Although there are literally hundreds of light fittings in existence, your home probably only has a couple- the image above are some common ones.

You really don’t want to mess it up, so first step is scribble down the fittings you need before you start shopping for bulbs. Not only will they fit, they’ll be the right voltage too.

In most cases the unit bases are not interchangeable, however, you can buy a base convector if need be.

  • B22 – Popular large “Bayonet” –  push-and-twist, 22mm in diameter- found in many ceiling fittings in the UK
  • E27 – Edison Screw ( ES ) , 27mm in diameter – widely used in ceiling, table, wall and floor lamps.
  • E14 – Small Edison Screw ( SES ), 14 mm in diameter – many uses including  table, wall and lamps.
  • GU10 –  Bi-pins (10mm apart) twist-and-lock fitting found on 240V spotlights – Be careful not to confuse this with the low-voltage (12V) MR16 push-fit spotlight fitting
  • MR16 – This is a bi-pin push-fit spot lamp used in 12V low-voltage spotlights circuits – that includes a transformer and possibly a dimmer.  There are some possible difficulties in replacing existing MR16 lamps. As older technology transformers (240V to 12V) and dimmer switches have to be taken into consideration. Transformers and/or dimmers switches may need to be replaced with LED compatible versions.  An alternative in to replace the  MR16 lamp holder with a GU10 (240V) lamp holder and remove  the transformer and use GU10 lamps. Any changes to your circuit should be carried out by a qualified electrician.
  • G9  These are also called capsules. These small lamps have two looped pins and run on 240V. G9 are found in light fittings and spot lamps.

‘B’ is for Bayonett, you can thank the British Empire for that.  ‘E’ is for Edison Screw, dominant in the US, and I’m sure you know who Thomas is. And ‘GU’….I actually don’t know what that is. The good news, however, you don’t need to know what they mean either.