Small consumer gas pressure washers are particularly great for two reasons: They have more cleaning power than electric units, and they can be used away from an electrical source.
With PSI ranges from 2200-2700, you can clean a wider variety of things than you can with a consumer electric pressure washer, and you can clean them faster.
Capabilities of a Small Consumer Gas Pressure Washer
As far as cleaning projects you can undertake, a small gas pressure washer can handle most tasks, short of stripping paint. Some stains may be too resilient for cold water alone - you might need detergent or a hot water unit for the most serious stains.
High Pressure Warning
When cleaning things like siding or a boat, make sure to start a good distance away and get in closer as needed. The pressure can be strong enough to damage these things.