A GTHP does several things. First the summer SEER is 35+ and you get free hot water from the desuperheater. The winter heating is easy as the COP is 4+ and you get hot water as well, but not as much as in the summer.
Ingrims is the key. A 36 K BTU/hr GTHP for $3400! Misc supply PVC is another $300 or so and you can glue this together. Then some supply boots put in before you do the slab. This is easy work.
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The minisplits are great, but they don't seem to last that long . . . . .
Some of my GTHPs have been going since 1991 with no fixing at all (except air filters).
Steve