Most of the numbers floating around the internet and nearly every mainstream news piece about bitcoin's energy consumption are wrong. They cite an outdated statistic maintained by blockchain.info that assumed everyone was using a GPU even when nearly all of the network was ASICs.
I would estimate the current network (25Ph/s) averages around 2-5W per Gh/s, leading to 50-125MW total power use. bbosh in this thread is off by an order of magnitude.