Hot water vs cold water pressure washer
Updated 2026-09-04
- Best overall
- Cold water, for residential exterior cleaningNearly everything on a house is biological, and chemistry beats heat on biology.
- Best for grease
- Hot water, decisivelyKitchen exhaust, dumpster pads, fleet and workshop floors — heat is the difference between one pass and four.
- Best budget
- Cold water, and it is not closeA hot-water unit costs several times as much, weighs more, burns fuel and adds a burner to maintain.
The difference in one table
| Spec | Hot water | Cold water |
|---|---|---|
| What it adds | Heat, typically to around 200 deg F | Nothing — pressure and flow only |
| Beats cold on | Grease, oil, fats, waxes, gum | Nothing, but matches it on most residential work |
| Weight and size | Burner, coil, fuel tank; often skid or trailer | Cart or skid, moves easily |
| Extra consumables | Diesel or kerosene for the burner | None |
| Extra maintenance | Coil, burner, fuel filter, descaling | Pump and engine only |
| Purchase cost | Several times a comparable cold unit | Entry point for the trade |
| Risk of surface damage | Higher — heat softens coatings and sealants | Lower |
Cold water carries the pick because it is the right first machine for almost everybody. That is a statement about which jobs most operators sell, not about capability.
What heat actually does
Heat lowers the viscosity of oils, fats and waxes and helps the surfactant get underneath them and lift them off. On a grease-soaked dumpster pad or a restaurant’s back apron, that turns a four-pass cold-water job into one hot pass, and it does it without raising the pressure.
It also shortens dwell times on some degreasers and helps with chewing gum, tar and similar sticky contamination that cold water treats as furniture.
What it does not do: heat is nearly irrelevant to algae, mildew and lichen, which is what covers most residential exteriors. That work is a chemistry problem, and hypochlorite at the right dilution does it whether the water is hot or not.
What it costs to own
A hot-water machine is a cold-water machine plus a burner, a coil, a fuel tank and a set of controls, and every one of those is another thing to service and another thing to fail on a Tuesday morning.
- Fuel. The burner runs on diesel or kerosene and consumes it steadily whenever heat is on.
- Descaling. Hard water scales the coil. Neglect it and the coil is a large bill.
- Weight. Most units are skid or trailer mounted, which changes the vehicle you need.
- Winter. More water sits in more places, and all of it can freeze.
Surface damage risk
Where it pays for itself
Three markets justify the purchase, and they have a common shape: recurring commercial contracts where the contamination is petroleum or food fat.
- Restaurant and retail back-of-house. Dumpster pads, drive-throughs, grease-tracked aprons — usually scheduled monthly.
- Fleet and equipment washing. Road film, oil and diesel residue on vehicles and plant.
- Industrial and workshop floors. Where cold water and a degreaser simply take too long to be economic.
The test is straightforward: if you have signed recurring grease work, the machine pays for itself in labour hours. If you are cleaning driveways and houses, buy a better cold machine, a bigger surface cleaner and more chemical instead.
The middle path