Lower FPS to conserve battery life in iPhone opengl-ES application?

I'm wondering about providing an user selected option to lower the framerate in my opengl based game to conserve battery life, and in general detect parts of the game where no movement occurs and lower the framerate there as well (when saying framerate I actually mean the number of times per second the entire screen is redrawn using opengl commands)

The opengl app is made pretty much the same way as the opengl templat开发者_StackOverflow社区e that comes with xcode.

Did anyone check if this has any significant impact on battery life?

Sure framerate have impact on battery life. It need cpu/gpu cycles to render each frame. But how much impact on battery life depends on what are you rendering. Btw, you might want to give users ability to dimmer the backlight as well (that have impact too, huge).