I had a 9kw webasto 2 man 650 litre system from purefreedom for 4 years, I currently have a 3kw immersion heater in a 500 litre tank, 9 months of the year I use cold water. 95% of my work is 4 weekly regular maintenance cleans, I use a backpack to do my work as I just couldn’t get on with hose reels. Whether I use very hot, hot, lukewarm or cold water I clean the same amount of houses per day in the same time. The main reasons for this is that for some strange reason hot water doesn’t push the brush up and down a window any faster than cold water does, it doesn’t make me walk any faster, it doesn’t make getting the equipment out of the van any quicker etc, etc. I don’t hang around long enough to time how long the windows take to dry and I don’t need to go inside a property to make sure I have cleaned the windows properly, I’m sure the customer would let me know if they weren’t.
I clean my own windows and whether they are cleaned with hot or cold water the result is the same......clean windows.