Today's question is from Joanne Appelhof. "We now have a geothermal heat pump. It is now 25 years old and needs to be replaced. We are wondering if we should go with natural gas or stay with a ground water geothermal heat pump?" It sort of depends on the kind of geothermal heat pump system you have. If you have a ground loop, that's the most expensive part of the geothermal install. So, really I doubt you would be able to find a gas furnace that will be as efficient as your geothermal unit. Even though a geothermal heat pump is more expensive than a gas furnace, it's not going to be as expensive now for you since you have the ground loop in as it would if you were putting in a new installation. Plus, you can still get a federal tax rebate up until 2020 or 2021, so you should get a geothermal heat pump. There may even be some local incentives so you can save even more. Unless you're having some problems with your ground loop, which would be unusual, I would stay with geothermal. Have more questions? Just ask them in the comments below or on Facebook or on Twitter.