I have just changed the hard drive to SSD (Crucial 500, 480GB), and found the power consumption is more than the spin disk. 

When it was idling, the calculated remaining time from 100% battery level is around 6 hours, however, it was 8 hours with the spin disk. The power dropped more quickly when I used the computer to browse the internet, which was lightly using the CPU. It only lasted 4 hours under light usage.

So the conclusion is that SSD causes the computer to drain battery more quickly.

Some say SSD causes more CPU usage, because it is super fast. I do not know. Or SSD really consumes more power than spin disk?