The POWERWALL 2 from TESLA is the best known battery for solar energy storage worldwide for good reason. It is arguably the most advanced system that can be adapted to any solar system, whether 3-phase or single phase. It can be installed at the time the solar system is installed or it can be added later. You can also add this battery even if you don’t have solar. The POWERWALL connects to the grid, the solar system and the battery through a module known as the GATEWAY. It allows you unparalleled control of your system for monitoring and also for modification of charging and discharging times and parameters. The POWERWALL will operate in the even of a grid failure. Each POWERWALL 2 has 14kWh of energy storage of which 13.5kWH can be used. You can add more if you require additional storage. The POWERWALL can discharge at a high rate to power most appliances in your house, 5kW continuous and 7kW peak. Each POWERWALL battery costs $10,000. The GATEWAY is an additional $2000 and installation is $2000. Additional batteries do not require additional GATEWAY modules.