Halogen light bulbs...energy efficient?

[sketchED]

A friend told me that halogen light bulbs that have a transformer (12 volt) are much more energy efficient than incandescent ones. Is this true, if so than what would would be the real wattage of a those small halogen lights that consume 50 watts? Any ideas anyone?

[ZenOps]

http://en.wikipedia.org/wiki/Halogen_lamp

More efficient than a regular light bulb, yes. They also last quite a bit longer, and stay brighter for longer too.

[brunes]

http://en.wikipedia.org/wiki/Halogen_lamp

More efficient than a regular light bulb, yes. They also last quite a bit longer, and stay brighter for longer too.

I don't see anything in that article that says that, and frankly it is not true.

Halogen bulbs are nice and bright, sure, but they are almost as inefficient as incandescents. They give off a huge amount of heat, so much that halogen lams require heat sheilds to be CSA stamped. You get fingerprints on the bulb and it can explode when turned on, that's how hot they get.

Anything that gives off a lot of surplus heat is fundamentally inefficient, because that is energy that is not being used for useful work (other than to heat your house if it is winter). Note I am using the word 'work' in the physics sense.

Halogens have a small edge on incandescents pe rlumen output. They also last twice as long. BUt they are nowhere near as efficient or have the lifetime of a CFL. You can get the same amount of light output from a 300W Halogen bulb or two 23W CFL bulbs, so you do the math.

You can do some more reading here:

http://www.elflist.com/article10_halo.htm

[ZenOps]

Its the reason that they can run hotter that halogens are more efficient than incandescents.

The filament in a halogen is linear, usually in a thin tube. Incandescents are usually in a bulb, with a very large evacuated airspace around the sides of the bulb (necessary for adequate cooling) A 60 watt halogen will run more efficiently because its got a smaller, denser, and therefore hotter filament than a 60 watt incandesent.

Halogens last longer and burn brighter for longer because of the metal re-depositing ability, basically it "reheals" itself.

CFL's are fine if you want to measure lumens, however it is slightly overstated as they do flicker at whatever hz they flicker at nowadays (200hz or so) so its contstantly turning off and on. Although we as humans cannot tell the difference, its not technically a steady stream of light.

You can't buy a regular light bulb that puts out 2500 lumens when using 65 watts (which the newest commercially available halogens can do)

In comparison, a CFL will put out about 1700 lumens for a 26 watt bulb (usually the highest a single CFL will go to, due to space restrictions) So approximately 38 watts of CFL = 65 watts of good halogen light if you measure by lumens. Comparing a CFL to a standard bulb is more like 3 to 4x more efficient.

BUT also, as you start scaling into the >100 watt range, the halogen becomes exponentially more efficient, whereas a CFL's efficiency remains linear the higher the wattage. So if you need a lot of light, halogen is still the way to go.