Cleaning units, not PSI, is the number that tells you how much cleaning power a machine really has. Cleaning units are PSI multiplied by GPM. A 3,500 PSI machine at 4 GPM produces 14,000 cleaning units. The same 3,500 PSI at 8 GPM produces 28,000, which is twice the cleaning power at identical pressure.
Pressure washers fall into two categories based on water temperature, and the choice comes down to what you are trying to remove.
Cold water pressure washers are the most common and the most affordable. They rely on high-pressure water alone, sometimes combined with cleaning chemicals, to remove surface contaminants. Cold water machines are well suited to dirt, mud, sand, loose paint and light mildew on concrete, siding and vehicles.
Hot water pressure washers heat the water before it exits the nozzle, typically reaching 180 to 200 degrees Fahrenheit. Hot water dissolves grease, oil, gum and heavy grime that cold water cannot break down. It is the preferred choice for commercial kitchens, industrial facilities, fleet washing and anything involving petroleum-based contaminants. Hot water machines cost more upfront and need more maintenance, but they cut cleaning time and chemical usage substantially on heavy-duty work.
PSI, or pounds per square inch, measures the force of the water stream. Higher PSI removes stubborn stains and deeply embedded contaminants. It is also how surfaces get damaged: too much pressure on softwood or vinyl siding will destroy them. Residential machines typically run 1,500 to 3,000 PSI. Commercial units reach 4,000 PSI and above.
GPM, or gallons per minute, measures the volume of water the machine delivers. GPM matters as much as PSI because it determines how fast you rinse away what the pressure has loosened. Higher GPM covers more area in less time, which is productivity you can measure on a job. Commercial machines typically deliver 4 to 10 GPM or more.
Cleaning units are PSI multiplied by GPM, and they are the single best measure of a machine's real cleaning power. Two machines can advertise identical pressure and differ by double in how much work they actually do.
| Machine | PSI | GPM | Cleaning Units |
|---|---|---|---|
| Machine A | 3,500 | 4 | 14,000 |
| Machine B | 3,500 | 8 | 28,000 |
Both machines produce the same pressure. Machine B does twice the work. When you compare equipment, compare cleaning units, not PSI alone.
The right machine depends on the work you do, how often you do it, and your budget. This is the general guide our team uses.
| Type of work | PSI range | GPM range | Machine type |
|---|---|---|---|
| Light residential: patios, cars, furniture | 1,500 to 2,200 | 2 to 3 | Electric or small gas unit |
| Heavy residential or light commercial: driveways, siding, decks | 2,500 to 3,500 | 3 to 4 | Mid-range gas-powered unit |
| Professional commercial: buildings, fleets, concrete | 3,000 to 4,000+ | 4 to 10+ | Commercial-grade gas with a belt-driven pump |
Ameritech builds machines across this full range, from the BG3G at 2,200 PSI and 3 GPM for entry-level users, to the BG10BB at 3,000 PSI and 10 GPM for demanding commercial work. If you tell our team what you are cleaning and how often, we will match the machine to the job rather than sell you more pressure than you need.
Cold water pressure washers use high-pressure water alone and are best for dirt, mud, sand, loose paint and light mildew. Hot water pressure washers heat water to 180 to 200 degrees Fahrenheit and dissolve grease, oil and gum that cold water cannot break down, which makes them the standard for commercial kitchens, industrial facilities and fleet washing.
PSI is pounds per square inch and measures the force of the water stream. GPM is gallons per minute and measures water volume, which determines how quickly you rinse away what the pressure loosened. Commercial machines typically run 3,000 to 4,000 PSI and 4 to 10 GPM.
Cleaning units are PSI multiplied by GPM, and they measure total cleaning power. A machine at 3,500 PSI and 4 GPM produces 14,000 cleaning units. A machine at 3,500 PSI and 8 GPM produces 28,000 cleaning units, which is twice the cleaning power at the same pressure. Always compare cleaning units rather than PSI alone.
Professional commercial work on buildings, fleets and concrete generally calls for 3,000 to 4,000 PSI or more at 4 to 10 GPM, using a commercial-grade gas machine with a belt-driven pump. Light residential work needs only 1,500 to 2,200 PSI at 2 to 3 GPM.
Yes. Excessive pressure on delicate surfaces such as softwood or vinyl siding will cause damage. Matching pressure to the surface matters more than buying the highest PSI available, which is why cleaning units and nozzle selection matter more than peak pressure.
Tell our Tampa team what you are cleaning and how often. We will match the machine to the job.
Talk to the Tampa Team