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."
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.
SolarCity is currently working on building a 'solar gigafactory' in New York state to produce its own high-efficiency, low-cost solar panels, using technology from Silevo, a solar manufacturer that it recently acquired. With Tesla working on its side to reduce the battery costs with its own gigafactory in Nevada, the total system cost of residential solar isn't about to stop going lower.
Rive also writes: "Batteries distributed at homes across a region can lower the costs of maintaining the grid and new market structures designed to take full advantage of this benefit appear likely in several states. [...] I believe the best grid design is one in which utilities embrace distributed energy resources. However, when utilities and regulators impose solar-specific charges on their customers, or burden homeowners with unduly long system interconnection delays, utilities risk mass customer defection from the grid via solar battery systems."
A few years ago everybody was talking about "smart grids". We might be hearing less about them now, but they are becoming reality with this kind of stuff. It's possible to imagine a future where most roofs everywhere have solar panels, and most buildings have some batteries tucked in some corner, and most of the energy we use comes from clean, renewable sources.