For showers: set to 109 degrees, Use hot only
For kitchen/bath single handle faucet: 125 degrees
Remember, when you turn off water at faucet, even for a moment...the hot water system turns off. Then when you turn water at faucet on again, it takes time for new water entering the hot water system to heat up and travel all the way to the faucet. Granted, there is still hot/warmth within the line, but once that runs thru, you get cold for a moment until the “new hot” water travels to you.
And if you place your single handle faucet “in the middle”, the hot water system will ignite and use propane but it may take a gallon or more before you feel warmth.
So, its best to either run “all hot” or “no hot” if your goal is to use as little propane as possible.
'17 Vegas 24.1