Low Energy Light Bulbs

Low energy light bulbs are a quick, easy, low cost and effective way of saving energy and reducing your electricity bills.  In homes, lighting typically accounts for 15-20% of electricity bills.    A fairly typical house with only traditional incandescent and/or halogen bulbs could cost around £100 per year to light, but the householders would only receive around £9s worth of actual light. The incandescent bulbs give off the other £91s worth as heat.  Please note that Halogen bulbs sold as ‘low voltage’ (i.e. MR16 types) are not low energy!

We recommend fitting low energy light bulbs in all your light fittings.  Unfortunately there is no funding available through the Green Deal or ECO for low energy lighting for homes.

There are two main types of low energy bulb:

  1. the familiar compact fluorescent light bulbs (CFLs)
    2. light emitting diode bulbs (or LEDs).

The £100 cost illustration given above could be reduced to £20 if only CFLs are used, and to as little as £10 if only LEDs are used.


The CFLs available now are much improved compared to those available 10-15 years ago. Warm-up times are shorter, flicker is much reduced, there is a wider range of colours and almost all bulb shapes and fitting types are available, as are dimmable bulbs.


LED bulbs have no warm-up time, no flicker and the most efficient ones use half the electricity that CFL bulbs use. They can also last over 10,000 hours. However they typically cost £10 or more at the moment, so will only pay back in a reasonable time if used in fittings with a high usage.  An LED bulb will give the equivalent of about 8 to 10 times its stated wattage, so a 40w halogen would need a 4w or 5w LED to give a similar light level.

Investment: 20p – £10 per bulb (CFLs) / £10 – £30 (LEDs)
Financial Saving: Up to £80 per bulb over its lifetime
Carbon Dioxide Saving: Up to 400kg per bulb over its lifetime

Standard CFLs can be found in most local retailers. More unusual CFLs and LED are available from good hardware stores and specialist retailers.

Replacing Halogen spotlight bulbs

Halogen bulbs commonly come in two common types in domestic homes.  You need to know which you have to know how best to replace them. You can easily tell by examining the pins and comparing to the pictures

240V GU10 fitting (left) and
12V GU5.3 (MR16) fitting (right)

240V bulbs have blunt terminals and twist in like a bayonet bulb. “GU10” refers to the style of pins that slot into a bayonet style fitting.

12V bulbs have pointed terminals that push straight in to the fitting. “MR16” (also known as a GU5.3) refers to the style of reflector, called a “Multifaceted reflector” and the 16 refers to the diameter in eights of an inch, i.e. 2”.

CFL replacements

Both sorts can be replaced by CFL versions (similar technology to the “stick” bulbs). However, most of these CFL bulbs are slightly longer than the existing halogen bulbs and may not fit in some fittings. However, if they do fit, they are the most cost beneficial to use. They will typically be 9W or 11W to replace a 50W halogen.  You can replace halogen bulbs with CFL equivalent bulbs as long as they fit satisfactorily in the fitting.

240V GU10 CFL

LED replacements

Alternatively you can replace the bulbs with LED bulbs. These are generally the same size as the original halogen bulb, they save more energy but are more expensive than the CFL version.

LED 240V GU10 bulb with a cluster of small LEDs

LED bulbs can be put direct into any 240V GU10 fitting. They are more expensive than CFL bulbs but are the same size and shape as the original halogens. LED bulbs have a very long lifetime.

12V “MR16” LED with three large LEDs

12V bulbs need a transformer to convert from the mains at 240V.

The transformer normally installed with 12V   halogen bulbs is not normally suitable for driving LED bulbs. The lower current would cause the transformer to deliver a voltage that is too high for the bulb and reduce its life.  If you have several bulbs being driven from one transformer, you can replace all but   one, and leave one halogen in place to keep the voltage in the correct range, otherwise you need to replace the transformer. The transformer is quite cheap   (~£5) but would need to be professionally installed.


(nb: this information may need updating.  Feedback is welcome)

  • ‘Precious Earth’ in Knighton (01547 528080)
  • ‘Bunners’ in Montgomery (01686 668308)
  • Wholesale Direct in Shrewsbury (01743 462020)
  • City Electrical Factors, Sh’bury (01743 462576)
  • Edmundson Electrical, Sh’bury (01743 441464)
  • Clee Hill Electrics in Church Stretton (01584 872003)
  • City Electrics in Catherine Street, Hereford
  • Larger DIY stores
  • Efficient Light – or ring 08702 425384. They offer a 10% discount on phone orders only if you use the code ‘HES’, and free delivery for orders over £25
  •,  good for LEDs
  • Screwfix ( are particularly good if you want to buy 5 of the same bulb
  • (lots of useful advice).

Extra Information

  • Check the wattage of outside lights, which can be high energy users. If possible replace these with solar lights available from DIY stores or from
  • Remember to switch lights off when not using them, even low energy ones. •
  • Low Energy Bulbs should be fitted straight away (not left until the old bulb goes). Inefficient bulbs should only be kept for emergencies or for where they are seldom used.