for me, being at a rv park or campground while paying for the amenities, such as power, is like being at a hotel - if the hotel loses power for more than a certain length of 'comfortable' time, several hours, it makes sense that they would then refund you any prepaid time if you have to leave -
while it's not 'their' problem that the power went out, you DID pay for the amenities you expect, and therefore if they cannot deliver, you should be refunded.
A campground which offers electrical power at each site, or water, or sewer, is the same. If they can't 'deliver' that amenity, then they certainly shouldn't be able to hold you to an extended stay you paid for simply because it is 'out of their control'.
Insurance is designed to pay for these exact issues that businesses may encounter - loss of power by their utility. Business income then suffers because they can't do the 'business' they are being paid for. You, as a paid camper, should be able to get your refund, even for the days you 'stayed', not knowing 'when' power might be restored. You wasted fuel in your vehicle, or fuel in your generator, which is not 'free'.
Yes, you can just 'leave', and hope they do the right thing, but if you're not there physically to 'fight' it, it's doubtful. I would keep barking until you get the answer they should be giving you - a full refund for each and every day you did not have power for at least 75% of the day, and the days you are not going to be staying, since they can't guarantee that it's not going to continue happening.
You should not be to one losing money due to a power outage, THEY should.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada - Northwest, GA! (also, '14 Gulfstream Amerilite and '07 ForestRiver Rockwood) : )