I think you are missing the big picture here. Geothermal makes the most sense in new builts, since it avoids the costs of a conventional systems for heating, cooling and domestic hot water. We are transitioning away from fossil fuel, which means the heating section, which is the second largest emitter after the transportations sector, will have to be electrified. This will happen in the next 20-30 years, with new built houses being the first where zero emissions will be mandated by building code within the next 5 years, with the retrofit market following about 5 years later. If I am looking at lets say NY State, that is already law that everything has to be carbon free by 2050 when it comes to heating and transportation, with steps for its implementation.Pretty much everything will be electrified, since that is the only form of energy currently which can be generated renewable and without emissions. Connecticut is a bit behind with state regulation, but they have set things in motion. https://portal.ct.gov/DEEP/Climate-Change/Connecticut-Legislation--Executive-Orders-on-Climate That leaves ASHPs and GSHP, or some crazy guys which use electric resistance. On a large scale, unless you live in a warmer climate zone (much warmer than Connecticut or New York State), you cannot implement ASHPs. The issue is not overall annual efficiency, the issue is peak. ASHPs simply loose their efficiency and capacity in the coldest hours of the year, GSHPs do not (at least by far not to that degree). ASHPs discharge the heat in the summer into the atmosphere when it is least efficient, only to extract from the air during the coldest days of the year, also when it is least efficient. GSHPs put it into the ground, where it is stored, and extracts the heat 6 months later. The loop acts as a buffer storage. The loop is an amazing storage devise. Imagine we would have solar with a battery which can store and supply all the energy needed for 6 months, with a 6" footprint (diameter of the borehole). We would not have a grid anymore... If we lower the loads of the house, great, we need lesser bore length and a much smaller ground source heat pump. And much smaller ductwork or heads in in terms of a split system. Which will make it much cheaper to install. Lean but mean. Gas is not cheaper, gas is simply subsidized and socialized. The costs to connect a house to gas is rate based and spread out among all the rate payers, at enormous costs per household. But that infrastructure and those legacy rules are being phased out, and simply not an option anymore. It is actually the costs which drives this transition, in addition to the climate benefits.