Country Geek
Gold Member
I currently have an electric heat pump with propane backup heat. I'll be replacing it with a geothermal system in a few weeks (currently planning the layout now).
It's important to understand exactly how an electric heat pump with gas backup actually works, because it's often glossed over. Unlike an electric heat pump with resistance heat backup, the gas backup heat doesn't supplement the heat pump, it replaces it. The two do not run together. It isn't even sensitive to how well your house is being heated. A gas backup system has an outdoor thermostat and when the outdoor temp gets down to a certain level (35-40 degrees seems common), the electric heat pump switches off and the gas furnace heats the house. So for all practical purposes when it gets cold out you are heating with a pure propane furnace.
I strongly recommend that you download and run this spreadsheet before making any decision on type of fuel, especially if you are considering doing anything with propane. http://www.eia.gov/tools/faqs/heatcalc.xls. People like to talk about how expensive a regular heat pump is when the electric resistance heat strips kick in, but get the real numbers. I worked them using my local rates and prices and found that propane is so expensive it simply isn't competitive. I found that in my area, the propane backup costs more than the electric resistance backup when the price of propane exceeds $2.20 a gallon. Which it consistently has every winter for last several years. And don't forget, with propane backup, you're running on pure propane heat, not simply supplementing a more efficient heat pump like electric resistance backup does.
Just an anecdote, a friend of mine complained during the polar vortex January that his electric bill went up $200 because of all the resistance heating that his electric heat pump was using. Sounds bad, but for that same month, my propane bill was $850(!).
The tax credits and rebates make geothermal very attractive and can bring geothermal down to the price of a conventional system or even a little less. As others have said they are quieter and more efficient, but hey also last longer... 10 year parts/labor and 50 year parts warranties aren't that uncommon. Also, at least around here, geothermal systems don't require any kind of backup heat unlike air source heat pumps. This is because the ground temperature is relatively constant so the system can always develop heat from the ground, which can't be said for an air-source system.
Another thing to consider that hasn't been mentioned is refrigerant. With a 25 year old system, you are likely using a type of refrigerant that has been or is being phased out. You will still be able to get it after next year, but at a rapidly escalating price as they will not be making any more, to the point where refills may not be economically viable. So in my opinion if you have an economically viable opportunity to replace the system now, you should do it.
Sorry for the long post, but since I'm in the middle of doing a replacement now, I can identify with this thread.
It's important to understand exactly how an electric heat pump with gas backup actually works, because it's often glossed over. Unlike an electric heat pump with resistance heat backup, the gas backup heat doesn't supplement the heat pump, it replaces it. The two do not run together. It isn't even sensitive to how well your house is being heated. A gas backup system has an outdoor thermostat and when the outdoor temp gets down to a certain level (35-40 degrees seems common), the electric heat pump switches off and the gas furnace heats the house. So for all practical purposes when it gets cold out you are heating with a pure propane furnace.
I strongly recommend that you download and run this spreadsheet before making any decision on type of fuel, especially if you are considering doing anything with propane. http://www.eia.gov/tools/faqs/heatcalc.xls. People like to talk about how expensive a regular heat pump is when the electric resistance heat strips kick in, but get the real numbers. I worked them using my local rates and prices and found that propane is so expensive it simply isn't competitive. I found that in my area, the propane backup costs more than the electric resistance backup when the price of propane exceeds $2.20 a gallon. Which it consistently has every winter for last several years. And don't forget, with propane backup, you're running on pure propane heat, not simply supplementing a more efficient heat pump like electric resistance backup does.
Just an anecdote, a friend of mine complained during the polar vortex January that his electric bill went up $200 because of all the resistance heating that his electric heat pump was using. Sounds bad, but for that same month, my propane bill was $850(!).
The tax credits and rebates make geothermal very attractive and can bring geothermal down to the price of a conventional system or even a little less. As others have said they are quieter and more efficient, but hey also last longer... 10 year parts/labor and 50 year parts warranties aren't that uncommon. Also, at least around here, geothermal systems don't require any kind of backup heat unlike air source heat pumps. This is because the ground temperature is relatively constant so the system can always develop heat from the ground, which can't be said for an air-source system.
Another thing to consider that hasn't been mentioned is refrigerant. With a 25 year old system, you are likely using a type of refrigerant that has been or is being phased out. You will still be able to get it after next year, but at a rapidly escalating price as they will not be making any more, to the point where refills may not be economically viable. So in my opinion if you have an economically viable opportunity to replace the system now, you should do it.
Sorry for the long post, but since I'm in the middle of doing a replacement now, I can identify with this thread.
