We sometimes sneer at cellphones equipped with Adobe's Flash browser plug-in: On tiny, energy-efficient mobile processors, the plug-in spikes CPU-usage, causing a big drain on battery life and often making the poor host browser so stuttery and unresponsive that it is rendered useless. But what of full-sized computers? They can handle it, right?

Maybe not. Much has been made of Apple's decision to ship the new MacBook Airs without the Adobe plug-in, and in future all Macs will be made this way. In tests run by Wired.com's sister site, Ars Technica, it turns out that having Flash installed can cut the notebooks' battery life by one third. That's right. Simply by not having a browser plug-in installed, the 11-inch MacBook Air gets two extra hours of battery life. Ars:

Having Flash installed can cut battery runtime considerably – as much as 33 percent in our testing. With a handful of websites loaded in Safari, Flash-based ads kept the CPU running far more than seemed necessary, and the best time I recorded with Flash installed was just 4 hours. After deleting Flash, however, the MacBook Air ran for 6:02 – with the exact same set of websites reloaded in Safari, and with static ads replacing the CPU-sucking Flash versions.

Anecdotal reports of the new Airs say that they run cooler and quieter than other Mac notebooks, unless they are using Flash. YouTube videos and Flash ads are pretty much the only things that cause the machines to heat up, and for their usually silent fans to spin up.

What to do? Well, there are lots of great Flash-blocking plug-ins for browsers, but these are rather heavy-handed. The sites you visit still think you have Flash, and serve ads and video only for them to be suppressed. If you uninstall Flash completely, though, the site will often have a fallback, serving static ads and – in many cases – plain HTML5 video. The content creators get their ad impressions, you get less blinking crap and better battery life, and the world gets the hint that maybe Flash isn't as ubiquitous as it used to be.

The future of notebooks: Ars reviews the 11" MacBook Air [Ars via Steven Frank]

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