Do Dimmable LED on Standard Dimmers Save Energy?
Yes, dimmers reduce energy consumption of dimmable LEDs. Unlike incandescent bulbs, the electricity used is fairly linear with the light output; at 50% brightness it should use roughly 50% of the power. 

Generally speaking, dimming will allow the bulbs to run cooler and extend their life spans. There may be some exceptions for some particular bulbs with particular kinds of dimmers, however, LEDs advertised as "dimmable" should not have any problems.