It's the same as English electricity. Today, I went with my housemate to buy some electricity for the apartment. China runs on a pre-payment system. This is handy for me because I would otherwise need a bank account, which is hard for a non-Chinese to get. However, it did mean a one-hour queue at the bank. There were at least 70 other Chinese people in front of us when we arrived. It stretched out of the door and my feet painfully froze. If I had not woken up an hour late, I could have saved my feet.
The whole year's electricity will cost me just £43.33 (650 RMB). Which is a lot less than the large sums of money that I handed over to nPower (British utility company) whilst I was living in Nottingham. Later, I managed to work out that electricity costs three times as much in Britain. It is 3p per unit in China compared to about 9-12p per unit. (Incidentally the units are kilowatt-hours for the technically minded).
So it is not worth buying energy saving bulbs unless you run it for more than 2 hours a day and plan to live here for more than a year. Yes, I was calculating this when I was shopping for light bulbs.