If you are talking what they can do, most pressure washer manufacturers have three basic types of pressure washers: light duty, midrange duty and industrial duty machines in electric and gas driven, hot or cold water. If you are talking weight, for example a hot water unit with the same spec as a cold water unit would be heavier as it would have a boiler.

Yes, different tips will give you different spray patterns which can be used for different cleaning applications, as mentioned in the previous email.

There are many accessories available for cleaning, such as wet sandblasters(take paint off of metal), telescopic wands(for high to reach areas), rotary tips(remove rust, graffiti removal, concrete washing, fish nets, grease on concrete floors, grease on heavy equipment, gum from sidewalks, boat/barnacle cleaning, heavy mud/clay removal from heavy equipment.), water brooms( wash sidewalks, driveways, or other flat surfaces).

Cold water is more efficient when used with proper cleaning chemicals. Cold water units have a pump and motor system that can be gas powered or electric. Hot washers make cleaning faster, efficiently loosen grime, grease, gum, etc. Contract cleaners employ mainly hot washers. Hot water units have a pump and motor system( that can be gas powered or electric) and a coil and burner system(usually requires electricity/battery to run the burner and kerosene, diesel oil, furnace oil or propane or natural gas to heat the water)

For cold water units, there are two choices: gas (or diesel-more industrial) engine or electric motor. Gas has fumes. Electric will get the job done with no fumes.

For hot water units, it is a bit different. The pump and motor/engine system has to run as well as the burner/coil system.

Gas powered engine and kerosene, diesel oil, furnace oil or propane or natural gas fired burner with electricity to run the burner/coil assembly

OR

Gas powered engine with 12 volt system and kerosene, diesel oil, furnace oil or propane or natural gas fired burner, no outside electrical source needed (fully self contained)

OR

Electric powered motor with kerosene, diesel oil, furnace oil or propane or natural gas fired burner with electricity to run the burner/coil assembly.

There are fully electric models available, however they are more industrial and require heavier load electrical supplies.

Gas engines have fumes vs. electric motors have no fumes and require a power source. Where there are any fuels being consumed there will most always be fumes. You need to know if you will be operating your pressure washer in an enclosed area or in the open;or if you have the proper electrical outlets if necessary.

Depending on what you would like to accomplish: 1000-2000 psi can clean cars, gutters, fence, decks, boats, etc. : 2000-3000 can clean house siding, pools, and walkways; 3000-5000 can strip paint, heavy grease, etc. As well, the nozzle being used should be taken into account. Red tip nozzle: 0 degree, pencil spray, good for caked on mud/grease on steel, aluminum, masonry, concrete, etc. Yellow tip nozzle: 15 degree, chisel fan pattern, used to remove peeling paint. Green tip nozzle: 25 degrees, wash fan pattern, general cleaning. White tip nozzle: 40 degrees, gentle washing for vehicles and decks. Black tip: chemical application in a low pressure soap system; has a larger hole & wider spray, it siphons chemical and sprays the chemical & water mixture in a wide low pressure spray. And the GPM should be taken into account as well, GPM equals time efficiency. (i.e. 4gpm will do the job faster than a 2gpm)