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Recently we've been shopping for light fixtures, and have noticed a dramatic increase in non-standard bulbs. CFLs in particular seem to be drifting away from the common threaded base, in favor of 2-post snap in bulbs.

I know there are efforts underway to remove incandescent bulbs from shelves, and I don't necessarily disagree with this. But I'm worried about having to find or keep on hand hundreds of different types of bulbs for my light fixtures rather than a consistent size and base.

So... Is the standard base becoming a thing of the past? Is a new standard clear on the horizon, yet? Should I try to stick with screw-base fixtures, or is diversity likely to be okay in the long run?

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The "2-post snap in" is actually the GU24 bayonet connector. –  dpollitt Nov 11 '13 at 4:01

4 Answers 4

up vote 22 down vote accepted

Many countries are banning the sale of incandescent bulbs over the next decade. Canada is planning on banning them in 2012 (not entirely sure if this is a done deal or not though), USA is banning them at different wattages starting in 2012 and ending in 2014.

The GU24 (two-pin) base is being introduced to force the transition, and prevent incandescent bulbs from being used in newer fixtures.

From this page:

What is a GU24 base and how is it related to CFLs?

  • The GU24 socket and base system is designed to replace the Edison socket and base in energy efficient lighting fixtures. The ENERGY STAR® Program Requirements for Residential Lighting Fixtures, Version 4.0 require that residential lighting fixtures cannot use the standard Edison screw base, even if they do not have a built-in ballast. The same requirement is included in California's Energy Efficiency Standards for Residential and Nonresidential Buildings, known as Title 24-2005. This requirement is designed to insure that fixtures that receive ENERGY STAR® qualification when using an energy-efficient self-ballasted CFL, or are qualified as energy-efficient under Title 24-2005 cannot be operated with an incandescent lamp. The GU24 socket was designed to be compatible with these energy efficiency regulations. The GU24 base has two dual-diameter pins; the smaller portion having a diameter of 3.4 mm (0.13 inches) while the larger portion has a diameter of 5 mm (0.2 inches). CFLs with a GU24 base are designed to be connected directly to the power line, so they are functionally equivalent to screw-base CFLs instead of normal pin-base CFLs. Unfortunately, ENERGY STAR® refers to CFLs with the GU24 base as self-ballasted pin base lamps, a designation that may lead to confusion with pin-base CFLs that do not have an integral ballast. Some manufacturers are also making modular ballasts with a GU24 base on one end and a socket for a normal pin-base CFL on the other. These modular ballasts can be used to adapt normal pin-base CFLs to fixtures that have the GU24 socket, thereby reducing the amount of material that must be thrown away when the lamp fails.

GU24 base

I would bet Edison will not disappear for quite a while though: there are hundreds of millions of fixtures, and it's not practical (or environmentally friendly) for everyone to go out and replace every fixture in the next few years. My guess (and I have no authority in the matter btw :)) is that it will be 2015-2020 before you start finding more GU24 base bulbs than Edison.

Also, you can get Edison to GU24 adapters, which means even if Edison bulbs themselves disappear, you can still use your existing fixtures.

Edison to GU24

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This is a travesty! What will happen to all the "How many x does it take to screw in a lightbulb jokes?" –  Steve Jackson Oct 27 '10 at 13:38
Wow, that was somehow more information that I thought I'd find on exactly what was confusing me! We did the entire house in CFLs, but now I may have to start collecting those adapters for future-proofing. Thank you! –  Scivitri Oct 27 '10 at 20:36
That's outrageous. I want to go buy a bunch of CFLs and throw them at whatever government office came up with this nonsense. I've been using CFLs for years and LEDs for a year -- but they still don't beat standard bulbs for many applications. –  duffbeer703 Oct 30 '10 at 22:21
The thought of banning a light bulb truly shows how pitiful this country has become. If CFLs, LEDs, etc. save money without having to make any sacrifices, people will naturally prefer to buy them over incandescents. How many people out there want to buy an Atari or NES right now? Hardly any. But the next xbox, PS, etc. console will sell like hotcakes. The government stepping in and making demands about what people can and can't buy, when market forces would've taken care of the issue without any intervention, is a great display of how they love to feel powerful. –  Michael Feb 1 '11 at 11:36
I must note that the outrage is a bit premature. There's nothing in the above answer's reference that says that the Edison base cannot be used EVER. It's just that the EPA will not grant an Energy Star label to any device that has an Edison socket, and can thus accept an incandescent. So, once this goes into effect, if the fixture is Energy Star rated, it pretty much guarantees high energy efficiency compared to non-energy-star-rated fixtures, because you won't be able to put anything BUT an energy-saving bulb in. For the Edison base to be BANNED, an Energy Star rating must be mandated. –  KeithS Sep 30 '11 at 16:19

