Sorry misread your post, a mini split is just a small unit that has a "cassette" for the evap inside and a small condensor sitting out side, they were made for cheaper installation with no duct, they were first and still called ductless but mini split has becime the proper name now

Our gun club has a Mitsubishi ductless unit hanging on the wall in the clubhouse. Very quiet and does a good job of heating and cooling the large room.

i noticed those mini split systems have poor seer/hspf ratings
near bottom ratings

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Those are kind of a DIY model, Daikin (Made in Houston) have ratings up to 23 SEER + as do other companies



But a SEER is a pretty pencil whipped rating kind of like EPA MPG on cars SEER is Seasonally Adjusted energy efficiency ratings, an EER is Energy Efficiency Ratings .they are much more accurate but the giverment likes the SEER




But super high SEERs also have problems, to get the super high numbers the indoor coil is quite warm, and warm coils don't dehumidify in the cooling cycle very well so people tend to drop the stat setting so the savings goes down, we had that problem back swapping out 6 EER units for 9+ eer, people would call us back saying it isn't cooling because it feels clammy in the house, just a warmer evap coil

Around here NG heat is about 1/3 the cost of electric resistive heat or propane. A mini-split heat pump heats at about 1/3 the cost of resistive heat (that's where the 300% efficiency comes from). So the actual running cost to heat with NG or heat pump is about the same. But a mini split also cools. I dont know how much it costs to install a vented NG heater but a mini split for 350 square feet is a DIY project. And they have wifi control. You're at work, get off in 3 hours and want to use the shop...just use the app on your smart phone to tweak the temp.

I hope to install a mini split this summer. I need cooling as well as heat and don't have easy access to NG (gotta run a line and install a vent, not DIY for my skill set). Mini split needs a 3" pass-through hole and plugs into a 120ac outlet, I got those skills.