Actually the shield system on Hoth would have been a little different to that on Endor, after all that shield was being projected far out into space to encompass a facility the size of a small moon requiring the massive shield projector array used by the Empire there.

By comparison the shield system on Hoth was a localised shielded area which would have required a number of shield generator modules dotted across the frozen wasteland that made up the territory surrounding the Rebel Base. These would have been considerably smaller and probably camouflaged to make them harder to detect, their design would be akin to shield generator blisters on capital ships.

So is there a shot in the movie where the gun was locked on to the round backbone-looking building and had the words "power generator" underneath it?  I ask because what they say and what things look like in star-wars has been proven to be wrong before.  I can easily point to the giant bubbles on top of the super star destroyer in RotJ.  We see those destroyed and the very next thing that is said is "the shield generator is down."  Lucas later admitted that those aren't shield generators, yet all of us thought they were.

Same with this here.  They blew up a target then the next message was "their shields are down, you may commence your landing."  Whether you want to argue the semantics of if it's a power generator or a shield generator, what everyone will believe is "if you shoot the funny round thing, the shield generator is dead."  As such I don't actually think it matters whether we call it a shield generator or a power generator, however my inclination is to call it a shield generator because that's what everyone associates it with.  And even if they are power generators, again, in RotJ Han destroyed the power generator for the Endor shield yet we still saw the shield generator explode.  It seems that in the movies, no matter what you destroy it's going to be a shield generator

Interestingly Star Wars: Force Commander (one of my all-time favorite RTS games) had them as shield generators.  You could put them down and everything inside their "shield bubble" would gain shield ability.  As such even lucasarts has made this discretion/mistake before

I loved that game.  It was so great.  Multiplayer was also the best.  Except for when my kid brother discovered that you could rename troops to whatever you liked.  He would constantly rename single infantry men "Woodrow" and marched them up into the firing line to be "executed" to demonstrate what was going to happen to me

Fear the Woodzilla

I don't feel I really have that much knowledge about the sw universe to jump in here, but I did a quick qookiepedia search and found all evidence pointing to THX-1138 theory. A search for shield generator http://starwars.wikia.com/wiki/Shield_generator and you see something similiar to what Han blows up on endor. Power generator didn't have any picture though. http://starwars.wikia.com/wiki/Power_generator