# How efficient can halogens light bulbs be?

**URL:** <https://boards.straightdope.com/t/how-efficient-can-halogens-light-bulbs-be/635418>\
**Category:** Factual Questions\
**Created:** [September 21, 2012, 6:36pm UTC](https://boards.straightdope.com/t/how-efficient-can-halogens-light-bulbs-be/635418 "2012-09-21T18:36:57Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\
**Post date:** [January 16, 2013, 2:51pm UTC](https://boards.straightdope.com/t/how-efficient-can-halogens-light-bulbs-be/635418/21 "2013-01-16T14:51:27Z")

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> [@Mdcastleman](#):
>
> One of my halogens (43 watt GE brand) that I run on 1/5 brightness all night just got dimmer and dimmer till it was about half brightness all the way on, and then burned out. I busted the outer globe open and the capsule was noticiably blackened. I am trying alternative to regular bulbs, but I’m just underwhelmed at every turn.
> 
> Also of note, Home Depot always seems to have them, but Target and Walmart are always out of stock, I’ve checked six times.

Running halogens at reduced brightness is bad for them because the halogen cycle requires that the lamp be hot enough ([at least 70-80% of full power](http://www.teklight.com/faq_s.html), third question down, also see the next one about dimmers and bulb blackening/failure) so that evaporated tungsten doesn’t get deposited onto the bulb, which explains the darkening and early failure.

That is to say, you need a separate low-power light if you want a night-light (it is also more efficient to have a small lamp at 100% brightness than a big one at 20%, plus the color temperature is higher, unless you specifically want the orange glow). For example, [one of these lights](http://en.wikipedia.org/wiki/File:Nightlight.JPG), with a built-in light sensor that automatically turns it on when it gets dark. Also, the small 5-7 watt bulbs these lights use are exempt from the [phase-out](http://en.wikipedia.org/wiki/Phase-out_of_incandescent_light_bulbs#Federal_legislation):

> [@](#):
>
> The efficiency standards will start with 100-watt bulbs and end with 40-watt bulbs. The timeline for these standards was to start in January 2012, but on December 16, 2011, the U.S. House passed the final 2012 budget legislation, which effectively delayed the implementation until October 2012.
> 
> Light bulbs outside of this range are exempt from the restrictions. Also exempt are several classes of specialty lights, including appliance lamps, rough service bulbs, 3-way, colored lamps, stage lighting, and plant lights.

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**Author:** ![Mdcastle](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mdcastle](https://boards.straightdope.com/u/Mdcastle)\
**Post date:** [February 18, 2013, 5:15pm UTC](https://boards.straightdope.com/t/how-efficient-can-halogens-light-bulbs-be/635418/22 "2013-02-18T17:15:49Z")

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Also of note, you used to be able to buy 240 watt halogens that would give the same light of a 300 watt halogen. They were more expensive and didn’t seem to last as long in my halogen torchiere lamps so I quit using them. Now I can’t even find them online at the bulb places.

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