How we light up the places where we live and work makes a big impact on how we feel. It also makes a big impact on the environment. The kind of bulbs, the kind of fixtures, the kind of power, and the habits we keep can all add up to a very significant greening. Start with the fact that a conventional incandescent bulb turns only around five to ten percent of its consumed energy into light, the rest goes out as heat. From there, there's no limit to how green your lighting can be.