For now, the laptop manufacturers that have offered Blu-ray drives have also avoided revealing the precise effects of Blu-ray playback on battery life. That's probably for a very good reason, as some claim battery life can top out at one hour in some cases.
"The laser that runs the show [in Blu-ray players] is a very high-power laser," notes Mercury Research analyst Dean McCarron. That laser is one of the main things that conspire to raise power consumption.
The other part of the equation has to do with the process of decoding data from a Blu-ray disc and turning it into moving images on your screen. When Blu-ray was first introduced, this process was all done in software, which is very taxing on the CPU, eating up processing cycles and power.
As the drives become more common, improvements are likely to be made in video cards and CPUs to process the Blu-ray information more economically, power-wise; but for now, a Blu-ray equipped laptop should be considered a laptop-with-a-wire-next-to-an-outlet.