But no matter what the resolution is, a major way to save on battery life is not to have the display running when you don't need it.
For a MacBook, open up the Energy Saver window and adjust the position of the slider control at the bottom marked Turn Display Off After. You can vary the time before the screen shuts down from "never" to as little as one minute.
Apple's Energy Saver window lets you adjust when to turn your display off.
I also dim the screen a bit when on battery power by hitting the F1 button several times until I get to a brightness that is comfortable but not too bright. (If you dialed down too far, the F2 button makes the screen brighter.)
Windows lets you set your power plan for turning off the display and putting the computer to sleep.
With a Windows system, go to the Power Options page and edit the power plan to suit how you work and play. When I'm running the system on battery, I generally set the screen brightness to roughly 80% and have the screen turn off after 15 minutes of inactivity.
Many current Windows laptops also use function keys to make it easier to dim or brighten the screen.
5. Put it to sleep
While you're tweaking your power plan settings, go ahead and set a period of inactivity after which your computer will go to sleep.
How long you wait before putting your system to sleep can affect battery life profoundly. The best approach is to use trial and error to find a balance between battery life and convenience -- for example, my own settings put the computer to sleep after 45 minutes of inactivity. Your mileage may vary.
In a Windows system, go to the Control Panel, click on the Power section and select Change plan setting. Here, you can adjust how long a system will wait before it goes to sleep.
For even more efficiency, EnviProt's Auto Shutdown Manager, a $15 Windows utility, models how you use your computer and can intelligently put the system to sleep and wake it up. It even tabulates how much power has been saved and the amount of carbon dioxide you've kept out of the atmosphere. You can try it for free for 45 days.
And you don't have to wait for the automatic triggers to kick in. Go ahead and manually put the system to sleep if the computer is sitting idle with nothing going on -- by doing this, you can save as much as 15 watts. (Most Windows systems let you press a function key to put the computer to sleep; which one you use depends on your specific system.)
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