Apart from cost, why don't more people use it then?
I expect a lot of window cleaners have not been able to make any comparisons between the hot & cold versions.
The Birmingham cleaning show would be a good opportunity for the likes of Ionics to set up 2 window cleaning demonstrations side by side (one a hot wash & the other a cold wash) to show off/sell the Unique Selling Points of their hot wash for us window cleaners to consider spending the extra money required for these hot wash systems.
Until you've tried a hot wash system day in and day out you can't really knock it apart from initial cost and running cost but I can justify the extra cost because of the extra work I am doing in a day as a result of using hot water!