Pressure washers: professional cleaning at a do-it-yourself price has helped move pressure washers beyond the tool-rental shop and into your local home center.(Home and Yard)(Market overview)

Pressure washers use a gas engine or electric motor, pump, and concentrating nozzle to boost water, pressure from your garden hose as much as 60 times. That lets them blast away deck mildew, driveway stains, and other grunge a hose can't touch while cleaning chairs, siding, and other items more quickly and easily than you could with a scrub brush.

For as little as $90 for electric machines and $300 for gas, owning one is a tempting alternative to renting one for $50 to $90 per day.

Lower prices and less upkeep explain why 60 percent of buyers choose an electric pressure washer. But gas machines have roughly twice the cleaning power, which is the main reason …