Updated March 2026 | By ToolShed Tested Team
Quick Answer: For running one power tool at a time, a 3,000-4,000 watt generator handles most tools including circular saws and miter saws. For running multiple tools simultaneously on a job site, you’ll need 5,000-7,500 watts. Always size for starting watts, which can be 2-3x the running watts for motor-driven tools.
Understanding Generator Sizing for Power Tools
Running Watts vs. Starting Watts
Every motor-driven tool requires a surge of power to start spinning. This starting wattage (also called surge or peak watts) can be 2-3 times the running wattage (continuous watts). Your generator must handle the starting surge, or the tool won’t start—or worse, the generator’s breaker will trip.
- Running watts: The power the tool needs while operating at steady speed
- Starting watts: The momentary spike when the motor first engages
Power Requirements by Tool
| Tool | Running Watts | Starting Watts |
|---|---|---|
| Circular saw (7-1/4″) | 1,400-1,800 | 2,400-3,500 |
| Miter saw (10-12″) | 1,200-1,800 | 2,400-3,600 |
| Table saw (10″ contractor) | 1,800-2,500 | 3,500-5,000 |
| Corded drill | 400-800 | 600-1,200 |
| Reciprocating saw | 1,000-1,500 | 1,500-2,500 |
| Router | 1,000-1,800 | 1,500-3,000 |
| Air compressor (1-2 HP) | 1,000-2,000 | 2,000-4,000 |
| Grinder (4-1/2″) | 900-1,400 | 1,400-2,500 |
| Shop vacuum | 600-1,400 | 900-2,000 |
Sizing Guide by Use Case
Scenario 1: One Tool at a Time (DIY / Remote Projects)
Recommended: 3,000-4,000 watts
If you’re running a single tool and maybe charging a phone or running a light, a mid-size portable generator is sufficient. A 3,500-watt generator starts a circular saw comfortably and runs it with headroom to spare.
Scenario 2: Small Job Site (2-3 Tools)
Recommended: 5,000-6,500 watts
Running a miter saw, a shop vacuum, and charging cordless batteries simultaneously requires more capacity. Add up the running watts of all tools plus the starting watts of the largest one.
Scenario 3: Full Job Site (Multiple Tools + Compressor)
Recommended: 7,500-10,000 watts
A contractor running a table saw, compressor, multiple plug-in tools, and lights needs serious capacity. Consider a 240V generator if running a cabinet table saw with a 240V motor.
How to Calculate Your Needs
- List every tool and device you’ll run
- Write down each tool’s running wattage (check the nameplate or manual)
- Identify the tool with the highest starting wattage
- Add: (all running watts) + (highest starting watts – that tool’s running watts) = minimum generator size
Example: Miter saw (1,500 running / 3,000 starting) + shop vac (1,000 running) + lights (200 running)
Total = 1,500 + 1,000 + 200 + (3,000 – 1,500) = 4,200 watts minimum
Inverter vs. Conventional Generators
- Inverter generators: Clean power (safe for electronics), quieter, fuel-efficient, lighter—but more expensive per watt. Best for smaller setups.
- Conventional generators: More watts per dollar, noisier, heavier. Better for dedicated job sites where noise isn’t an issue.
FAQ
Can I run cordless tool chargers on a small generator?
Yes. Most cordless tool chargers draw only 100-300 watts. Even a small 1,000-watt inverter generator can charge multiple batteries at once. This is a good option for remote work if you already own cordless tools.
What about the wattage on the tool’s nameplate?
Nameplates usually list running amps at 120V. Multiply amps × volts to get running watts (e.g., 15A × 120V = 1,800W). Starting watts are typically 2x this number for universal motors and 3x for induction motors.
Do I need a surge protector between the generator and my tools?
For standard corded power tools, no. For sensitive electronics (laptops, battery chargers with microprocessors), an inverter generator or a surge protector is recommended to protect against voltage spikes.