I use around 150 to 175 litres per day.
By myself I'll do around 20 houses per day, doing 1st floor only. I do traditional on the ground floor; mostly. Leaded or Georgian I do the lot WFP.
I'm only 'small cheese', but enjoying myself.
What's your flow rate per minute?
From my limited experience and from what I've read here, anything from 1 to 2 litres per minute is fine. More is better if you can 'afford' it.
I like around 1.5 litres per minute.
You can measure it simply by getting a bucket and pump water in it for one minute through your brush head. Then pour the result into a measuring jug.
My back pack pumps out on setting two around 1.5 to 2.00 litres per minute. My 60 psi shurflo jets out around 5 litres per minute, but I hardly use this.
I haven't read any posts about 'litres per hour', only 'litres per minute', so I can't really comment.
How many litres per day are you using and what's your type of round?