How many decibels is a pressure washer?
Sun Joe says 89 or 96 dB(A) of sound power. Greenworks says 68 dB, and the two are not the same kind of number.
Sun Joe prints "Sound power level is 89 dB(A)" or "96 dB(A)" in its manuals, as the explanation of a decal on the machine. Sound power describes total emission, and is always a higher number than the sound pressure most people picture.
Greenworks says "Very quiet at only 68 dB" and lists "Low Noise 68 dB" in its specification block. Sound power or sound pressure? It never says, gives no distance and names no standard, and its manuals carry no acoustic declaration at all.
A straight ranking would put Greenworks 28 decibels ahead of Sun Joe, and that would be meaningless. Greenworks' unlabelled 68 dB set against Sun Joe's 96 dB(A) of sound power is exactly the pairing our page on comparing decibel ratings warns against, so the two brands are kept apart and ranked within what each publishes.
One comparison does hold.
Within Sun Joe's range, on its own measurement, the SPX3000-MAX publishes 89 dB(A) while ten other models publish 96 dB(A). That 7 dB gap is like for like.
How loud is a gas pressure washer?
Nobody will say. Karcher's US gas range comparison table has no acoustic row, and neither do Champion, Simpson, Westinghouse or Generac. We looked for gas models to use as loud reference points and could not source a single figure.
A gas engine is obviously louder than an electric motor, but with no published number we will not invent one, and neither should the retailer listings that quote figures the manufacturer never published. A "68 dBA at 23 ft" claim, for example, circulates for one gas machine and appears nowhere on that maker's site.
Engine noise is better documented for generators, and our generator guide collects those figures, though its makers quote them at different loads and distances.
Nobody backs the induction motor claim in writing
Online advice says induction motors run quieter than universal ones. We went looking for a pressure washer maker who says so, and found none, nor any that ties motor type to a noise figure.
Sun Joe's manuals give only an amp rating, 13 amp or 14.9 amp, and never use either word. Greenworks says "Motor Type Brushless". The claim cannot be repeated as fact.
Buy electric, and battery if you can
Both published figures in this guide belong to electric machines, and the gas makers publish nothing. Greenworks' battery models carry the lowest published figure, and you lose the cord as well. Expect to wear hearing protection anyway. Sun Joe's manuals include a decal explaining the sound power level, which is there precisely because these are loud machines.
Eco mode is no shortcut. On the Greenworks models it drops maximum pressure from 3000 PSI to 2200 PSI and reduces flow, with no separate noise figure, so any noise benefit is unstated.
Five claims that trip buyers up
The first is 68 dB set against 96 dB(A): different quantities, from different brands. The second is a quietest badge, when only three brands publish a figure at all and most of the market is unranked; our guide to the quietest electric pressure washers covers the Karcher figures. Third comes the induction motor story, which nobody in this category puts in writing.
Peak PSI is the fourth. Sun Joe distinguishes pressure at initial discharge from rated pressure under load, and the second number is the useful one.
Last is the idea that eco mode is quieter. It lowers pressure, but its noise goes unpublished.
