Looking for recommendations of a mini split size for my small house. I've got a 400 SQ. Ft. Living room facing west in Seattle (house is 900sq ft total). In the summer my whole house is exposed to direct sunlight all day long. By the mid morning the living room is hot and by the late afternoon it's boiling. This is probably only for a couple months a year but I've got forced air heaters in the wall so the mini split would be used for heating most of the year in an attempt to cut down on electrical bills. The house is well insulated. It's basically a double wide in shape with the front half my living room and the back half two bedrooms. I'm trying to figure out what size system to get for the living room with the hope that some of the cool air will travel down the hallway and aid in reducing the temp in the rest of the house as well but I have limited expectations for this. I'm trying to DIY so was looking at the mrcool DIY series. The 24k unit seems like a great deal but am I going way over size with this? If the living room unit worked out well we might add another in the back master bedroom which would pretty much cover the whole house. If I was doing that upfront it would probably make sense to put in two 12k units. We would keep the in wall heater for my son's room as backup heating in the winter. Any suggestions are very much appreciated. My neighbor paid 7k for the pro install of his system and he has the same house I do. No way am I paying 7k for that when I can run electrical myself and do everything with confidence except charging the lines. That's why I'm looking at mrcool DIY. A local HVAC contractor has 4k as average price of a single zone system. This seems completely insane to me. Maybe if it involved running lines 30 ft and fishing electrical all over the house but for me it's simple to locate head unit on wall and place compressor outside on the same wall. I can easily run electrical from my exterior located panel. I have respect for the trade but in Seattle its highway robbery from contractors right now.

The set up: baseboard hw via nat gas, 2 zone - working great for 20 yrs. Central air whole house one zone added 2011, air handler in the attic and compressor/condenser outside at the side of the house - working great from day one. Switch t-stat from cool to heat back in Sept/Oct and everything has been working normal for months. Wake up New Years Day and the outdoor compressor/condenser is on, not the air handler. I check the t-stat to see if my wife switched the t-stat setting and it's on heat as it should be. Completely shut off the t-stat and outdoor unit is still running. Only way to turn off outdoor unit is pull the outdoor shutoff or flip the breaker in my house's panel. Where do I start investigating myself before I call in a pro? Thanks.