The electric washers are usually rated about 1800 psi, about 1000 less than gas driven and are cheaply made. The problem I had with a couple models were the seals in the hose and sections of the gun. I couldn't buy just the seals, but the whole gun. Odd size seals and o-rings that I couldn't match up.
If you have a water maker, the high pressure pump may be capable of sending enough water for pressure washing. If you're handy, there isn't much difference in the pumps.
There's a number of 12 volt compressors & tanks on ebay. Made for air horns. If you have a bigger diesel with accessory positions on the gear drive, there's probably a matching compressor available. Often used ones on ebay.