Shop Power

The electrical power used for corded power tools can be very dangerous. Wiring within your shop or garage should be done by a licensed electrician. You should follow all manufacturer's warnings and recommendations regarding plug wiring, extension cords, and the use of power. If they recommend something different from what you find on Toolcritic.com, follow their recommendations.

There are three types of power requirements for the tools you'll find on Toolcritic.com: single-phase 110VAC, single-phase 220-240VAC, and three-phase 220-240VAC (some of which can be wired for 440-480VAC). You need to consider the power requirement of the tool before you purchase it and either get a version of the tool that uses the power supplied by your shop or consider upgrading your shop.

110VAC

110-120VAC is the voltage you'll find coming out of every standard outlet in North American houses and businesses. The plugs are standard and vary only in whether there is a center ground pin. Virtually all hand-held power tools and many stationary tools use 110VAC.

Amperage

The amperage rating of a power tool determines the amount of power that it uses. The higher the amperage rating, the faster the tool is going to turn the little dial in your electrical meter. If you have two tools of equal voltage and one has a higher amperage rating, its motor will use more power and tend to generate more torque (circular force) than the lower amperage tool. (although one tool may be more slightly more efficient than another even though the amperage ratings are identical).

If you try to push too many amps through a wire, resistance in the wire will make it heat up. Thicker wires offer less resistance than thinner wires. The wires in your walls are protected from overheating by circuit breakers or fuses that limit the amount of power that can flow through them. Check your electrical box to see the ratings of your circuits. Typical 110VAC home outlets are rated at 15 or 20 amps.

Take a look at the amperage requirements of the tool and check it against the circuit you plan to use. You can't use a tool that will require 20 amps in a 15 amp circuit. Also remember that amperage requirement is additive. If you have a dust collector that's using 15 amps and a table saw that uses 15 amps that's a total of 30 amps. If you plan to run them at the same time, you'll need to run them on different circuits. Remember that there are often multiple outlets on a circuit so moving one outlet over may not be sufficient.

Voltage

There is a wonderful analogy of water in a pipe that is often used to describe electrical power. Frankly, the math seems easier to understand than the water. The power used by a tool is the product of the voltage and the amperage or current (P=VI). If you double the voltage from 110VAC to 220VAC, you can deliver the same amount of power using half of the amperage. A table saw that might require a 40 amp circuit using 110VAC would only require a 20 amp circuit using 220VAC (Power = 40amp x 110V = 20amp x 220V). The advantage of the higher voltage is that as the amperage requirement is reduced, so is the resistance in the wire. Smaller wires are required for higher voltages.

Extension Cords

The longer an extension cord is and the smaller its wire, the more resistance to current flow it will create in the circuit. As the amperage rating of the tool increases, the size of the wire needs to increase. The wire's gauge determines its size. Smaller numbered gauges are thicker than larger numbered gauges. For example, a 10 gauge wire is thicker than a 12 gauge wire (only even sizes are manufactured).

The rule of thumb is that for each 100 feet of extension cord, you need to use the next larger gauge wire. A tool with a 16 gauge cord will usually require at least a 14 gauge extension cord if it is 100 feet long. Try to use the shortest extension cord possible, especially for stationary tools. Voltage drop will occur if the wire size is too small or the extension cord is too long and that can reduce the effectiveness of the tool or damage it. Look at and follow the manufacturer's recommendations for extension cords.

220VAC

To deliver more power to larger tools, motors are wired for 220VAC. Most houses in North America have 220V coming into the house at their box. The power is split into two 110V wires which combine for 220V.  The common (white) wire is replaced by a second 110V wire (usually red or black). The two hot wires allow twice as much power to be delivered with the same size wire. You probably have an oven, air conditioner, or dryer that is using 220V now.

It's the Wild West when it comes to 220V plugs. There are at least four standard plugs in the US and others internationally. Most of the 220V tools we've purchased have come without a plug. We go down to our local home improvement store and buy a plug that matches our outlets and wire it ourselves. Some of our 220V tools are directly wired (no plug), but this only works if you won't be moving the tool very far. You'll probably have to make your own extension cords and multi-outlet power cords as well. Be sure that you know what you're doing or have an electrician do it for you. Plugs and wire must be rated for the amperage draw of the tool and everything needs to be grounded.

Tools for home or small shops with motors below 1hp are usually wired for 110VAC. Above 2hp, most tools require 220VAC. In between, tools are either wired one way or the other and some are even offered both ways. If you are on the fence about whether to purchase a 220V or an 110V tool, it's probably time to get an electrician to wire your garage or shop for 220V. You might get away with an 110V tool the first time around, but the next one might require 220V.

Three-Phase Tools

Most homes have only single-phase power, but industrial shops are wired for three-phase. Three-phase motors are smaller, simpler, more reliable, and more efficient than their single-phase counterparts. These are important considerations for a shop with many tools that are used continuously. Tools with larger motors (5-7.5hp) are often only available in three-phase versions and very large motors (7.5hp and above) are rarely single-phase.

Check carefully when you purchase a tool to see whether it uses single or three-phase power. The motor size won't tell you since most industrial shops use three-phase power for all of their tools. If it is a used tool, look at the ratings stamped on the motor. If it reads 3PH (or 3~), it's requires three-phase power.

If you are starting an industrial shop, you'll want three-phase power, but for most home shops the added expense of installing a phase converter is not justified by the benefits. The tools manufactured for use in home shops are single-phase. Only if you have your eye on that 10hp shaper or you purchase a bunch of used 3PH tools, will you need to consider calling the electrician.

Hertz Requirement

Power companies produce electricity in different cycle times throughout the world, generally either 50 or 60 hertz. In the United States the power is generated in the 60 hertz form and tools are sold with 60 hertz motors. If you are living in a country other than the United States you should check which hertz value your local power company produces and determine whether the tool will be able to run on that form of electricity by contacting the tool manufacturer.