If you have a Nest thermostat, some of the newer models give a usage display of how many minutes per hour they are running. This will tell you how much of your

If you have a Nest thermostat, some of the newer models give a usage display of how many minutes per hour they are running. This will tell you how much of your furnace's capacity is running at. For example, if I have a 40kbtu furnace, and I see a maximum of 15 minutes per hour usage on the furnace during a heating season, that means my usage maxes out at roughly 10kbtu. I might choose my heat pump based on that capacity; if I got a 10kbtu heat pump, I would expect it to be running continuously during the maximum usage time.