Tom Bosley -- who famously played Mr. Cunningham on  Happy Days  -- died this morning at a hospital in Rancho Mirage, CA ...
Average estimates: $250 to $420. Power washers can have pressures of 4,000 psi (pounds per square inch) to lesser pressures of maybe a few hundred and run by gas or electric. This means that professionals will probably use one with less pressure to clean a deck and maybe one with higher pressure to clean a patio.
1 Power Washing, Stain and Seal : $1.00-$2.00 per square foot depending on surface condition, intended outcome (mold/mildew issues), and access. 2  Power washing a deck is good for cleaning the surface but Never use the aggressive pressure of the water as the cleaning factor.