Dave Sparks uses PV for his ASHP..
Sanyo mini split AC (inverter/variable speed)
With your mild weather, there must be a lot of ASHP users up there.
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If you were grid-tied, you could use any size BTUh and the amount of PV you could afford to buy..
But, being off-grid is a whole can of worms. (Since you can't go without heat when it's overcast all week).
You would need a good battery bank. Or maybe propane heat for back-up..