How hot is hot when moving from class a/b to to a or tubes?

Its all relative. For sure SS Class A runs hotter than A/B. Digital amps run cooler. Tube amps run usually hotter than all three, except perhaps for ghdprentice, but, for example I run a 40wt tube amp 10 to 12 hours a day. Puts out a bit of heat but really doesn't warm my house much as far as I can tell, nor does my A/C bill run high. The up side is in the winter I keep my house at 68 degrees and if my hands get chilly I just walk over and put them on the transformers, not the tubes!).  My expense is I go thru a quad of tubes every year and that can be a bit pricy, but it was worse when I ran a big tubed amp and it was two quads. The enjoyment I get from music greatly exceeds the small additional costs involved in running the equipment.  

Also, on warm up. It depends. I could talk about the warm up on the previous versions of Audio Research preamps, in great length. But I really don’t notice much of any with the current Reference models. While earlier warm ups were only 10 to 15 minutes. I’m just not hearing any with contemporary amps and preamps. It used to really stick out… you could not help hear it… but today I am just not hearing it. There may be a little… but if so, really subtle.

I live in a suburb of Memphis TN, gets very hot here during the summer. I have 2 tube integrated amps in my main system which is in a 25x19 foot room so smaller than yours mpoll1. One of the integrated amps is 845 tube based; the other 7189A/EL84M .  It doesn't matter what the season , neither, and most specifically the 845, never leave me feeling that they are heating up the room; nor that the AC runs more in the summer because one or the other are on. Likewise,  I have a KT88 integrated amp in my upstairs family room with similar footprint and that also doesn't heat up the room. Net net, your room is bigger than either of mine and I wouldn't think twice about the "heat issue" in your case.  Cost wise I haven't ever attempted to size up the utility cost factor whether using tubes, or class A/B amps; I'm more interested in musical enjoyment.  I will agree that the tube amps sound better after 30 minutes or so, and I begin listening after allowing the tubes to initially warm up for 10 minutes or so.

I had a pair of Monarchy Audio se-100 Delux class A mono block amps.   They powered a pair of Usher floor standers.   Even at moderate volume the amps barely got warm.   Amazing amps for $900 I bought as factory refurbs/upgraded.    I once brought amps to my friends home to power a pair of Maggie’s.   The amps definitely ran hotter to the touch but not extremely hot.  So in my situation guess it depended on the speaker load

@mpoll1  I have been running two 50 watt tube mono blocks.  See my virtual system to get an idea of the size.  To answer your questions.

Ready to play as soon as I turn them on.  No great warm up period required.  

After they have been running for a while, and at med loud load, the transformers are running at 110 degree Fahrenheit.  My room is 13 x 21.  After two hours of listen time the amps have raised the room temp by 3 - 5 degrees. 

The cost of running tubes vs SS  a few dollars per months.  My SS amps pull 3 amps on average and the tubes pull 6.  I doubt you will notice a difference on the electric bill.