This page on Lightbulbs Direct has information about the various types of fitting.

There are two main type - bayonet and screw.

Each of these has sub types, two for the bayonet, four for the screw cap.

In the UK it used to be pretty much exclusively the wider bayonet fitting that was used, with the occasional screw fitting just to confuse you. Other countries would have different fittings.

I think that with increased globalisation of manufacture and sales - which country doesn't have an Ikea! - we are seeing appliances and light fixtures from around the world being sold everywhere so there has been an apparent proliferation of fittings.

Just buy the bulbs you need for the fixtures you have.

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Very informative link; I could wish they had a chart of bulb designation to pictures on store light-bulb isles. Most of those fittings I'm familiar with, and tend to be purpose-specific. But I've started seeing different bases in, say, standard size flushmount fixtures. The GU24 bulb prompted my question, which is a bulb I'd have to special order. And isn't on the page you linked although they look to be mentioned at the very bottom under CFLs. It looks like CFLs will be a much more diverse bulb type. –  Scivitri Oct 26 '10 at 18:12
Interesting that bayonet fittings are common in the UK. I have never seen them, except in cars. –  Vebjorn Ljosa Oct 26 '10 at 18:30
Bayonet used to be the standard in Australia as well but over the last 30 or 40 years ES has gradually become more common (probably due to imported light fittings) to the point where today it's about half and half. –  John Gardeniers Oct 26 '10 at 20:51

Until low-cost LED lighting is available, I'm afraid incandescent lighting is going to be a mainstay in my house.

I tried the compact fluorescent, bulbs. I really wanted them to win out, but frankly I didn't get the promised benefits for the extra cost. They burn out just as quickly if not more so than the incandescent bulbs in my experience. Also, the one major thing is that they are 99% guaranteed to break if you drop them, while their progenitors will bounce at least 75% of the time unless you drop them from a great height. I've broken so many of those stupid coiled fluorescent bulbs it just isn't funny.

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A) You either had a small sample or bad luck. I've been buying CFLs for ten years now as I moved into bigger and better places and some bulbs are still with me after that whole time, while less than a quarter of what I've bought have burned out since then. –  Sparr Oct 27 '10 at 4:04
I went through about 25 bulbs. Very few of them lasted more than a year. I suspect, though, that they may be more sensitive to power surges. I live in a rural area where the power is a bit iffy sometimes. –  JohnFx Oct 27 '10 at 14:48
At home I've had great success with CFLs lasting forever compared to incandescents. Even in the worst locations (small spaces/no airflow, outdoors, and in places with lots of cycling). At work, it's another matter. We gave up on CFLs because we were replacing them monthly due to failures. All our other electronic equipment is fine though. Dunno. Something out there can kill CFLs real fast, hope somebody figures out exactly what it is so we can solve the problem! –  Brian Knoblauch Oct 27 '10 at 14:56
JohnFx: installing a whole-house surge protector may help. It could also be the brand of lights, they're not all created equally. Like you, I too, am waiting for lower-cost LEDs, but also more importantly, dimmable LEDs that actually work well. Many of my lights are dimmable, and frankly, dimmable CFLs are not that great. –  gregmac Oct 27 '10 at 14:57
If you don't leave them on at least 15 minutes, they can die much faster than they should. –  Peter Oct 28 '10 at 18:06

I don't know about elsewhere but Australia is phasing out incandescent lighting - by law. Of course like so many other bits of legislation it was never thought through properly and many people have to replace light fittings because CFLs are larger than their incandescent equivalents and simply won't fit into the existing fittings. :(

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