Sorry RP.

My 35 degrees is based on most of the load calculations I do a nd the
high and low temperature ratings of the heat pumps I use. Sometimes
the balance point is as low as 30 degrees outdoors, but I have never
seen a balance point of 20 degrees. But I am basing that on the
climate in Myrtle Beach, SC. Apparently in your part of the south the
balance point is different. I suppose the ocean has a moderating
effect on the outdoor temperatures around here. Every climate has it's
own balance point. Best to do your own calculations.

The heat pumps that I checked for that COP of 1.5 @ -20 degrees were
rated 12 to 13 SEER and 7.1 to 8.5 HSPF. 10 SEER units would be lower
in HSPF and heating COP as well.

Stretch