Which consumes less battery: Wi-Fi or 2G data?

I just want to know what consumes less battery Wi-Fi or 2G Data. My battery last long for 12- 16 hours only. I know there are lots of application which continually running and fetching data from internet. I have both options available, in my office i have Wi-Fi and i also has 2G plan in my sim account, both give me desire speed.