Around a decade ago, I proudly joined the — then still small — ranks of people in New Zealand with a solar photovoltaics system on their roof. Ours even had a battery, meaning we had an uninterruptible power supply in case of power outages. A fire in a cable trench at the local network company a few months after installation left us as the only house in the suburb with lights and Internet on, and the odd refugee steak from neighbours’ thawing freezers in ours. So far, so good. Sometime not long ...