OpenGL-ES Puzzle game - making drawing battery efficient?

I've got an iPhone game that is basically finished, but I have been spending some time profiling as I want to get the power usage down as low as possible, but I'm a开发者_运维百科n OpenGL ES noob so I'm looking for some pointers.

The game is a fairly simple puzzle game, so 90% of the time the board is redrawing for no reason. At the moment I have a 'dirty' flag and only render anything if it is set, but then I draw everything, when most of the time only a tiny part of board needs updating (ie the timer, or one of the pieces).

Is there a common strategy to use with OpenGL for only updating parts of the screen, or does it assume that you want to redraw everything, all of the time?

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Your application should wait until something in the scene changes before rendering a new frame. Core Animation caches the last image presented to the user and continues to display it until a new frame is presented.So you don't need to draw every time , just check for the update, and draw only when there is any update. EDIT: For more details check opengl es programming guide- here's [a link]http://developer.apple.com/library/ios/#documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/Performance/Performance.html