Over the next 30 years, this 6.7 kW solar array, paired with battery storage is expected to offset the homeowners annual energy by 101 percent. The Tesla Powerwall will ensure the family has power when the grid goes down and also allows them to consume more of the solar energy they produce, when their panels aren’t producing power at night. In greenhouse gas emissions, the systems savings is equivalent to saving 161 tons of coal, or driving a car 394,052 miles.