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Most corded shop vacs draw 7 to 12 amps at 120 volts, which is roughly 840 to 1,440 watts. Small 2 to 6 gallon units typically sit at 5 to 8.5 amps; the common 12 to 16 gallon household models run 9 to 12 amps. A standard 15 amp US branch circuit has a continuous working limit of 12 amps under the National Electrical Code 80 percent rule, so a 12 amp vacuum uses essentially the whole circuit and cannot share it with a saw. The exact figure is on the data plate, not the peak horsepower sticker.
What do typical models draw?
Amp draw tracks motor size rather than drum gallons — several manufacturers use the same motor across their 12 and 16 gallon bodies. These are the bands that cover almost every consumer wet/dry vacuum sold in the US.
| Size | Typical amps | Approx. watts | Circuit headroom |
|---|---|---|---|
| 2–4 gal compact | 4–6 A | 480–720 W | Plenty on a 15 A circuit |
| 5–8 gal | 6–8.5 A | 720–1,020 W | Room for lights and a charger |
| 10–12 gal | 9–11 A | 1,080–1,320 W | Near the 12 A continuous limit |
| 14–16 gal | 10–12 A | 1,200–1,440 W | Effectively the whole circuit |
| Cordless 18V/20V | 0 A household | — | Charger only, ~2 A |
Will it share a 15 amp circuit with a saw?
Usually not, and this is the question that actually matters in a workshop. The NEC limits a circuit to 80 percent of its rating for continuous loads, giving 12 amps usable on a 15 amp breaker and 16 amps on a 20 amp breaker. A 15 amp table saw or a 15 amp miter saw already exceeds the continuous limit on its own, so adding even a 7 amp vacuum guarantees a trip the moment both are cutting. The practical solutions owners settle on are a second circuit, a 20 amp receptacle for the saw with the vacuum elsewhere, or an automatic tool-actuated outlet that only powers the vacuum during a cut. Our page on running a table saw on a 15 amp circuit works through the same math from the saw side, and how many amps a circular saw draws covers hand-held tools.
What extension cord does a shop vac need?
Gauge matters more than most people assume, because an undersized cord causes voltage drop, which makes the motor draw more current and run hotter. For a 10 to 12 amp vacuum, use 14 AWG up to 50 feet and 12 AWG beyond that. For a small 6 amp unit, 16 AWG is acceptable to 25 feet. Use a cord marked for outdoor use where relevant, keep it fully uncoiled — a coiled cord under load builds heat — and plug into a GFCI-protected receptacle, which the NEC requires for garage, basement, outdoor and similar locations. GFCI protection is not optional if you intend to vacuum water; see can a shop vac pick up water.
What does it cost to run?
Very little, because run times are short. At the US residential average of roughly 17 cents per kilowatt-hour reported by the Energy Information Administration, a 12 amp vacuum consuming about 1.44 kW costs around 24 cents an hour. A 20 minute garage cleanup is under a dime. Even a full day of jobsite use is a rounding error compared with the tools it supports. Efficiency is not a reason to choose one shop vac over another; airflow, filtration and hose diameter are.
Where to go next
For choosing a machine, our ranked best shop vacs compares current models on aggregated owner ratings and recurring complaints, and what size shop vac do I need covers sizing by job. Filter problems are in why a shop vac blows dust out the back. Everything sits under the power tools and workshop hub.
Electrical work beyond plugging in a tool is jurisdiction-specific — local amendments to the NEC vary and permits may be required. Use a licensed electrician for new circuits. We never buy or physically handle the tools we rank; our method is on how we rank.