Yes, but not as much as you think. Even though the light gets dimmed, the electricity saved is not proportional. For example, if you dimmed a 75 watt incandescent lamp by 25 percent, you will still be using around 66 watt. This is because the lamp still uses a lot of energy to generate infrared heat. The bulb becomes less efficient. Personally, I am not a big fan of dimmers, and recommend them only where absolutely needed.