I have a Carrier high efficiency heat pump that is about eight years old. I also have a much older, natural gas central unit, that is tied into that duct-work of my home.
This gas unit was part of the original 18 year old system. I know this gas unit is not very efficient because of age, but it is nice to have a working "backup" heat source.
I live in N.W. Alabama so heating is not a major concern but money saved is money earned.
Can someone correct me if I am wrong? ---It is my understanding that generally, a heat pump is the cheapest source of heat to a certain temperature. A heat pump starts to become more expensive when the temperature falls below 40 degrees.
When the outside temperature is 35 to 40 degrees, I use my older gas furnace.
I know there are many circumstances, other then fuel cost, that need to be considered and this is a hard question to answer.
I ask this question because I have only lived in this home for a few months.
All opinions would be appreciated.