Does anyone have a suggestion? I'm trying to decide whether to maintain an old geothermal, replace with a new one or change to natural gas. Is there a site or source you’d recommend to do a btu evaluation? I have a 1981 4 bedroom contemporary 2 1/2 floor home of nominally 3700 sqft, with 6” thick walls and soaring (9-22) ceilings in the 250 sqft hall and 4-500 sqft living room. This makes “sqft” of limited value; is there a cubic foot calculation? I just bought the home and have been shocked by the cost of heat and A/C in our first 6 months. The home has open system geothermal Florida Heat Pumps, 4 and 5 tons, I think. I don’t know what has been replaced over the 29 years, but I just replaced the fan and the well pump recently. With the estimated life of a 1981 system, I know it’s time to upgrade. My problem is that, without even adequately heating, or air conditioning to extreme, my electric bills have peaked at $1500 per month and average out to about $1050. Could a new, more efficient geothermal make enough difference to merit the expense? Please feel free to transfer this to the blog if you prefer..and know how. Or if you instruct me how I can register and post it, I’d be happy to. Thank you for your intelligent and reasoned replies to the other members of the blog.