said by nunya:It's because of the split service. Have you seen the price of the $400A transfer switch?
It probably would have been better to have two panels: essential circuits and non-essential circuits. Especially since they are right next to each other. Then he would have only needed one ATS.
The concrete pad and propane feed from the tank can support up to a 30-35 KW unit. If in the future, 20 KW is insufficient, swapping out a 20 for a 30 or 35 is a heck of a lot easier than rewiring, pouring new concrete and running new propane lines.