Dual vs Single AC units.

unless it is a long term park and your electric usage is billed extra... RUN IT ALL !!! 50 amp service and stay cool

Common?
You need to check to see what ducted outlets come off which AC unit. Yes, the bedroom one should only feed the bedroom, however it is possible that the duct from the bedroom unit may feed into hall or bath area.
Some thermostats or system allows the AC unit to switch automatically from AC units. This would allow the whole rig to stay cool, yet save energy by running only one at a time.

I have two and when I go home I have a meter hookup since I stay for several months. The total for two months average out is less than $10 per month for both running. That is going to be different depending on where you are at and cost of utilities.

If the coach in question will only support 30A service and is older, then it will be able to only run 1 at a time. If its newer and has some kind of a power management module, then it will likely be able to run both (switching). If it is ducted, then you could run 1 and force some of the air to the back (assuming that it is ducted that way). But, in a hot enviroment, I suspect that you'll be unhappy with the results (both front and back).

We had an older 30A coach prior to what we have now and it could run only 1 AC unit when hooked to shore power (both were powered when it was running via the generator).

We would shut the door to the bathroom during the day (which was right in front of the bedroom) and it would keep the front half cool. At night, I would switch AC units. That arrangement pretty much did not work for me as it generally took an hour or so to completely cool things and it never really kept the coach as cool as I would prefer. And, during the day the bathroom was always hot.

So, I actually made a change to the RV and wired up a means to allow me to run the rear AC unit on a separate 20A circuit. Once I did that, it worked well. The campgrounds we went to had both a 30A and a 20A circuit (separate) that allowed this to work. Once I had that, I was happy as a clam with the temperature in the RV (my wife even complained that it got too cold).

On a coach that supports 50A service, you can run both of them all the time.

Regardless of what the coach has currently and if you go anywhere south in the summertime, you will want and need to run both units. We did not enjoy our trips as much when we had just 1 AC unit available.

Our M/H is 31' and has a single ducted A/C unit. It was replaced last year with a larger unit on the roof. I can't remember the BTU's sorry.

I live in Georgia so you can imagine how muggy and hot it is here in the summer. That one A/C unit cools the entire coach to 72 Degrees without any problem. The Bedroom stays just as cool as the front area. There are 2 ceiling ducts in the BR and I think there are 8 in the rest of the coach. My only complaint is the bathroom (closet)isn't ducted. My DW just keeps the door open a few inches and it keeps it cool enough to tolerate.

We wanted a m/h without slides. That may be the reason why our 1 A/C unit works for us. We aren't cooling the extra space. With all the slides they offer I can see the need for 2 units.

in our Monaco, the ducts in the ceiling are continuous.
We often run only the front A/C during the night to keep it quieter in the bedroom, plenty of cool air comes through the ducts.

I'd guess if you need to save money on power, turn the temp up a bit. Costs way less to hold 80 than 75, right?
Not sure trying to isolate the bedroom is the best choice, and then what happens when you go to use it and it's 90 in there?
It requires a lot less a/c to maintain a temp than to achieve it, especially if the nights are cool and you can leave the units off at night.

All depends on amps. If it is 50a, it will run both. 30a, and one.

on my RVs with 2 ACS I could run either one of them separately. could run both using EMS. that was one thing great about two units, could usually run the one in the area that we were not in, front one at night, etc.
bumpy

We have a 2002 32 foot Itasca Sunrise with two units and the power management system, we can run both on shore power and on generator, however since we only have a 30A system, if we use the microwave or a hair dryer, we have to shut one of the AC units off.

You can't just assume running two units will cost more than running one. The opposite may in fact be true. Your goal is to cool the motorhome to a certain level. Two units will get you there far quicker and then turn off. One run may have to run twice as long to get you there. I have had units with both. My first Class A was a 32 foot with one unit and I took it to Vegas once in the summer. It was over 100 out and that one AC unit ran solid the entire time and still was unable to make the motorhome comfortable during the day. It was barely able to get us to a comfortable level at night.