On this page
The lights go out at dinner time, and the fridge, the router and the porch light all stop at once. How does portable generator work? A small engine burns fuel to spin an alternator, and the alternator makes the power that runs the outlets on the panel. This guide follows the path from the fuel tank to the outlets, with figures from the listings, and ends with run time, noise and the safety rule that matters most.
SolarKitHQ earns a commission when you buy through links on this page, at no extra cost to you. As an Amazon Associate I earn from qualifying purchases. Affiliate disclosure.
The quick answer
A portable generator is a small engine bolted to an alternator. The engine burns gasoline, or propane on a dual fuel model, and the spinning crankshaft turns the alternator, which makes alternating current. The panel on the side hands that power to the outlets: household AC ports, a 12V DC port, and on some models a USB port or an RV port. An inverter generator adds a step in the middle, turning the alternator power into DC and back into clean AC, which suits laptops and phones.
How does portable generator work, step by step
These steps carry the power from the tank to the plug: fuel becomes motion, motion becomes power, power reaches the outlets, and ECO mode stretches the run time.
Step 1: Fuel becomes motion
It starts in the fuel tank. Gasoline feeds a small 4-stroke engine, the same kind of engine that runs a lawn mower, and the engine turns a crankshaft. The Westinghouse in the listings runs a 457cc 4-stroke OHV engine, and the Oxseryn 2800 (on Amazon) runs a 79.8cc 4-stroke OHV engine. The Westinghouse runs on gasoline or propane, so the fuel choice is the keeper’s, not the engine’s. A fuel gauge on the tank shows the level at a glance, and an automatic low oil shutdown stops the engine when the oil runs low, as the Westinghouse listing states.
Step 2: Motion becomes power
The crankshaft turns the alternator, and the alternator makes alternating current. On a plain portable generator that AC goes straight to the outlets. On an inverter generator it takes a detour: the alternator power is turned into DC, then an inverter turns it back into AC at a steady frequency, with total harmonic distortion under 3% on the listings here. That clean power is the point of the inverter models, and the PowerSmart listing states it can safely power delicate devices such as laptops, mobile phones and tablets. The Oxseryn 2800 states the same clean power figure, less than 3% THD, for phones, laptops, drones and cameras.
Step 3: Power reaches the outlets
The panel is where the power becomes useful. The Oxseryn 4400 (on Amazon) lists 2 120V AC ports, a 12V DC port and an RV port. The PowerSmart lists a 120V 20A duplex, a 120V 30A twist-lock, a 12V 8A DC port and dual 5V 2.1A USB ports. The Westinghouse lists two GFCI 120V 20A household receptacles, a 120V 30A transfer switch ready outlet and a 120/240V 50A RV ready outlet. Match the plug to the outlet, and match the load to the watts the listing states: running watts are the steady load, and peak watts are the short burst for starting a motor. A licensed electrician should install any connection from a generator to home wiring.
| Generator | Peak watts | Running watts | Run time |
|---|---|---|---|
| Oxseryn 4400 | 4400 | 3400 | Up to 14 hours at 25% load |
| Westinghouse 12500 | 12500 | 9500 | Up to 12 hours |
| PowerSmart 3800 | 3800 | 3200 | Not stated |
| Oxseryn 2800 | 2800 | 2000 | Up to 9 hours at 25% load |
The Westinghouse figures above are on gasoline. The same listing also states 8500 running watts and 11200 peak watts on propane.
Step 4: ECO mode and run time
A generator at light load does not need full engine speed, and ECO mode slows the engine down when the load is light. The Oxseryn 4400 runs for up to 14 hours at 25% load with ECO mode on a 2 gallon tank. The Oxseryn 2800 runs for up to 9 hours at 25% load on a 1.1 gallon tank. The Westinghouse runs for up to 12 hours on a full tank. Run time falls as the load rises, so the figure the listing states is tied to the load it states, and a full load empties the tank faster than a light one. The Oxseryn 2800 also lists a parallel function, which links two units, and the Westinghouse lists remote, electric and recoil start. See the best inverter generators for long run time for longer-running models.
Noise and size
The listings state noise as dBA from 23 feet: under 72 dBA for the Oxseryn 4400, 59 dBA for the PowerSmart, and under 58 dBA for the Oxseryn 2800. A lower figure means a quieter unit at that distance, and the PowerSmart and the Oxseryn 2800 are the quiet ones in this set. The weights run from 40 lb for the Oxseryn 2800 to 56 lb for the Oxseryn 4400, with the PowerSmart at 47 lb. A built-in handle and a compact frame make the smaller units easy to carry, as the listings state. See the best quiet inverter generators for models that run quiet.
Outdoors only
Fuel generators run outdoors only, far from doors and windows, because of carbon monoxide. The PowerSmart listing states it plainly: never use a generator indoors or in partially enclosed areas, and only use it outdoors. Keep the unit on dry, level ground with clear air around it, and never run it in a garage, a shed or under a covered porch. At altitude, the Oxseryn 2800 listing recommends a high-altitude kit above 4000 feet, about 1200 meters, and warns that without the adjustment the generator may run rough, use more fuel, or be harder to start.
FAQ: power away from the grid
How much power does a portable generator make?
The listings here run from 2000 running watts on the Oxseryn 2800 to 9500 running watts on gasoline on the Westinghouse, with peak watts above each figure. Check the running watts first, since that is the steady load the unit can carry.
Can a portable generator run a laptop?
Yes, on an inverter model. The PowerSmart and Oxseryn 2800 listings state clean power with THD under 3% for delicate devices such as laptops, mobile phones and tablets. A plain portable generator without an inverter still makes power, but the listings here do not state the same clean power figure for it.
How long does a portable generator run on a tank?
The listings state up to 14 hours at 25% load for the Oxseryn 4400, up to 12 hours for the Westinghouse, and up to 9 hours at 25% load for the Oxseryn 2800. The tank size and the load set the figure, so read the run time with the load the listing states.
Can I use a portable generator indoors?
No. Use it outdoors only, as the PowerSmart listing states, never indoors or in partially enclosed areas. Keep it far from doors and windows.
What is the difference between running watts and peak watts?
Running watts are the steady load the generator can carry. Peak watts are the short burst for starting a motor. The Oxseryn 4400 states 3400 running watts and 4400 peak watts, so the peak figure sits above the running figure on the same unit.
Related solar guides
See the power stations guides, the best inverter generators for home backup, the benefits of an inverter generator and the dual fuel vs gas generators.
