Workshop Power: What a Home Shop Actually Needs

Read the nameplate: amps are the number that matters

Every power tool has a plate or a label stating its voltage and its current draw in amps. That amp figure is what your circuit has to supply. In a typical North American home shop, a general-purpose outlet circuit is 15 or 20 amps at about 120 volts, and it is shared — the garage outlets, the lights and sometimes a bedroom may all be on the same breaker.

Two things follow. First, a 15-amp tool on a 15-amp circuit is right at the limit, and it will trip the moment anything else on that circuit draws current or the tool bogs down in a heavy cut. Second, motors draw a large surge at startup — far more than their running figure — which is why a saw can run fine all day and still trip the breaker every time you switch it on with the shop vac already going.

The practical version: check the amp rating of the machines you own, and know which of your outlets share a breaker. A dedicated circuit for the biggest machine solves more problems than any accessory you can buy.

Horsepower claims and what they mean

Motor horsepower is quoted inconsistently across the tool market, and "peak" or "developed" horsepower figures on consumer machines are marketing numbers rather than continuous ratings. The honest way to compare two machines' real appetite for power is the amp draw and the voltage on the nameplate, because that is the electrical reality your shop has to supply. When we describe a machine as power-hungry in a roundup, that is the figure we are reading.

When 240V is worth it

In North America, larger stationary machines are often available in a 240-volt version, and many mid-size ones can be wired for either. The advantage is not magic extra power — the same motor doing the same work needs the same wattage — but at double the voltage it draws roughly half the current. Lower current means less voltage drop in the wiring, less heat, and a motor that starts and recovers under load more comfortably.

For most home shops running benchtop and portable machines — a compact planer, a jobsite table saw, a sander— 120V is entirely adequate and 240V is not worth the wiring. It starts to earn its keep when you move to cabinet-class machines, a larger bandsaw, or a bigger dust collector, especially in a detached garage or shop where the run from the panel is long. If you are planning a shop from scratch and the walls are open, running one 240V circuit while it is cheap to do is a decision people rarely regret.

Extension cords: the quiet power thief

A long, thin extension cord drops voltage along its length, and a motor fed low voltage draws more current to do the same work, runs hotter and starts poorly. This is the single most common self-inflicted power problem in a home shop, and it is completely avoidable.

Two rules cover it. Use a cord with a heavier gauge than you think you need — lower gauge numbers mean thicker conductors, so a 12-gauge cord is substantially better than a 16-gauge one for a machine. And use the shortest cord that reaches; coiled surplus cord makes the drop worse and traps heat. Cord packaging normally states the maximum length recommended for a given amp draw, which is the figure to follow.

A better answer than any cord is more outlets. If you are fitting out a shop, outlets every few feet along the wall at bench height is the upgrade that quietly improves everything — including how tidy and safe the floor stays. Our garage workshop layout guide covers where they want to be.

Lighting is on the same budget

Shop lighting draws very little current by modern standards — a run of LED fixtures adds up to a fraction of one machine — but it is usually on the same circuit as the outlets in a garage, which is why the lights dim when a big saw starts. If your lights sag noticeably at startup, that is a useful signal about the state of that circuit. Our shop lighting roundup covers the fixtures worth buying and how many you need for the area.

Where to stop and call an electrician

Plugging a tool into an existing outlet, buying a proper cord and rearranging what runs at the same time are all things anyone can do. Adding a circuit, changing a breaker, converting a machine to 240V, or wiring a subpanel to a detached shop are not; they are regulated work in most jurisdictions for good reasons, and doing them badly is a fire risk and can invalidate your insurance.

If you go that route, the useful preparation is a list: every machine you own or plan to buy, each one's voltage and amp draw from its nameplate, and which ones will ever run at the same time — a collector runs alongside whatever machine it is serving, which is exactly the pair that trips a shared circuit. An electrician can size the work from that list in minutes.

What we could not verify

We have not measured voltage drop or current draw in any shop, and we are deliberately not quoting wire gauges or breaker sizes for your installation, because the correct answer depends on your local code, your run lengths and your panel. Everything above is the general behavior of motors and cords, plus what a tool's own nameplate tells you. Treat the nameplate as the source of truth and a licensed electrician as the authority on the wiring.