You can optimize a powerplant for efficiency a little more than you can an automobile engine, because it doesn’t have to move, runs at one speed all of the time, can be more flexible as far as cost, etc. Hydroelectric dams aren’t heat engines, so their “efficiency” is like 98-99%. The newest natgas gas turbine - steam turbine combined cycle plants are pushing 70% efficiency.
“The newest natgas gas turbine - steam turbine combined cycle plants are pushing 70% efficiency.”
The cost per BTU is much less than that for oil and gasoline.