The roof of the old mansion was interlocking slabs of slate, set into exquisitely-carved masonry. God knows how much it had cost, but it would probably last half a millennium. And here I was, ruining it by making holes all over the place to mount solar panels.

The diamond bit on the cordless drill bit unhappily into the hot stone. We’d run two batteries dry already, and we weren’t even half done. The owner of the house wanted seven kilowatts worth of photovoltaics, which meant we had a hell of a lot of surface area to cover. Clouds gave us some brief moments of respite from the summer sun, but a noisy central air unit seemed to be blowing hot wind directly at the ladder every time we scaled it. Christ, that thing would probably use all the power by itself just keeping the place cool. Even worse, a few yards away was a heated swimming pool. You could put the hot end of the A/C in there; gain a bit of efficiency, I thought.

It began to rain; big drops sizzling and drying on the rooftop. Time to head home.