Sprite Atlases take twice the size in memory in OpenGL ES 2. A 1024x1024 texture, 32 bit takes 4 mb in ram when used as a normal texture. The same texture, packed with the sprite packer uses 8mb memory. The atlas size is 1024x1024, rgba32, so it should be the same.. the same thing also happens with 16 bit textures, so it doesn't seem to depend on the texture format.