There's been discussion in the Politics of Heating category about how geothermal is not being supported in Congress. This thread is to ask those with relevant knowledge/experience how the numbers pencil out for geothermal on its own, i.e. without government incentives.
Last evening, I watched the latest episode of This Old House. Richard Trethewey has presented such systems before, but for some reason I was more interested this time. Please share your analysis of the following situation.
I own land in Bartlett, New Hampshire. If we build a home on it, the size will be anywhere from 1,700 square feet (minimum permitted by covenants) to around 2,500 square feet (what my wife thinks we "need"). It'll not meet Passivhaus standards, but I'd ensure a very high level of envelope performance, with closed-cell foam insulation and many other design/material features to minimize heat loss.
There's no natural gas available, but every year our homeowners association negotiates with the major local supplier to establish a propane price for anyone in this subdivision who opts to purchase from them. Right now it's $1.64/gallon (last August through the end of July). In addition to a fixed monthly charge of $28.93, electricity costs $0.15/KWH in winter and $0.12/KWH in summer.
What multiple of the upfront cost for hydronic heating with a boiler (either atmospheric and mod/con type - please specify which, but I'd appreciate estimates for both) would you expect for a geothermal system? Assume the drilling would need to penetrate substantial ledge; we're talking about the Granite State, after all.
It's typical in this location to have both central hydronic heat (propane- or, more rarely, oil-fired) and a separate central A/C system. What percentage of the initial A/C system cost might be eliminated if a reversible geothermal source were available? For both heating alone and combined heating/cooling, given today's fuel costs, how many years do you think payback might take, ignoring the cost of money?
Thanks in advance for your replies. I hope that structuring the question this way, i.e. in terms of multiples/percentages, means it hasn't violated the rule against pricing discussions. If it has, Erin, please delete the whole thread.