Back in the day, we used 12 volt Shurflo Roof Cleaning Pumps with a deep cycle marine battery.
I would clean 2 to 4 roofs a day, and then charge my battery overnight.
I used this kind of set up for years, to clean roofs in Tampa.
They were very slow, but we got the work done, and a good Suntan to boot.
We always used big 5/8 hose, sometimes 3/4.
We have come so far from those days, and have tried to teach roof cleaners a much better way.