A customer called me last winter, frustrated. He had bought four 12V 100Ah deep-cycle lead-acid batteries, wired them for 48V, and connected them to a 5,000W inverter. His plan: power the furnace, fridge, lights, and router through a 2-day outage. The math on paper said he had 4.8 kWh of usable capacity, and his daily critical load was around 4.5 kWh. He should have had just enough to scrape through 24 hours.
A neighbor flagged me down last month, holding a melted power strip in one hand and a sheepish look on his face.
“Surge protector failed,” he said. “TV is fine, though.”
Tesla is the default answer. Someone hears “home battery” and thinks “Powerwall” — the same way people used to say “Kleenex” for tissues. That brand recognition is earned. The Powerwall 3 is a genuinely good battery: 13.5 kWh, 11.5 kW continuous output, integrated inverter, clean industrial design, and the Tesla app experience that the rest of the industry is still chasing.
On April 28, 2025, at 12:33 PM local time, the lights went out across Spain. Not a neighborhood. Not a city. An entire country — and then some.