Wireless N also uses on avg 3x more power to run. We might be lucky and they some how figured out a way to reduce the power consumption but that will just reduce its benefits. Here is a good resource for entry level info.
802.11n FAQ ? AirTight Networks
For the more advanced user:
http://ils.intel-research.net/uploads/papers/80211n_power.pdf
Do not worry about power consumption in my house,i was not sold on N till i got the ipod touch and was amazed at the speed and range difference over G.same goes for my customers Laptops that have N..