The Apple Thunderbolt Display Reviewby Anand Lal Shimpi on September 23, 2011 2:56 AM EST
Unsurprisingly, power consumption hasn't changed much in the past year. The Thunderbolt Display draws a bit less at its dimmest setting (likely just panel efficiency variance) and draws a bit more at max brightness:
While powering a 15-inch MacBook Pro and reading data from an attached Pegasus R6 (copying to a local SSD at around 200MB/s) I measured total power consumption for the display (max brightness) at 179.6W. That number could go up if the battery in the MBP was near empty and thus being charged at a higher rate.