I'm confused why you're confused. You pay for energy, not for power. You wouldn't pay the same for a kW delivered for 1 hour as you would for a kW delivered for a whole year, right?
Governments nowadays don't buy a solar plant, they put out a tender "we're willing to buy X GWh of solar power a year for Y years. Solar panels can be placed in area A, and must be removed afterwards. Please quote us a price per kWh."
Advantage of that for the buyer is that, if they get a offer that is too good to be true, they haven't paid the full sum when the seller goes bankrupt.
Also, because the seller has to operate and maintain what he sells, he will think harder about maintenance costs, ease of removal, etc.
Another example of this is the recent auction for a sea-based wind farm in the Netherlands (http://www.offshorewind.biz/2016/07/06/borssele-12-worlds-ch..., 7.27 eurocents/kWh)
Risk for the buyer is that he commits to buy a fixed amount of power at a fixed price over the lifetime of the plant. Worst-case for the buyer, we develop cheap fusion next year, so that electricity prices drop to zero.