My shop is 23' x 32.5' (747 sq ft) in a basement with 9 foot ceilings. It is a daylight basement with one 32.5' wall exposed. That wall is 2x6 construction insulated with sheetrock on the interior and brick on the outside. The exterior door is insulated and the exterior window is double pane glass. Two walls are concrete block underground with no insulation. One 23' wall is a 2x4 interior wall, insulated with sheetrock on both sides. On the other side of the interior wall is conditioned space. The shop ceiling is also insulated (6" batts, no sheetrock).
In 2013 I installed a 12,000 BTU Mitsubishi model MSZ-FE12NA indoor and MUZ-FE12NA-1 outdoor unit ductless split system. It has a 7 year compressor warranty and 5 year warranty on other parts. Per the dealer/installer it would use less electricity than a 60 watt light bulb. We noticed no change in the electric bill after installation and with the basement conditioned, we noticed the kitchen above the shop is more comfortable in winter. HVAC company suggested a lower BTU system (9000 or 10,000 as I recall) but I went with the larger 12,000 BTU system just in case. Based on my experience to date, the smaller system would likely have worked.
I'm delighted with the performance of the system. In winter I am a comfortable 70 degrees, even when the outside temperature is 15 degrees. In summer I run the system at 74 degrees. The system cycles on and off less frequently than my house Trane heat pump. Plus it is extremely quiet inside and outside. The outside unit is installed next to my deck. Standing or sitting on the deck the dryer vent positioned next to the split system unit is louder than the split system. As mentioned previously the system is much more efficient than a ducted air heat pump.
No issues conditioning the entire space from one interior unit positioned above the window on the outside wall. Temperature is uniform throughout the shop. I have a double door to the exterior of the shop through which I move materials and equipment. The system recovers quickly from the door being opened and closed frequently on hot or cold days.
The system came with a remote control unit and wall mounted bracket for the remote. This is a very handy feature.
I do run a portable dehumidifier during the peak summer months. Even with the split system running I fill a 70 pint bucket in a 24 hour cycle. My understanding is that mini split systems are not as effective as ducted air heat pumps in reducing humidity. With the dehumidifier running, the humidity in the shop is about 42. Without it is about 68. I do not run a humidifier in winter months.
No repair issues in 4 years of operation. The only maintenance is cleaning the filter every 6 months. If I ever build another shop, it will have one.
