Get the machines made to spec by your pressure washer guy, save yourself the mither, also get a warranty if anything breaks which in total from making it to using it to fixing it means less downtime for you where you could be working and earning or promoting... for the sake of saving a couple of hundred quid it's not worth it in the long run...
yep spot on mate, currently we use 18 ltr washers during yr looking to get larger diesel static via local guy custom built, same as our recent hotbox.
I do understand where Chris is coming from with portable setup, our main investments are in the vans as without a reliable van best washer in the world is useless. We offer other services hence at present can't tie up vans for some of the cleans.
Most of our cleans are roofs we use petrol 15 hp 18ltr usually runs at half revs, at most £15. Only notice petrol cost when we do large com's.
My set up is totally portable yet also fixed in the van, so i can wheel it out if I need to, I have a brendon diesel yanmar trolley machine with a cat45 pump, stapped to the van on the side door, I have took away the throttle governer so when i'm whirlaway-ing i can push it up a bit more to get 17 lpm at nearly 250 bar on 2 x 025 nozzles, then when the turbo goes on i knock it back a little and do 3000psi @ 15lpm,
i have adapted it and put a 30 m hose reel on instead of the 15 metre (30 meter is usually enough for me) but when I am a greater distance away I have another 20 metre extension if i need it so in total 50 metres of hose.... if for whatever reason I need to take the machine off the van (very rarely needed to with 50 m of hose reel) then I just undo the ratchet strap that holds in down next to the side door and wheel it of using my wheelchair ramps....
In 99% of jobs though I just whip open the side door, pull the hose to where im work, attatch my kew spiggot gun and press the electric start, hey presto, up and running within 3 mins without having to return to the machine again unless I need to refuel.... works for me, i also have the bonus of it still being on wheel so can take it off if ever I need to... my diesel runs about 5 - 6 hours on a full tank ( 6 litre I think) uses about 1.1 litre per hour at 90p per litre