You can plug in a power cart and pre cool the plane with kelly system as well. This is something since day of owning my 182 I have toyed with. I believe without the backup alternator it weighs 49Lbs. My problem is I've used that extra 49lbs more times than I think I wish I had the AC. The issue comes with the dam 182 landing weight (at least for my T model 150Lbs less than the takeoff weight). when trying to haul a bunch of stuff to the keys with enough IFR fuel to to get to a realistic alternate or close places when trying to go with a few friends for a short food hop. The 182 can be a 4 person plane a lot of the time, but on these shorter flights it would sometimes be impossible with that additional 49Lbs thats why I haven't gotten it yet.
However I met up with a gentlemen who had it installed. he took my in his airplane and it was amazing. it has a temperature adjustment so you can actually set the temperature like a modern car. The nice part as someone has already mentioned is you can use it all the time through takeoff and landing, which lets be real is when you want it most! hotter close to the ground with less ambient air flow. If i were to get a system it would be this one but I just have a hard time justifying the weight.