Upgrading air conditioning capacity when an RV only has one 15,000 BTU/hr A/C usually means adding a second A/C unit, but more often than not RVs that have only one A/C from factory come with a 30-Amp service, and if it's a Class A or Class C motorhome with a generator it will likely be an Onan 4,000-Watt size.
We know that upgrading electrical to 50-Amp service is one option that works, as is upgrading to a 5,500-watt generator. These upgrades essentially allow air conditioning capacity to be doubled by adding a second A/C. This is expensive, and may be unnecessary since too much A/C capacity isn't necessarily a good thing anyway.
The other often-reported approach that is inexpensive and works well is to add a second A/C and run it separately from the campground's 20-Amp circuit at the pedestal. The main limitation with this approach is that the 4-kW generator may not run two standard A/Cs if tailgating or boon-docking (i.e. -- without shore power).
Often it is said that you can't run two A/Cs with a 30-Amp service, but that assumes you have two large and inefficient air conditioners. There is no doubt whatsoever that a 30-Amp service can't run two 13,500 or 15,000 BTU/hr air conditioners like the cheaper units often supplied by manufacturers. Simple math confirms that.
However, all A/Cs are not the same -- in capacity or power requirements.
When we looked at a used 30-foot Class A with one A/C a year or so ago, I also looked at options to upgrade air conditioning that could still run from 4-kW Onan so we could tailgate in summer, and determined (from specifications) that I should be able to increase A/C capacity by approximately 50% by going to two new high-efficiency 11,000 BTU/hr Power Saver A/Cs. Further research on RV forums revealed various owners have successfully run up to a 13,500 and an 11,000 BTU/hr high-efficiency A/C on a 30-Amp service.
The numbers show it should be possible, and it's already been done to confirm it will work under the right conditions, but it creates compromises that may be difficult to accept depending on how RV is used.
Please brainstorm away, both Pro and Con.
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