Dimmable CFL bulbs

Why would I use dimmable CFL bulbs? Surely I can just use a normal CFL bulb in a dimmable fitting?

Unfortunately it’s not quite as straight forward as you may think. You need to remember that a CFL or compact fluorescent lamp is actually, just as the name suggests, a small fluorescent tube which has had its glass tube twisted into the size and shape of a traditional light bulb with its starter (or ballast) moulded into the housing.

This is further complicated by the fact that most CFL bulbs are not designed to work with traditional dimmer switches. So you'll need to make sure your dimmable CFL bulbs are compatible with your traditional dimmer switches before buying them.

If buying online, this information should be easily available and if it isn’t, email the seller and ask them.

dimmable cfl bulbs

Older style CFL bulbs used magnetic based ballasts located in the base of the bulb and this is what starts the bulb and keeps it lit. These were not suitable for use with dimmer switches as they flickered quite badly and could overheat, causing a potential fire risk.

Thankfully most modern CFL’s now use electronic ballasts which are a huge improvement, but still not perfect. While many of them are now compatible with dimmers, not all of them are. So you should always check with the supplier before buying.

What if you use standard CFL bulbs with a dimmer switch?

Using a non-dimmable CFL bulb with a traditional dimmer switch will likely shorten the life of the bulb and will definitely invalidate your warranty. It may dim for a while but the ballast in the CFL will likely overheat.

A few years ago, you would definitely have had to change your dimmer switch to work in conjunction with a dimmable CFL bulb. Now, provided you are careful and make sure the bulb you are buying is capable of working with a traditional dimmer switch you should have no problems. If however you are using old dimmable CFL’s that you have had in the cupboard for a few years, they may not be compatible.

The easiest route is to buy new dimmable bulbs and make sure they are compatible with your dimmer. Alternatively you can buy dimmable compact fluorescent bulbs that will work with a traditional light switch. By turning the light switch on and off quickly a few times, the bulb will adjust its brightness and you simply stop when you reach the desired brightness level required.


The biggest downside of dimmable CFL’s is that they are more expensive than non-dimming CFL bulbs. They can be around twice the price of normal non-dimmable CFL bulbs.

If you don’t buy carefully you may also have to replace your dimmer switches which will be expensive (if your'e in this position, it's easier and cheaper just to return the bulb and buy a compatible one).

They can flicker as the power input is varied until the arc within the bulb stabilizes. If the bulb flickers you need to turn the dimmer switch up a little until it stabilizes and stops flickering.

If allowed to continually flicker the bulb will ultimately fail as this flickering is just like turning the bulb on and off repeatedly.

Alternatives to a dimmable CFL bulb:

A lot of the time we have dimmer switches in rooms where we have a lot of low voltage GU10 down lighters purely because if they were all on at full power the room would be too bright.

An alternative would be to change the dimmer switch for a regular switch and use lower wattage CFL bulbs instead. They're a lot cheaper than the dimmable CFL’s and with a lower light output you won’t need to be able to dim them.

Cold cathode fluorescent light bulbs:

As with all technologies, development never stops and the latest incarnation emerging from the low energy light bulb world takes the form of Cold Cathode Fluorescent Light Bulbs (CCFL). These have a longer lifespan than normal CFL bulbs as they operate at lower temperatures, they can be dimmed using traditional dimmer switches and contain less Mercury than CFL bulbs and they light up instantly.

On the down side they’re currently only around half as bright the equivalent standard CFL bulb.

The technology involved in manufacturing dimmable CFL bulbs has and continues to move at a fast rate with the electronic ballasts improving all the time. So while you can buy dimmable CFL bulbs quite easily online you should always check:

  1. They are compatible with your current dimmer switch. Many modern dimmable CFL’s will work from a standard dimmer.

  2. You have all the same type and brand of bulbs fitted in your room, as different bulbs can light at different levels making the light in the room uneven.

For more information on whether or not you should be installing CFL light bulbs read my article on the advantages and disadvantages of CFL bulbs.

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