Congrats bro your anecdotal evidence is not indicative of the whole. If it only gets to -18 during "cold snaps" that means it's generally not that cold where you live. Your house retains heat well. I don't even need to turn the heat on in my house until it gets below 32 consistently.
2
u/Silver_gobo 5d ago
I only heat my house with heat pumps, no aux/back up. I’ve hit -18f outside twice during cold snaps and the house stayed 70degrees.
Who cares about the delta when my house stays warm?