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Power Tools: How Much Power Do They Need?

Power tools have big appetites. The moment you turn them on, they gobble up more than their fair share of electricity. As a result, you have probably tripped a few circuit breakers in your shop while feeding your power tools. To ensure you have an adequate power supply for your hungry power tools, it may be best to take a look at wiring.

How much power do my tools need?

Tools are fueled by amps. To check how much yours need, check the nameplate located on the tool’s body or motor housing. Look for information about AMPS and VOLTS. Make a list of the amps consumed by each tool. Also, make note of any tools that can be wired to run on 240 volts instead of the standard 120.

The typical amperage for small power tools (sander, jigsaw, etc.) is 2 to 8 amps. For larger power tools (router, circular saw, tablesaw, lathe etc.), 6 to 16 amps is typical. Some tools such as duct collectors and air compressors may need even more power.

Do I have enough power to draw from?

Most homes built in the last 40 years or so have 100- to 200-amp service. This should be plenty of power to run a modern household and a shop. Consider having an electrician install a subpanel in your shop so you don’t have to share circuits with the house. This allows for shorter wiring, which decreases power loss and heat buildup, and also gives you the option to shut off power to the shop when not in use.

If your home was build pre-1950, and you haven’t made any electrical updates, you probably only have 60-amp service. You should look into having your service increased and a new panel installed to prevent tripping breakers when operating power tools.

How should I size my circuits?

Start by examining the list you made of your tools’ amperage requirements. Keep in mind that electrical codes require a load on a circuit not to exceed 80 percent of its capacity. This means if you want to run a 16-amp tablesaw, you need a 20-amp circuit. If you ever run two high-power tools at the same time – such as a tablesaw and dust collector – you need two separate circuits to handle the load.

Should I rewire to 240 volts?

Doubling the voltage from 120 to 240 volts cuts the amperage use in half. This means you can run a 14-amp tablesaw and 12-amp dust collector at 13 amps instead of 26, allowing you to run both tools on the same 20-amp, 240-volt circuit. Of course, when pushing your power limits, don’t forget about non-tool items in your shop, such as lights and heaters.

Contrary to common belief, running a power tool on 240 volts instead of 120 doesn’t make it more powerful because, since the amp use is cut in half, the wattage stays the same. For example, a 16-amp power tool on a 120-volt circuit draws 1,920 watts (16x120=1,920). That same tool on a 240-volt circuit now runs at 8 amps and still consumes 1,920 watts (8x240=1,920).

However, you may notice a power difference if you had been running an 18-amp tool on a 20-amp circuit. Switching to 240 volts decreases the load to 9 amps out of 20 available, which ensures the motor remains at full throttle.

Unless you’re a skilled electrician and familiar with local building codes, rewiring your home or shop is a job you should leave to a professional. Contact Mr. Electric® and use the information you learned here to guide the conversation toward upgrading your circuits to match your needs.