Price, of course. Prices are expressed in cents/kilowatt hour. Plan types include fixed rates and variable rates. Fixed rates offer consistency throughout the plan term, which can run from six to 36 months. Variable rates can change monthly - they're great when prices go down, but not-so-great when they don't. Finally, if you care about your carbon footprint, you may choose a plan sourced by solar or wind energy.
A lot of these financial structures ultimately boil down to being a form of government guarantee, which means that they can’t be scaled up to “solve” countries’ power problems because the governments cannot carry all the liabilities. Countries try to introduce the private sector into power generation precisely to reduce such guarantees, which then end up returning through the back door in the form of government support.
Fixed-rate, long-term (contract) plans provide stability in electricity rates. If market energy costs suddenly trend upward where you live, you can rest assured that you won’t have to pay more out of pocket. However, if you want to switch to a different, lower-cost plan before the end of the contract term, you’ll likely have to pay a cancellation or early termination fee.