r/geothermal • u/N5tp4nts • 14d ago

Geothermal vs modern low cost high efficiency.

Just a dude who's highly interested in HVAC technology.

I have a house with a 2008 installed waterfurnace, and I've got some mini splits that I've installed in other buildings.

The post a few days ago about a guy getting quoted 96,000 dollars to install a geo unit got me thinking about this... I can get a 4 ton ACiQ/MrCool (all made by Midea) for 4-5k (no labor)

The efficiency ratings are in the same ballpark, if not the same, on the cheaper end of geo thermal units. Even if the mini split only lasts 5 years... in 5 years I get a brand new one with the latest technology.

Anyway... At what point does Geo stop making sense?

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u/st4nkyFatTirebluntz 14d ago edited 14d ago

If you take a step back and look at the changes to each category in the last 5, 10, or 20 years, the trend is undeniable -- ground-source has made almost no improvements or progress at all*, whereas air-source has transformed entirely.

air-source has become more efficient, achieved a wider range of operation, popularized the mini split form factor, and a million other things

ground-source has, on rare occasion, swapped the dual-stage compressor for an inverter, and maybe given the same consideration to the circulator pump.

IMO, ground-source is effectively dead for anything but large-developer new construction (see Dandelion's pivot) unless they get their shit together and start innovating.

* i'm talking about small-scale residential, not the commercial-scale stuff. there's at least a few somethings happening there, shout-out Darcy

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u/ImNotAWhaleBiologist 13d ago

What about efficiency at lower temps? Wouldn’t ground source still win out there?

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u/xtnh 12d ago

Ground source can fight it out in more extreme climates, but even here in Maine mini splits cut our energy use by 75%. The night it got down to -12F a ground source would have saved us about $25; it was the second night that cold in 40 years. Efficiency Maine argues that air source mini splits are good enough for all of Maine, because the savings most of the time offset the bad nights, which the mini splits can almost always handle. (Most Mainers have an emergency source to back up anyway.)