I have a 9 kw wabasto system fitted by Grippatank it’s awsome but not cheap to run , we have 2 hose reels going all day if water isn’t going on the glass it’s returning to the tank by lunch time the tank is quite warm and we have a 1000 ltr system it’s not cheap to run though I put about £70 a week In Fuel in the vehicle tank cannot work out the mpg or how much the wabasto uses as it’s the same tank but at a guess I think it’s got to be 1 ltr per hour or maybe slightly more most of my work is close to home apart from the stuff we do In Bristol . Personally I would t go back to cold hot is quicker , better results don’t ask me why but it is used cold for 10 years then put a boiler in and finish is better better shine on the glass , we do loads of plastic cleans , industrial building wash downs , cladding, solar panels , time saving is very good on the very dirty stuff , we use it all year round and it’s running 8 hours a day minimum