bigethan -- that's not necessarily how it works. It does work differently in different state & local markets, so it's possible that there's a market that works that way. I don't know of any, personally.
Usually the deal is something called a PPA -- Power Purchase Agreement. It's usually set up that you agree to pay some fixed price-per-kWh, and that price escalates by some regular way over the life of the contract. That price could be higher, or lower, than the prevailing rates for electricity in that market, and that escalator could be higher or lower than rates at which energy prices increase -- but either way, they're locked in from the start.
Usually the deal is something called a PPA -- Power Purchase Agreement. It's usually set up that you agree to pay some fixed price-per-kWh, and that price escalates by some regular way over the life of the contract. That price could be higher, or lower, than the prevailing rates for electricity in that market, and that escalator could be higher or lower than rates at which energy prices increase -- but either way, they're locked in from the start.