Tesla, Inc. began development of their Powerwall in 2012, and started production of their first generation version in 2015. Since then, they have developed the Powerwall 2, with increased capacity, and an option for a built-in inverter. The batteries are made of lithium ion, and are designed to “provide energy storage for solar self-consumption, load shifting and backup power” – Tesla. The first generation was rated at 6.4 kWh, with a 3.3 kW peak and continuous power output, while the Powerwall 2 is rated at 13.5 kWh with a peak power of 7kW, and a continuous power output of 5kW. The cost of the Powerwall 2 is listed at $6,200 on Tesla’s web site (includes battery and supporting hardware). The web site also estimates installation costs ranging from $800 to $2,000 (plus tax and permit fees). Tesla also produces the Powerpack, a battery for commercial applications; the Powerpack 2 has a capacity of 200 kWh.