If homebuilders had a magic appliance that could provide an endless supply of inexpensive and environmentally friendly energy, then we would have an excuse to keep building homes without paying attention to how much energy they will use. People who installed the technology could use it as their excuse to consume in excess, and people who didn’t could point to the cost of the appliance as their excuse. (You didn’t think it would be cheap, did you?)
Ideally, the appliance would be produced in a factory and be packaged in a reasonably sized box that could be trucked to the construction site and connected to the building with just a few wires and pipes. It would not be noisy, smelly, or dirty, nor would it use any fossil fuel. If it took some heat from the earth, it would seem like it was using an inexhaustible resource. If most people didn’t understand what it was or how it worked, it would be hard to argue that it wasn’t a good idea. The modern ground-source heat pump fills all these requirements except one: It doesn’t necessarily save energy.