The terms get used interchangeably and mostly that is harmless, because what almost everyone sells to homeowners is a pressure washer regardless of the word on the box. But there is a real technical distinction, and it is worth knowing because it tells you something useful about how cleaning actually works.
The distinction
A pressure washer sprays cold water at high pressure. A power washer does the same thing with a heating element, delivering hot water. That is it. Everything else — pumps, nozzles, hoses, guns — is functionally the same.
In practice, hot-water machines are commercial equipment. They are large, expensive, and mostly rented or owned by contractors doing grease, gum, oil and industrial cleaning. Virtually every consumer unit, including every machine on this site, is a cold-water pressure washer, whatever the marketing calls it.
When hot water genuinely helps
Heat dissolves grease and wax. So hot water earns its keep on oily and greasy soiling: a restaurant service area, an engine bay, a garage floor with years of drips, chewing gum on paving. On those surfaces heat does what no amount of cold pressure will.
It also helps on heavy biological growth, because warmth accelerates the chemistry of whatever cleaner you are using. That is a marginal gain rather than a transformation.
When it does not matter at all
Almost every homeowner job. A grimy driveway, a mossy patio, siding with mildew streaks, a wooden deck, a car — none of these need heat. The soiling is dirt and living growth, and the answer is an appropriate detergent with proper dwell time plus a cold rinse. Read the soaps hub for why that works.
Specifically: hot water will not make up for low flow, and it will not remove an oil stain that has soaked into concrete — that needs a pull-out stain remover, hot or cold.
Can you feed hot water into a cold-water machine?
Do not, unless the manual explicitly permits it and states a temperature limit. Pump seals and plastic components on consumer machines are specified for cold supply, and hot water will deform or fail them. This voids warranties and is a common way people destroy a new pump.
What to buy instead
A cold-water machine with good flow, plus the right chemical for the surface. That combination handles everything on a residential property. If you have one genuinely greasy job — a workshop floor, say — rent a hot-water unit for a day rather than buying one.
Shopping advice, as usual, is in how to choose a pressure washer and what PSI you actually need.
