https://www.wired.com/story/cheap-at-last-batteries-are-making-a-solar-dream-come-true/

Todd Karin was prepared when California’s largest utility shut off power to millions of people to avoid the risk of wildfires last month. He’s got rooftop solar panels connected to a single Tesla Powerwall in his rural home near Fairfield, California. “We had backup power the whole time,” Karin says. “We ran the fridge and watched movies.”

Californians worried about an insecure energy future are increasingly looking to this kind of solution. Karin, a 31-year-old postdoctoral fellow at Lawrence Berkeley National Laboratory, spent just under $4,000 for his battery by taking advantage of tax credits. He's also saving money by discharging the battery on weekday evenings, when energy is more expensive. He expects to save around $1,500 over the 10 years the battery is under warranty.