Why people use generators
Away from a reliable outlet, such as at a remote build site, in a field or during a power outage, a portable generator can run corded tools, lights and chargers. A small gasoline engine turns an alternator that produces household-style power. Generators are useful, but they are also associated with serious hazards when used carelessly, and the most serious one is carbon monoxide.
Treat this article as general background. The manual for your generator and your local rules are the authority.
Carbon monoxide and ventilation
Gasoline engines produce carbon monoxide (CO), a gas you cannot see or smell that can incapacitate or kill quickly in an enclosed space. Several points apply generally:
- Run a generator outdoors only. Do not run it in a garage, basement, shed, crawl space or tent, even with the door open or a fan running.
- Keep it well away from windows, doors and vents. Fumes can drift back into a building. Manuals usually specify a minimum distance, and the exhaust should point away from occupied spaces.
- Do not place it where exhaust can collect, such as in a covered area with poor airflow.
- Use battery-powered carbon monoxide alarms in nearby indoor spaces when a generator is operating at a home.
- Know the symptoms. Headache, dizziness, nausea and confusion can be warning signs. Anyone who feels unwell should get to fresh air and seek medical help.
The same caution applies to other fuel-burning equipment, and it is one of the reasons many people weigh the trade-offs of gas-powered tools against electric ones.
Sizing: running watts and starting watts
Generators are rated with running (rated) watts and a higher starting (surge) rating. Motors need extra power for an instant at startup, so a generator has to cover the starting surge of the biggest motor as well as the running load of everything else.
A hypothetical example: say a saw draws 12 amps at 120 volts when cutting, which is 1,440 watts (12 x 120 = 1,440), and a work light uses 100 watts. Running together, that is 1,540 watts before allowing for the startup surge of the saw’s motor. A generator that barely meets that number on paper may struggle in practice, and one with real headroom will tend to run more steadily. Tool amperage on the nameplate gives you a starting point, and tool manuals may include guidance on generator use or minimum power.
Some considerations when sizing:
- Add up the running watts of everything you plan to operate at once.
- Allow extra for the largest motor’s starting surge, especially for compressors and stationary saws.
- Leave margin rather than running at the maximum rating.
- Check whether the manual for your tool warns about generator power quality. Some electronics and battery chargers prefer clean, stable output, and the generator’s documentation may describe this.
An undersized generator can stall, overheat or produce unstable voltage, which stresses motors. A large air compressor is a common example of a load that can overwhelm a small unit.
Fuel and engine safety
- Turn the generator off and let it cool before refueling. Fuel spilled on hot parts can ignite.
- Store fuel in approved containers, away from living spaces, heat sources and ignition sources.
- Keep the unit on a stable, level surface, and keep it dry. Rain and wet ground are hazards. A manufacturer-approved cover or canopy designed to leave the exhaust clear is safer than improvised shelters.
- Generators are loud. Hearing and dust protection is worth wearing close to the unit for extended periods.
- Follow the manual for oil checks, maintenance and break-in.
Connecting tools safely
Plug tools into the generator’s outlets using appropriately sized cords. Avoid long, thin cords, which cost you voltage. The generator’s outlets and the cords you use should be in good condition, and a cord with bad insulation is more dangerous in damp field conditions.
Many generator manuals describe grounding procedures and whether the unit should be grounded to a stake. These vary by model and by local rules, so follow the manual. Outlets with ground fault protection, or portable GFCI adapters, are commonly recommended for outdoor and wet conditions, and the electrical safety equipment you carry could reasonably include them.
Never connect a generator to a house through an outlet or by “backfeeding.” Feeding power into a building’s wiring without proper equipment can send electricity back to the utility lines, endangering line workers, and can create fire and shock hazards at home. If you want a generator to power parts of a house, ask a licensed electrician about a transfer switch or an interlock designed for that purpose and permitted locally.
Alternatives and everyday judgment
For a few small tools, battery-powered models or a power station with an inverter may be options, avoiding exhaust. For larger demands, a generator makes sense, but it should be an informed choice about noise, fuel, maintenance and ventilation rather than a convenience reached for in a hurry.
Before you start, check the area, keep the generator outdoors and away from openings, confirm that cords and plugs are sound, and unplug a tool before changing its blade or bit as you would anywhere else. If you are unsure about any part of a setup, stop and get qualified advice. Outcomes in electrical and fume hazards can be severe, so conservative habits are justified.