In an interesting test by the folks over at Tom's Hardware, solid-state drives (SSDs) suck more power than their platter-based counterparts. Why should you care? Because the MacBook Air features an SSD in its higher-end configurations.
Tom's looked at four different SSD models, and compared them with a 7,200 RPM disk of the same size. One disk, from Crucial, touted its "low power consumption" in marketing materials. However, the disk reduced its test laptop's battery runtime from seven hours to six hours. Ouch.
SSDs are significantly faster, of course, but the idea that they consume less power appears to be false. As manufacturers develop thinner and thinner sub-notebooks, power consumption can only become more and more important.
Update: Many commenters are pointing out problems with how Tom's Hardware conducted the test. Peter cites a comment from our sister blog Engadget that says "The TH article was, as usual, significantly flawed. The benchmark they used to test battery life restarts itself after each completion, doing so until the battery is dead. However, the article did not report how many times the benchmark was able to run on the SSD vs. the mechanical HD." Commenter Greg recommended this Anandtech article as a counterpoint to this one.