A corded pressure washer is one of the highest continuous electrical loads most households will plug into an outdoor receptacle, and it is being operated by someone standing in water. That combination is why the electrical section of a pressure washer manual is unusually strict, and why the restriction people most often ignore, the ban on extension cords, is there for a mechanical reason rather than a legal one.
What these machines actually draw
Corded machines in this catalog cluster in a narrow band near the top of what a standard household branch circuit provides. The Greenworks GPW2003 is listed with a 14 amp motor. The Sun Joe SPX3001 publishes the full picture: a 14.5 amp, 1,800 watt motor at 120 volts. The Sun Joe SPX4800 and the Sun Joe SPX3000-XT1 are both listed at 14.9 amps. The Worx WG605 sits slightly lower at 13 amps.
A standard residential branch circuit in the United States is protected at 15 amps, and the accepted design practice is to load a circuit to no more than 80 percent of its rating for a continuous draw, which works out to 12 amps. A 14.9 amp pressure washer exceeds that continuous figure. In practice these machines cycle rather than run flat out, and most manufacturers specify a dedicated 15 amp circuit for exactly this reason. Sharing that circuit with a refrigerator, a freezer, or shop lighting is how nuisance trips start.
The GFCI is part of the machine, not an accessory
Nearly every corded unit in the electric listings ships with a ground fault circuit interrupter built into the plug or into a module a short distance down the cord. The Greenworks Pro GPW3001 is listed with a 35 foot GFCI power cord, and the Greenworks GPW2300 with a 35 foot cord carrying an inline GFCI described as intended for exterior outlets. The Westinghouse WPX3000e uses the same 35 foot GFCI arrangement.
A GFCI compares current flowing out with current returning and cuts power in milliseconds when the two do not match, which is what happens when current finds a path through a person. It should be tested with its own test and reset buttons before each session. A GFCI that will not trip on test, or will not reset after tripping, takes the machine out of service until it is repaired. It should never be bypassed, taped down, or replaced with a plain plug.
An outdoor receptacle in a modern installation is itself GFCI protected. Two devices in series is not a problem and is not redundancy worth removing.
Why manufacturers restrict extension cords
The reason is voltage drop. Every foot of cord has resistance, and current through resistance loses voltage. A motor supplied at reduced voltage does not simply run slower. It draws more current to produce the same mechanical output, which raises the heat in the windings, which raises the resistance further. Prolonged operation in that state cooks the motor, and the failure is usually not covered by warranty.
Undersized cords make it worse in the direction people least expect. A thin cord on a 14.9 amp load can get hot along its whole length, and a cord coiled on a reel while carrying that load cannot shed the heat.
The manufacturers’ answer is to make the supplied cord long enough that no extension is needed. Thirty five feet is the common length across this catalog, and it is chosen so that the machine can be positioned near the outlet while the water hose and the high pressure hose reach the work. Not every unit follows the pattern: the Le Hao Tool listing gives a 16.5 foot power cord with inline GFCI, which is less than half the reach of the mainstream units and increases the temptation to add a cord.
Where a cord is permitted
Some manuals allow an extension cord and then specify the terms: a minimum conductor gauge, a maximum length, an outdoor rating, and a three prong grounded configuration. Where those terms are published, they are the terms. Where a manual prohibits extension cords outright, that is the instruction that governs, and no gauge of cord makes it acceptable.
Indoor rated cords have no place outdoors regardless. Neither does any cord with a damaged jacket, a missing ground pin, or a connection lying in water.
A note on wall mounted units
Wall mounted machines change the electrical question because they are installed rather than carried. The Giraffe Tools Grandfalls PRO is listed with an 1,800 watt brushless motor and a 100 foot retractable hose, an arrangement that puts a permanent load on whatever circuit serves the garage or exterior wall. The hose length is what supplies the reach, rather than the cord, which sidesteps the extension cord problem entirely. What it introduces instead is a fixed installation exposed to weather, which is a question for the receptacle and its cover rather than for the machine.
Total stop systems and what they do to the load
Most corded machines now shut the pump off when the trigger is released rather than running continuously against a bypass. Listings describe it as a total stop system or as start and stop technology, and the Greenworks GPW2003 listing notes that the motor switches off when the wand is not engaged to save energy and extend pump and motor life.
The electrical consequence is that the motor restarts every time the trigger is squeezed, and a motor draws a brief inrush current well above its running figure at each start. On a circuit already close to its limit, that inrush is what trips the breaker, which is why a machine can run for twenty minutes and then trip when someone else switches on a load elsewhere in the house.
Water and electricity in the same working area
The jet must never be aimed at an outlet, a light fixture, an electrical meter, a service panel, an outdoor disconnect, or the pressure washer’s own cord and plug. Water forced into an energized enclosure at working pressure is an entirely different hazard from rain landing on it.
Connections should be kept off the ground and out of standing water. Plugging and unplugging with wet hands is worth avoiding even with a functioning GFCI, because the device protects against a ground fault and not against every contact scenario.
The one machine type with no electrical requirement
Engine driven units in the gas listings have no cord, no amperage figure and no GFCI, which removes this entire category of hazard and replaces it with a worse one. A gas engine emits carbon monoxide, which is colorless and odorless, and a gas pressure washer must never be run indoors or in a garage, including with the door open. Trading a cord for an engine is not a safety upgrade.
The document that governs
Circuit requirements, cord rules and GFCI instructions vary between models, and the manual supplied with the specific machine takes precedence over anything general. Where a listing does not publish an amperage figure, and several in this catalog do not, that figure should be confirmed from the manual before the machine is plugged into a shared circuit. As with any pressure washer, the jet must never be aimed at a person or an animal, and any suspected injection injury is a medical emergency.
