When you have production at a power station, your problems only start. You need to carry that power somewhere, and it takes time.
Also, you have to upgrade every path between the power station and your data center. It's not like flicking a switch. Your standard power budgeting doesn't take a multi-megawatt data center into account when it's first made.
And power budgeting is not on paper only. It affects from power generation schedules, demand curves, infra planning, etc. It changes literally everything.
I'm a sysadmin at a multi-megawatt datacenter. We work with authorities for finding solutions, plus we also provide computational support for calculating generation schedules across the country.
We let Westinghouse die and now all boo hoo no power.