These units are great where you may not have access to an electrical outlet or if your electricity is not reliable. Some units have batteries, some don't and the burners typically come in 12 volt or 120 volt units.

Many manufacturers claim that the 120 volt burners are better and more reliable than their 12 volt counterparts. Some use generators that generate 120 volts to power the burners so that they can use a regular 120 VAC oil burner. If you are going to frequently start and stop your pressure washer, then look for a unit that does not have a battery for ignition. Frequent starts and stops can eventually wear the battery down so keep this in mind when selecting a unit.

There are two basic mounting styles that gas powered pressure washers come in. The first style is the portable style on wheels. This style has everything you need including a water tank. You can just roll the unit right up to the job and start working. It is very convenient for jobs where you can't just drive a truck up to where you need the washer. The water tank, pump and other components are mounted on a powder coated frame and ride on little tires so you can easily roll the unit around. These are intended for outdoor use only.

Skid mounted pressure washers are mounted to either a truck or a skid. The water tank is mounted alongside the unit. Skid mounted gas powered pressure washers have larger tanks and can do larger jobs than their wheeled counterparts. The downside is that you must have room to bring the truck or skid to the place where you need the pressure washer. In industrial environments this is usually not an issue.

These pressure washers are often mounted on a trailer so that they can be wheeled to the job and left there until they are needed elsewhere.

They are powered by gasoline and the water is heated by diesel in their most common configuration.