A BATTERY FOR YOUR HOUSE

Tesla’s new Powerwall banks energy in an aesthetically pleasing reservoir so you can power your home with solar energy at night. It is a model of utopian efficiency, if you can afford the set-up costs. The base model is $3 000 (about R42 000), plus half as much again for the required inverters and installation and three to ten times as much for solar panels. But making solar power affordable is not what Elon Musk is after. First he has to make it convenient. The Powerwall offers a way to become energy self-sufficient. If you live in an area with enough sunlight, you won’t pay for power again. Bank what you harvest during the day and use it at night. With less sun, your battery can still top itself off from the grid during cheaper periods of the day. Eventually, you may actually start saving money. But the whole time you’ll be doing something more important: saving the planet.