I showed them the rest of the basement. We had a twenty-seat home theater next door, then four small bedrooms for household staff. The rest of the basement held storage, laundry, and utilities. "We use multiple ground-source heat pumps to heat and cool the homes, the pool, and the aquarium. There is a sizeable solar farm hidden behind trees up on the hill that provides most of our energy needs. An emergency generator sits behind the garage."

"Those heat pumps are expensive up-front, aren't they," Leo asked.

"As isolated as we are, and as big as this home is, we wanted to be as energy-efficient as possible," I said. "We...