I think it'd be hard to get a solid set of data for this, as fridge contents are going to be a major factor to how quickly it gets cold, what their starting temperatures are etc.
I can add the following anecdotal information:
shortly after getting my van back from SalemKroger, my beer fridge was empty. I loaded it up with beers, cokes, waters, and vitamin waters before leaving in the morning for golf. When we were getting out of the van, my buddy cranked the dial all the way to 5 without my knowing (because I had already learned this lesson). When we came back to the van 7 hours later, we had mostly frozen beverages. The cans and bottles were probably 60 degrees when we put them in in the morning at 6 am.
My fridges are both left running all the time, so I don't get a lot of experience with them 'coming down to temperature'.