Light fittings are one of the few electrical devices in our houses with just two functions, just on and off. Dimmers can be installed to adjust the settings and brightness of light fittings allowing you to not only control the brightness of a room but also adjust the amount of expelled energy by controlling the emitted voltage supplied to the fitting.  They are able to be fitted onto incandescent, halogen and compact fluorescent lighting so cover the most common lighting in the house. The applicable savings are quite relative as dimming your lights even 20% saves nearly 20% in energy. Dimmers can cost anywhere from $5 to $50 but the majority of installation cost will come from the electricians bill.