a critical layer of protection; the sensor must never be bypassed.
- Never backfeed a building through a receptacle; connection to premises wiring requires a transfer switch or listed interlock.
- Use GFCI protection for cord-connected tools, and elevate connections out of standing water.
- Shut down and cool before refueling; gasoline spilled on a hot muffler is a fire cause on small generators.
Standards & certifications
- UL · UL 2201
- Standard for carbon-monoxide-mitigating portable generators.
- NFPA · NFPA 70 (NEC), Articles 445 and 702
- Generator installation and optional standby connection requirements, including transfer equipment.
Frequently asked
What is the difference between running watts and surge watts?
How does a portable generator differ from an inverter generator?
Can a portable generator power a building during an outage?
Why does the class data show units far larger than hand-portable sizes?
Compare popular models
Find by spec →Normalised to the same units. A dash means the figure was not published.
| Model | Power output | Fuel capacity |
|---|---|---|
| Allmand Maxi-Power 25 | 25.0 kVA | 52.0 gal |
| Multiquip DA7000SSA3 | 9.3 kw | 6.6 gal |
| Multiquip DAC7000SSA3 | 6 kw | 28.0 gal |
| Multiquip DCA10SPXU4C | 18.3 kw | 28.0 gal |
| Multiquip DCA15SPXU4F | 18.3 kw | 28.0 gal |
| Wacker Neuson G25 | 37 kw | 62.6 gal |
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Sources
Every specification is verified against the manufacturer's published data, with the source linked for reference.