There are two types of screens I’m going to talk about: backlit and OLED (organic light emitting diode). The power savings settings are different for each.

On OLED screens, each pixel is powered individually. So to save power, you want a black wallpaper or darker wallpapers. Less pixels to light, less power used.

On LCD/backlit LED, the whole screen is dimmed and brightened based on your settings, but to block out the backlight, a pixel has to be turned ON to block the backlight which means on this type of screen black draws more power.

On both, turning down the brightness will save power.

It appears on my Galaxy Nexus to have increased my battery life because the screen is no longer the top power user under Settings, then Battery.

To found out what screen you have, use Google to research it.

It can be made more confusing because some phones, like the Nexus One, used both. 🙂 Good luck! Worst case, try both ways then take a look under settings to see what is using more battery power over time.

When you want to save some money, check out http://circlephone.com and then you can afford an extended battery. 🙂