Are energy saving and LED light bulbs dimmable?

No they are not.  Whether or not a light bulb can be dimmed will depend on its design and for energy saving or LED bulbs you will need to check the manufacturer specifications to see if they are dimmable or not.  Attempting to use one of these bulbs when they are not dimmable with a dimmer switch can cause the bulbs to fail or even damage the fixture they are going into.

Compact Fluorescent Lamps (CFLs) and their Dimmability

Dimmable CFL lamps will be labeled as such on the packaging.  If dimming is not mentioned you should assume that it is not dimmable.  They will often require a specific type of dimmer switch such as an electronic or a low voltage one.  If the dimmer switch you have worked with an incandescent bulb this does not mean it will automatically work with a CFL lamp.    It is worth noting that dimmable CFLs will normally only have a limited dimming range (which should be advised in the specifications) and there be a slight delay or flicker in the lamp when it is adjusted.

Light Emitting Diodes (LEDs) and their Dimmability

LED technology offers wider dimming range then dimmable CFLs but you will still need to check if the bulb is dimmable before purchase.  Again, if dimming is not mentioned you should assume that the bulb is not dimmable.  You will also need to make sure that the LED bulb is compatible with your dimmer switch as well.  You should be able to find this information under the manufacturer specifications.  LED bulbs can dim to be as low as 1% of their brightness level at full and should not flicker when dimmed. With an LED bulb you will need to check that the driver within the fitting is compatible as well.  This will only be applicable if your bulb is not 230-240v.

A brief guide on how to check your bulbs are dimmable:

1. Check the Bulb Packaging: Always purchase bulbs that are explicitly labelled as "Dimmable."
2. Check the Dimmer Switch: Check your dimmer switch to make sure the new bulb is compatible.  You will likely need to change to a new dimmer switch and choose one that is specifically rated for LED or CFL lamps.  You can refer to the manufacturer specifications for the bulb or the dimmer switch if you are unsure.
3. Check Minimum Load: This applies more so to LED bulbs; make sure that the total wattage of the installed LED bulbs meets the minimum load requirement of the new LED dimmer switch and driver.
4. Test and Verify: We would suggest that you buy one dimmable bulb and one compatible dimmer at first to test it before you commit to replacing all of the bulbs in your home to LED or CFL lamps.