Pressure washing and its big brother, power washing (aka hot pressure washing), can make a home look new in just a few hours. It's necessary before painting a home, re-staining a deck, or even refinishing a pool.

In addition to being much faster than hand-scrubbing surfaces, pressure washing offers a deeper clean, particularly when it comes to nooks and crannies.

Units start as small as 100 PSI to 750 PSI. These are normally battery-powered models that are designed for quick, portable spot cleaning or other small, light jobs that don't require getting out the bigger machine. Some even have the option to draw water from a five-gallon bucket instead of dragging a long length of hose around. They excel at cleaning windows, spot cleaning lightly soiled patio furniture, including cushions, and rinsing off cars, RVs, motorcycles, bicycles, and scooters. At this size, they are normally available only for purchase rather than renting.

Remember that even with a low-PSI model, pressure washers are dangerous -- never aim them at another person, even when just horsing around.

For all other jobs, a 1,000 PSI to 1,900 PSI light-duty washer is normally the bare minimum. Although there will be an overlap with the smaller guys when it comes to washing vehicles and cleaning outdoor furniture, the increased pressure makes the work quicker and it can remove tougher and more-ground-in stains. Designed for the light-use homeowner, they also make short work of cleaning small patios and decks and outdoor play equipment, whether plastic, metal, or wood.

One step up, heavy-duty pressure washers (2,900 PSI to 3,300 PSI) will quickly remove built-up dirt and grime from siding or stucco exterior walls, strip coatings and sealers from concrete and brick, and brighten up a dingy sidewalk. They're the right choice for large driveways or even parking lots.

Many commercial pressure-cleaning businesses use this size machine, while truly professional-grade machines are considered to be 3,400 PSI and above. Those are used for restoring severely built-up dirt, grime, etc., on concrete and brick, cleaning multi-story buildings in preparation for paint or sealing, and removing graffiti.

While there is a temptation to think that bigger is better, selecting too high a PSI can damage the surface being cleaned, particularly wood surfaces such as siding and decks.

Also check out the machine's gallons per minute (GPM) rate. A higher GPM will get the job done faster. Common GPMs are 1.5 GM to 2.5 GM for light jobs, such as washing the car, and 2.4 GPM to 4 GPM for cleaning sidewalks and siding.