Ive been using hot, diy system, for over 3 yrs.
I use it all year round on every job & find it helps with cleaning bird muck, bee spots etc.
I prefer it in the summer when the heat can be turned up to aid cleaning , where as in the winter, you have to turn it down to luke warm, so you dont break the glas, but its just nicer to use.
Its also better for con' roof & gutter/ fascia cleaning, i dont pre treat these jobs anymore.
Knowing all this, would i spend 3-4-5 thousand on a pro system,
I dont think so, personally.
But cheap diy, excellent value for money