Sticking a battery on your home solar system seems like the simplest idea in the world. You could use it to ride through power outages, or run appliances on stored solar power when grid demand is peaking to avoid brownouts or earn cash back on your power bill. You could even charge your plug-in car with it.
But at what cost? So far, home battery makers have been unable to prove their systems can compete with the grid’s cheap and highly reliable power. Why pay thousands of dollars for backup batteries when the power only goes out twice a year?