Very good idea, my city doesn't have a single (significant) power station in a range of 300 miles.
But talking about numbers, my city has about 600 000 citizens living in, with 6 Electrical substations that can handle a consumption about 480 MW (about 800 GW per Million). The size of them is no more than 5x5, i think (about 5000 - 10000 sq. meters). I think this substation needs to generate about 50 MW to be real (3x4 size), comparing only energy per substation.
But we can compare energy consumption from real world and in-game, It's better to use a USA data, because use of energy is different from country to country. New York used 15.8 GW in Jan. 2015 with 8.5M population = 1,86 GW per million.
In my small city from the game, 43 000 population uses about 320 MW, about 7.5 GW per million (I don't know if all cities uses about the same energy, you can use yours to compare), to be real, I think about 750 MW, but it's very contrary to game design.
Talking about game design, a Wind Power generate about 8 MW. A real one generates only 4 MW.
SO I REALLY THINK THE OUTPUT POWER NEEDS TO INCREASE.
I don't know what the upkeep cost and need to look about real and in-game upkeep costs to generate energy, but for now, I recommend to make it slighter higher than most stations, because the energy was transported though bigger distances and the station has to pay the power station.