Apparently it wasn't just empty talk when Elon Musk and his cousin Lyndon Rive, CEO of SolarCity, said that "within 10 years, every SolarCity system will come with batteries from Tesla's Gigafactory". Tesla's new Powerwall home battery has barely been announced that SolarCity is already saying that it will offer it as part of its 'turnkey' system, along with solar panels and control systems.

In a blog post, Peter Rive, SolarCity's CTO, reiterated the vision that storage would soon become a default component of his systems: "Using Tesla’s suite of batteries for homes and businesses, SolarCity’s fully-installed battery and solar system costs are one-third of what they were a year ago. We expect costs to continue to decline as manufacturing scales, and over the next 5-10 years, these cost reductions will make it feasible to deploy a battery by default with all of our solar power systems."

© SolarCity

While SolarCity will also offer battery storage to its commercial and utility customers, it's the residential option that interests us most (sorry, corporate TreeHugger readers -- we love you too!). The general idea is pretty simple, as you can see in the diagram above: During the day, solar panels on a house will often produce excess energy. This can be stored in the Tesla Powerwall battery for use as night, as you can see below.

© SolarCity

This further reduces the need to draw power from the grid, and that's good, because the power from a house's solar panels is clean and has a marginal cost that is zero, so the more you use, especially at peak time in the evening, the better.

The battery also provides a backup during power outages, potentially replacing noisy and dirty diesel generators.