The Construct 2 engine is well-optimised. A sprite with a single animation with a single frame (or an animation speed of 0) that does not move does no work other than copying its cached co-ordinates every frame. That involves a negligible amount of CPU work.
If the object has more than one animation or more than one frame and the animation speed is above 0, the engine will process it every tick to run the animation. This also involves a probably negligible amount of work (it's very simple logic), but if you're talking about vast numbers of sprites, it might be something to be aware of. Note also if you change the animation speed so it's not 0 any more, the engine will start ticking it. (The animation speed 0 thing is intended so that tile based games using lots of animations and frames for static tiles which do not animate are still handled efficiently.)
If you move the object, it will keep re-calculating the vertex co-ordinates. This is also probably a negligible amount of work (it's highly optimised since movement is frequent).
So sprites which don't move or animate are blazingly fast. You probably don't need to worry about it.