I have mine it the garage, last year I could not keep up with the heaters, so in the summer I built a wall, basically making a room in the garage and this year had no problems with the cold, only 3- 200watt heaters on a 350gal tank 500gal total system they go on and off normally as the room stays between 69*/80* depending on the outside temp but the water temp stays stable.
For cooling I installed a small ac, in the summer, it comes on once in a wile and helps not only the water but also the equipment stay cool.
For me the big plus of having all the equipment in the garage is, no worries of spilling water or making a mess and always easy add new equipment when or if you need.