Current power consumption
You can monitoring your energy consumption with :

iStat Menus :


http://bjango.com/mac/istatmenus/

You also have some free alternative on the web

The Activity Monitor


http://www.tekrevue.com/tip/use-activity-monitor-energy-tab-os-x-mavericks/

And if you want to know the kW energy consumption, ArchonOSX is right.