Run a generator for power tools only when the job would take ten times or more longer by hand, you can spare the fuel, and the generator can sit outdoors in a ventilated, secure spot, because its exhaust contains deadly carbon monoxide and its noise carries. For routine battery charging, a 100-200 W solar panel with a charge controller and a battery bank supplies tool power with no fuel and no noise.
Part of Tool Identification & Repair
A generator turns fuel into tool power at a price that matters in a world with no resupply, while a solar panel turns sunlight into the same power at no ongoing cost but a much slower rate.
A Generator Is A Fuel-To-Work Converter, So Spend It On Work That Counts
The parent article gives three conditions for running a generator for power tools: the task would take ten times or more longer by hand (cutting steel, drilling concrete); you have fuel to spare and a secure, ventilated location; and the noise will not attract unwanted attention, since generators are loud at 65-90 dB.
Fuel use is the other limit. The parent article gives a typical 2000 W inverter generator as burning 0.5-1 litre per hour at 50% load. A cordless tool charger draws 50-200 W, so running a generator solely to charge batteries is wasteful: charge several batteries and run other loads at the same time.
What You Need
- A generator with its own fuel supply, kept outdoors and on level ground.
- Heavy-duty extension cord rated for the load, kept as short as possible.
- Fire safety gear: sand and a Class B extinguisher if available.
- For solar: a 100-200 W panel, a charge controller and a battery bank (even a car battery); see Charge Controller.
- A carbon monoxide-safe layout: a spot well away from doors, windows and vents.
Method: Batch The Jobs, Then Run The Generator Once
Step 1: Decide. Apply the ten-times test and the fuel test from Power Tools Without Power. If either fails, use hand tools or solar.
Step 2: Gather every load you can run in one session: tools, battery chargers, a vehicle battery on charge. Running several loads together avoids burning fuel for one small one.
Step 3: Site the generator. Place it outdoors, downwind of the living area, away from windows and doors, in a spot protected from rain. Do not run it in a garage or shed, even with the door open.
Step 4: Fuel it cold. Stop the engine and let it cool before refuelling, and fuel on the ground, away from the exhaust. See Fire & Vapor Safety.
Step 5: Run it, work, then shut it down. Do not leave it idling between jobs.
Step 6: Solar for the rest. A 100-200 W panel with a charge controller and battery bank gives indefinite tool charging with no noise and no fuel (parent article).
Worked Example
A 2000 W generator at 50% load supplies 2000 × 0.5 = 1,000 W. At the parent article’s 0.5-1 litre per hour, one hour delivers 1,000 Wh for 0.5-1 L, so about 1,000 to 2,000 Wh per litre at that load. A charger drawing 100 W is only 100 ÷ 2000 = 5% of the generator’s capacity, far below the 50% the figure applies to, so fuel use per watt-hour will be worse than the range above. That is the arithmetic behind running the generator only for charging being wasteful.
Common Mistakes
- Running the generator for one small charge. The fuel cost per watt-hour is high at low load.
- Placing it close to a window or door. Exhaust enters the building.
- Refuelling a hot or running engine. Spilled fuel meets a hot surface.
- Ignoring noise. It carries a long way and tells people where you are.
- Plugging a generator into house wiring. It can energise lines outside the building.
Safety
Carbon monoxide kills without warning, and generator fuel burns
Generator exhaust contains carbon monoxide, which is colourless and odourless; never run a generator indoors, in a garage, or near an open window or door. See CO Risk. Refuel only when the engine is stopped and cool, keep fuel containers away from the exhaust, and never test for fuel vapour with a flame. Keep cords out of water and do not connect a generator to a building’s wiring.
What’s Next
- Learn next: Cordless Tool Battery Management — using the power you generate
- Combine with: Manual Alternatives to Power Tools — the jobs that never need a generator