I have been considering a new HP as replacement for old forced air split gas/electric system. Problem is, I only have 50 amps available (going to old compressor) without upgrading main electric box.

Average temperature in winter: Dec 60/35, Jan 60/34, Feb 65/38. House is 1200 sq ft with 10-12,000 BTU gas wall heater as backup or supplement to HP.

Question: What happens if I try to run a HP without a backup heat strip?

You`ll get cold when the HP can`t do the job,, without backup,,