If you are having this conversation and can afford the boat with AC(and a genset, dockside AC is just a tease), get the boat with AC. You will not regret it if you get it. If you do not get it, and you could have gotten it, that fact has a good chance of ruining your trip!! Further to that point, if you have non-sailors/non-campers aboard, they will have a better time with the AC!
As to how much you will use it, that depends. I can tell you how much I use it. Disclaimer: I charter
with Moorings/Sunsail, the fuel
If there is no wind
or if it threatens rain, I run it all night.
If it is windy, I usually run it for a couple of hours in the evening to "undo the damage of the day" and then open it up before bed
. I will also run it for an hour or two in the morning while cooking
breakfast etc. I cannot tell you how nice it is to put on sunscreen and have it dry completely before I start to sweat!!!!!
Another benefit of having a genset and ac is that you get some benefit while you are charging
batteries: you cool off. Further to that point, you don't have to run the engines for charging!!!
On my last BVI charter
, we moved every day and averaged less than 1 hour of engine
time per day. This was only made possible by the genset which kept the batteries topped up.
Bottom line, I recommend AC