On the subject of renewables, I realize that the technologies behind them have greatly improved, but historically, people switched to steam turbines instead of wind turbines because they produced much more usable energy per turbine and per unit of cost.

If we move back to lower-density energy generation, there are some things that (because of cost, timing, or the level of utility that they are perceived as providing) currently use power which will have to be switched off permanently or be reworked to function under limited and intermittent power.