Just a quick note: plus thx to Xringer.
This fall I installed a Gree Crown in my gfs studio.
How's it been working? Our neck of the far north has been taking a beating. The last week has seen lows of -29C (-20F). Every night has come very close to this. Today was a "warm" day. It was a high of -17C.
The Gree has kept her somewhat insulated "studio" warm. We have turned the temp down to 16C. Apparently as low as it will go. To save energy.
Sorry. No delightful graphs accompany my report.
Just saying that this technology works even in the somewhat extreme cold.