You can stuff a cheapo window unit in the wall and put in a space heater. But personally I'd go with a combo wall unit that is much better built and will last longer & work better. The link below is to GE, the small wall units with heat pumps are efficient & quiet. Here is a link that might be useful: GE J series

Thanks for the reply tigerdunes. Here's my rationale: Night - bedrooms are same size and doors are closed. So the thermostat in the room should work well to reach comfortable temp in there. Day - door of master wide open and equivalent temp to hallway so should be able to get good temps throughout house. If anything, the supply is a bit bigger for the master as we are planning an addition (master bath/closet) in 1-2 years and he was accounting for that. Still stuck on why the recommendation is always to put in hallway when most people want ideal temp in their bedroom at night

That's a very pretty paint color! I think it turned out nicely. I don't know what your other chair looks like, but I think the white one by the stairs would look nice in the corner with a dark teal throw. Just my two cents' worth.

I am with hubby. I would not want a window-shaker in the bedroom if there is any other way. You have a premium system with the ground source heat pump. Running a window unit might cost more to operate than overcooling the rest of the house. A ceiling fan might be counterproductive. You might be better off letting hot air stratify near the ceiling. High wall mount mini splits don't have to be on outside walls if you can find a way to deal with the condensate. I have 6 on interior walls and the seventh on the outside wall has its plumbing run in the stud space, not directly to the outside. You could also install a small AHU in the top of a closet or in adjacent space. Before jumping into a mini split, do make sure that your system supply and return ducts to the MBr are operating properly. Modifications to your primo GSHP system probably makes more sense than adding. Larger ducts would do it if possible. In addition to that, let's paint with a big brush and see if another zone can be added. Ask around and get recommendations for excellent HVAC pros in your area and then get them in to look at it. On the other hand, a MSHP would be very easy to operate with a small back up generator. That room might be a nice oasis in times of power outage.