Compare pressure washers on both PSI (pressure) and GPM (flow); PSI × GPM gives cleaning units, a better single number. Electric models around 1,500 to 2,300 PSI suit cars, patio furniture and decks. Gas models around 2,800 to 4,000 PSI handle driveways and large jobs faster. Use the widest nozzle that works: 40 degrees for wood and cars, 25 or 15 for concrete, and never the 0-degree red tip on soft surfaces.
More pressure is not always better. Match the washer to your surfaces, and use the right nozzle at the right distance.
The two numbers
| Spec | Measures | Effect |
|---|---|---|
| PSI | Water pressure | Breaks dirt loose |
| GPM | Water flow | Rinses dirt away, speeds the job |
| Cleaning units | PSI × GPM | Overall cleaning speed |
Look for ratings certified to the Pressure Washer Manufacturers’ Association standard, which makes numbers comparable.
Electric vs gas
| Electric | Gas | |
|---|---|---|
| Typical PSI | 1,500 to 2,300 | 2,800 to 4,000 |
| Typical GPM | 1.2 to 1.8 | 2.3 to 4.0 |
| Noise | Quiet | Loud |
| Maintenance | Minimal | Oil, fuel, winterizing |
| Best for | Cars, furniture, decks, small patios | Driveways, siding, large areas |
Nozzles
| Color | Angle | Use |
|---|---|---|
| Red | 0° | Spot blasting tough stains on hard surfaces only |
| Yellow | 15° | Stripping, concrete |
| Green | 25° | General cleaning, concrete, siding |
| White | 40° | Cars, windows, decks |
| Black | 65° (low pressure) | Applying soap |
Accessories
- Surface cleaner. A spinning disk that cleans flat concrete evenly and fast.
- Extension wand. For second-story siding without ladders.
- Foam cannon. For car washing with soap.
Safety
Never point the spray at people or pets; high-pressure water can cause serious injection injuries. Run gas engines outdoors only, and keep electric units on GFCI-protected outlets.
Indoor jobs? See our cleaning chemistry guide. Browse outdoor and pro.
Common questions
What PSI do I need to wash a car?
About 1,200 to 1,900 PSI with a 40-degree nozzle, held at a safe distance, is enough for most cars.
Electric or gas pressure washer?
Electric is quieter, lighter and suits homeowners. Gas is more powerful and portable for big concrete and siding jobs.
What do the nozzle colors mean?
Red is 0 degrees, yellow 15, green 25, white 40, and black is the low-pressure soap nozzle.
Can a pressure washer damage wood?
Yes. Too much pressure or a narrow nozzle raises the grain and gouges. Use low pressure, a wide nozzle and keep it moving.