A new battery could “change the way the world uses energy,” according Elon Musk, whose company Tesla Motors Inc. developed the product. The system is called Tesla Energy, and it has the potential to make homes free of fossil fuels. The batteries can store energy from solar panels, which can then be used to power the home. The smallest battery is called Powerwall and can be hung on the inside or outside of a home. The system weighs 220 pounds (99.8 kg) and is 7.1 inches (18.03 cm) thick. It costs $3,500, and at a full charge can run a few household appliances for several days. The system is also useful in case of a power outage. And that is just the smaller system. Powerpack is the larger system, and that is 10 times as powerful. Powerpacks can be used together in infinite amounts, making no application out of reach. At the Tesla Energy announcement in April, Musk boasted that the entire event was being run off the batteries.