3/15    According to ABC, 90% of the energy used by incandescent bulb is
        wasted in heat.  That mean only 10% of the enery it takes in
        outputs useful light. In addition compact flourescent light takes
        about 1/4 of the same energy for the same output. So let's suppose
        I have a 25W compact flourescent bulb and outputs as much as a
        100W incandescent bulb (or 10W of useful light). Can I safely
        assume the compact flourescent bulb also outputs 10W of useful
        light and 15W wasted in heat, or 10/25 (40%) efficiency?
        \_ I'm sure that will make a major diff. in 'saving the planet'
           Of course it won't. The only real way is population control.
           \_ 36 years old and no kids yet.  Can I have a tax break?
        \_ of course in winter, the 'heat' isn't wasted.
           \_ Yeah.  But in summer, not only is the heat wasted, it makes your
              AC work harder which takes even more energy.
           \_ not entirely -- except when you consider the energey used to
              generate that electricity in the first place.  Usually generated
              by some form of heat engine, again usually burning fossill fuels.
              So that 90W of electrically-created heat required the waste of
              another ~200W of heat at the power plant.  Compare this to
              burning gas locally to generate heat, where virtually all the
              heat in the gas goes to heating.
              \_ totally agree. But neither heat nor power generation is
                 factored into light bulb efficiency anyways -pp
           \_ Yeah.  But household furnace usually burns natural gas.
              Burning gas to generate heat is more efficient than burning gas
              to generate electricity and then using electricity to generate
              heat, which in turn is cleaner than burning coal to generate
              electricity and then using electricity to generate heat.  Also,
              in summer, not only is the heat wasted, it also makes your AC
              work harder which uses even more electricity.  That's the same
              reason why, if you leave your PC and monitor idling at, say, 20W
              in an air-conditioned room, you're actually wasting more than
              20W.
              in an air-conditioned room, you're actually using more than 20W.