The problem is, selling it back to the grid only works when it's a fairly small fraction of the customer base that's doing it. We can't _all_ sell power back to the grid.

EDIT: Why the downvotes? This is a real issue... The current model of 'buy solar panels and pay for them by selling power back to the grid' will not scale forever...

That really isn't the current model. The current model is to buy solar panels today, thereby locking in your long-term electrical cost at the price of today's solar panels, with the expectation that conventional electricity will continue to rise, with a point 7-10 years in the future where you have "paid off" the panels, followed by 15 years of free/cheap power, avoiding the future high costs of electricity from a utility company, finally ending 25-30 years from now when you need a new system, but hopefully renewable technology will have greatly improved by then.

If the utility is paying a market rate (instead of an inflated rate to get people to invest in alternative energy), why couldn't we all sell power to the grid? Eventually if the home units get efficient enough, what would be the problem with power being supplied entirely peer-to-peer?

Granted, I think we're a very long way away from that, but I don't see anything wrong with the funding mechanism.

The market rate would just fall to near zero. The surplus from different homes would have very similar patterns. When it is sunny and bright out, everyone has surplus. At night, nobody does.

You are buying when everyone is buying and you are selling when everyone is selling.

That isn't even considering reliability. With wildly variable production, we will have to pay out of the ass for peaker plants to pick up the slack.

> The market rate would just fall to near zero. The surplus from different homes would have very similar patterns.

This assumes that all homes are using the same technology to generate power, but after the landrush to solar, rates (which are time variant) would incentivize new entrants to the "sell-to-the-grid" market to choose technologies which might be less average output per unit cost than solar, but which have different timing characteristics.

Most state's do have a sell to grid system for commercial scale.

Though maybe a new type of renewable power that is easily distributed will pop up.

I think the solar rush is mostly because of the subsidies. I think I'd rather fund commercial scale solar.

You are thinking from a large scale, profit-driven perspective.

The early adopters for this, at least in residences, will be people living off-grid, focused on self-sufficiency, and who are willing to take a financial hit to achieve that goal.

Not only will the batteries need to get cheaper, but the available arbitrage opportunity will need to account for the necessary upgrades to utility distribution systems to accommodate large amounts of distributed energy storage (DES). DES, particularly at high penetrations, generally violates the design assumptions of distribution protection systems and requires non-trivial upgrades to protective relaying and SCADA systems to maintain adequate real-time control.

I think it's worth giving Elon Musk the benefit of the doubt. It seems pretty likely that he'd consider these problems before moving forward with a product.

Losing power from snowstorms (well ice storms really) is quite common in New England and many family members have dropped $5k on propane generators. If you can bring this battery down to that price you will catch all those customers as well as have distributed off peak storage capacity. Right now the best way to store power is to pump water uphill, seriously.

'Pumping water uphill' will likely always be a very good way to store power at those scales. I would take a pretty spectacular number of batteries to match the stored energy potential of a small lake with a couple hundred feet of head.

> 'Pumping water uphill' will likely always be a very good way to store power at those scales.

... but not when it's ice.

And does require the right geography