This technology has been around for some time, but it fails to generate much PR. You can get a measley $8000 US federal tax credit for installing one. A few enlightened states (not mine) will give you some additional tax credits for installing one.
The expensive part seems to be drilling the earth and laying the hose. However, what they fail to mention is that once its installed, it will last 50+ years.
The parent also mentions open and closed loop, but fail to talk about direct exchange aka DX, which would make more sense for a lot of people.
"The direct exchange (DX) system is a series of copper tubes buried 4 to 6 feet below ground level. Refrigerant gas is then fed through these tubes creating a direct heat exchange between the temperature of the ground and the heat transfer medium, which in this case is the refrigerant gas. Because of this direct exchange feature these systems operate at considerably less operating cost than water source systems and because they do not require the additional water pumping cost and, DX does not suffer the heating or cooling loss associated with transferring the water temperature to the refrigerant as is common with these systems. DX is also cheaper and easier to install as it requires no well drilling or plumbing costs. As copper is a more efficient heat transfer medium than PVC pipe as found in water source, trenching costs are less due to less ground mass being required by DX."