You don't say where in Cali you are but I'll assume you are going to camp inland where we need AC in the summer. My advice: get the smallest one they make. If you want to read why I say that read on.
I have a small 23' TT with a 15k AC. Factory either made a mistake or didn't have a 13.5 in stock when they put the AC on the TT I ended up buying. In 2006 I bought my first Honda EU2000. It would not power my AC (obviously). Even camping in Temecula in August the 15k was way overkill for my trailer. So...
I made an appointment at Camping World to have a smaller BTU AC put in. I think the one I was planning on at the time was 7500BTU's. The price for that was hundreds less than a second EU2000 and after selling the 15k my out-of-pocket would have been very manageable.
When I arrived at my appointment the service counter guy talked me out of the smaller AC and recommended I get a second EU2000. He convinced me a 7500 would not be enough to cool my trailer. Wrong. I got my second EU2000 from Wise and glad I did. But, I certainly didn't need to go that direction.
I've camped in 109 degrees in the desert and only needed the Low setting on the 15k AC in my little trailer. My brother had an 815 like yours and he never went past Low on his 13k. So, again, get the smallest one you can find. I like the little Polar Cub.