Whats wrong with Halogen

My friend Mahesh is taking his time moving into a new house.  Early in 2011, he left a halogen lamp on all month and his electric bill spiked (probably by about $20).  I told him to get rid of it and in email with him and some other family members and the question came up

          "Whats wrong with Halogen (if its low voltage)?" 

Here's what I wrote back ...

From what I've read, incandescent bulbs filled with halogen gas are at best only about 30% more efficient (lumens per watt) than traditional tungsten-based incandescents (not sure what gas is in there).  These halogen-filled bulbs is what folks who didn't want CFLs or LEDs were going to get before Congress decided they should try to kill the light bulb efficiency standards they (or, more likely, a different Congress) passed a while back.  In contrast, CFLs and LEDs are 300-400% more efficient than traditional bulbs.  Halogen is the 15 mpg SUV of the lighting world.  It's better than the 13 mpg SUV, but it's still an SUV. :)

I note that we wouldn't need these standards as much if energy was priced to include more externalities.  Then the market could do the work instead.  But Congress is scared of carbon pricing. :P

As you well know, the voltage at which electricity is delivered does not change the amount of work it is able to do, as long as there are enough amps.  Just think about the 90W Intel processors drawing 80 amps because they run at 1.1v (or less).  Thus low-voltage halogens are just as hot

(and thus wasteful) ... they simply burn through more electrons with less potential energy (voltage) per electron.

[need to explain this better for non-EEs :]

Anything consuming electricity that is hot to the touch is wasting a lot of energy as heat.  Even an electric heater is usually wasting a lot of energy back at the power plant (2/3rds of the energy at a thermal plant) and a decent bit on its way to your house (~10%).

For more information, see Lighting.