Just a thought,

There are lots of ductless split AC units that use heat pump to provide both cooling and heating, some of them are rated SEER25 or above.

I am just wondering any of those have a geothermal hookup to increase efficiency? 

There are water source console units that combine ductless and geo (usually in the commercial section of manufacturers' web sites).
J

Cool, would like to look into it. Which brand were you referring to?

FHP, Water Furnace, Climatemaster......

I want to install a Mini-split, primarily for its 'heat' in spring and fall. I would like to calculate - determine, the temperature when one unit of 'electricity - in' equals one unit of 'heat - out'. I would then use resistance electric heat or (more likely) wood heat. I can use the wood heat efficiently at temperatures below (about) the freezing point. The SEER rating appears (to me) to suggest use, when the output is below the input level. Currently, I use the wood heat, continuesly below freezing and intermittantly above freezing. I want to avoid, re-lighting and temperature swings.

Some of the newest airsource minisplits claim reasonable COPs well below freezing. Check out Daikin and Mitsubishi

Fujitsu 9 & 12 RLN and 15 RLQ (all air source) qualify for fed credit $1500 max on primary residence. Also utility rebates Ive seen as high as $600.00/unit. Mitsu and Daikin make water source commercial equipment. They need 3 phase power and inlet water temps of 50 degrees f and above $$$$