CAN be very expensive. If you are doing it with a car radiator and a hose pipe it costs very little and there isn’t even a heat pump involved.
You can take it up a step by using a heat pump of course. Which you can also do fairly cheaply if you are willing to modify a portable AC unit or tbh anything else with a heat pump in it. All you need to do is water cool the hot side of the heat pump and send that water through your ground loop.
Depends how much you want out of it. Are you heating and cooling the entire house year round along with providing hot water. Or are you just taking a few degrees off the peak summer temperature in a room or two?








Pretty sure it doesn’t make much sense today. £100 a year just to have a connection and that is before you even use it for anything.
Heat pumps are far more efficient so even before the electricity tax cut its cheaper to run. Then the savings on having a gas connection too are huge.
And for steak fans who think gas is necessary, charcoal/wood is better. £100 a year would buy a massive gas canister for cooking over, or a massive delivery of firewood.