If you have many incandescent lights in your home, you could be paying for it as they convert around 10% of the energy they consume for lighting. Essentially, this means that the remaining 90% is just used for heat. As we spend around 10% of our budget on lighting, this is significant.
Nowadays, there is huge investments in lighting so you will find options like compact fluorescent lamps (CFLs) and light-emitting diodes (LEDs) which will reduce your energy usage on lighting by up to 75%. Furthermore, there are also options for controls so that lights aren't on when nobody is there to see the benefit. Compared to traditional incandescent bulbs, CFLs are known to last up to ten times longer. What’s more, LEDs consume even less energy and can last even longer than CFLs. Finally, LEDs contain no mercury while CFLs do.