Last year I co-wrote a report for the Wharton School at the University of Pennsylvania about our zero-emission energy future. Yes, the report concluded, it is possible, but hardly easy, for the world to run on 100 percent renewable energy. The biggest obstacle is the intermittency problem — solar panels only work when the sun is shining, and those spinning turbines only produce electricity when the wind is blowing. Is there a solution?

Sure, batteries. So the idea is a big battery pack is your back-up, storing power for use when the renewables aren’t generating. It’s hardly a slam dunk — we don’t yet have the manufacturing capacity for the batteries needed, nor the ideal technology to make it work. Enter Elon Musk, who is poised to announce next week stationary battery packs for home and utility use.

The Tesla Motors CEO sees synergy between his car business and his photovoltaics business (with his cousins), Solar City. That start-up, conceived by Musk and cousin/CEO Lyndon Rive during a visit to Burning Man, is already offering Tesla back-up batteries. And everyone knows Musk and company are ramping up battery manufacturing with their Nevada gigafactory.

Tesla car batteries, like this pack from a Roadster, can be adapted for home and utility use.

Tesla car batteries, like this pack from a Roadster, can be adapted for home and utility use. (Photo: Eric Rosendahl/flickr)

JB Straubel, chief technology officer at Tesla, told an industry event:

It’s pretty amazing how much growth there will be in energy storage. We have to get to a 100 percent renewable grid, and storage becomes an absolute imperative to get there.
That's right, and it's supported by industry observers. Here's what Sam Abuelsamid of Navigant Research had to tell me about Tesla's future:
I think [Tesla's plan] makes perfect sense, and in many respects it is  necessary for the company's long-term future. To some degree, Tesla is transforming from an automaker into an energy storage company. While Tesla has had some success with cars, it  seems clear in the near-  or mid-term that the market for plug-in vehicles remains limited, especially in North America, where fuel prices are likely to remain stubbornly low for the foreseeable future.
The home battery is already hiding in plain sight, as an offering to Solar City customers for $1,500 down and $15 a month over a 10-year lease period, the San Jose Mercury News reports. You can use it to power your house during blackouts (hybrid cars work too), or to store electricity from the solar array.

Does this make sense? Definitely, but pricing is critical. Presumably the gigafactory gives Tesla economies of scale, but there’s plenty of precedent for innovative energy solutions to fail because of price hurdles.   

I once visited the Plug Power zero emissions house in upstate New York, designed to show off-the-grid living with electricity from a home fuel cell running on natural gas. It worked fine, and Plug Power inked a deal with General Electric to mass-produce the cells, but pricing caused the deal to be stillborn. The problem was that the cell produced electricity just fine, but at a price much higher than the grid. It didn’t pencil out.

True believers, in both solar power and Tesla Motors, are going to buy the home battery system, and some already have. The question is whether there are enough early adopters to make a business out of it. The same holds true with the utility batteries. I can see California-based PG&E or San Diego Gas & Electric, both with strong green credentials and solar commitments, ponying up, but the question again is whether there are enough customers for a business. And those pesky price points matter a whole lot.

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Jim Motavalli ( @jmotavalli ) writes about cars, technology and the environmental world to anyone curious enough to ask.