If he has only just taken the guy on then its unfair to time him yet.
When I take on any new starter I dont expect them to hit full potential till they have been with me a couple of months at least.
Its not all about how long it takes to clean a house. you have to take into consideration many things, such as knowing where the streets are, where each house is, the best place to park to be efficient, will the gate be locked, which pole do I need round the back.
lots of little things make a huge difference over of a day.
We have a company round here offering "free garage door cleans" on every job. If you work out how long it takes to clean a door and multiply that by how many jobs per day, month, year, then your talking hundreds if not thousands of pounds lost. (if your wondering, I recon about 60-70 seconds per door)
If you work on 60 seconds per door,and 15 houses a day over 5 days a week 20 days a month, thats 75 minutes a week or 300 minutes a month, 3600 minutes a year.
So potentialy for a week and a half every year they are working for free.
Like I say.... little things make a difference (if you dont believe me ask my girlfriend)