What is the recommended residential hot water setting?

Generally somewhere between 'hot and very hot'. If you have small children, then leave the setting on hot. Water over 120 degrees can scald a child in 3 seconds, be careful.

105-115 degrees.

Hotter than 120 is a safety risk- and burns up cash as well.

I did an interesting experiment with my family (please don't tell). I turned down the hot water setting a couple of degrees each month for 6 months. Went from 118 to just over 100.

The dishes, kids and clothes are still clean, and the gas bill is smaller with no one complaining too much- including an 11 year old girl (!).

My wife did the same thing to me to go from whole milk to skim, so i figured turn about was fair play.

Good advice from Robert K except I would add that I wouldn't go over 120 for safety reasons even without kids. It is more efficient if you don't need the extra hot water to lower the temperature.

If there was such a thing as one setting that was best for everyone, then the thermostat would be fixed at that temperature and made so you can't change it. Depending on the people living there and what their specific needs are, there is no setting right for everyone. Yes, keep it lower if you have kids or elderly people. Keep it higher if you are younger and like to take long showers. This list goes on and on and on..

Not over 120 degrees.

However, a dishwasher works better at 140.

Not over 120 degrees.

you can set it any where you want but the installer has to set it no higher than 120 degrees.

The common setting should be about 120o