DeepSleep hibernates your Mac to save power

Editor’s note: The following review is part of Macworld’s GemFest 2012 series. Every weekday from mid June through late August, the Macworld staff will use the Mac Gems blog to briefly cover a favorite free or low-cost program.

My MacBook Pro just celebrated its third birthday, and though it’s still going strong, I’ve been taking precautions to make sure it keeps performing at its best. One thing I’ve been trying to improve is battery life, and DeepSleep has greatly helped with that. This app does only one thing—it puts your Mac into Hibernation mode instead of standard Sleep mode—but it does it well.

Usually, when I’m finished using my MacBook, I just close the lid to put it to sleep, which conveniently leaves all of my open applications running. When the lid is opened again, my MacBook wakes up quickly and I can pick up where I left off. While there’s nothing wrong with using a MacBook this way (actually, I’m sure a lot of us do this), the laptop’s battery still drains while asleep if the laptop isn’t connected to AC power.

But OS X also supports a special Hibernation mode. When in Hibernation mode, your MacBook doesn’t use any power while asleep, and your open applications and files are still there when you wake the laptop. How? When you put the laptop to sleep in Hibernation mode, OS X writes the contents of the computer’s RAM to the internal drive. Since the RAM doesn’t have to retain that data during sleep, it doesn’t need to draw power. When you wake the computer, OS X copies the data from your drive back to RAM. The downside to Hibernation mode is that it takes longer for the computer to go to sleep and to wake from sleep because of the RAM contents being written to and read from your drive.

You can use Terminal commands to force your Mac to use Hibernation mode instead of standard sleep mode, but then you’re stuck with Hibernation mode every time you put your Mac to sleep. If you’re just going to grab some coffee, the slower sleep and wake processes can be a hassle—you likely want Hibernation mode only when leaving your Mac for longer periods. With DeepSleep installed, you can use Hibernation mode on demand: You just launch DeepSleep (or use its accompanying Dashboard widget) each time you want to put your Mac into Hibernation mode. A pop-up notification asks if you’d like to continue; assuming so, you click Hibernate.

To wake your MacBook, you just open the lid and press the Power button. As noted above, it takes a little while longer to wake from Hibernation mode than from regular sleep, but you’ll still find your machine looking just the way you left it.

(You could get a similar result—and similar energy savings—by using OS X’s System Resume On Restart feature and shutting your Mac down when you’re not using it, but that’s considerably slower. Whenever you want to use your Mac, you must power it on, wait for startup to finish, and then wait for the Resume feature to relaunch all your apps.)

It’s worth noting that DeepSleep isn’t just for MacBook users: Desktop-Mac users can use the utility to reduce energy bills, as your desktop Mac similarly doesn’t use as much power when hibernating as when sleeping.

DeepSleep probably won’t dazzle you, but this no-frills tool provides an excellent way to save power in between uses.