Michael Kanellos for Forbes:  The optimism in the energy storage industry is based on soaring demand, rapid technological advances, expanding capacity and, for some, what will likely be a scary competitive environment.

First, the good news. Lithium ion battery packs over the last ten years have declined faster than the cost of solar, said John Carrington, CEO of Stem, which makes behind-the-meter storage systems for hotels and other commercial customers looking to shave peak power costs, during a hallway meeting at Finance West sponsored by the American Council of Renewable Energy this week.

Solar panels have declined by 50% or more in the last five years. Batteries have declined by 80% in three years, he said. Battery packs hit the under $300 per kilowatt hour mark last December, Carrington added. By 2020, battery pack prices could drop to $190 per kilowatt hour. (In 2007, lithium ion battery packs in the wholesale markets sold for around $1,000 per kilowatt hour.)  Cont'd...