Tuesday, 19 July 2011

Should I replace my existing light bulbs with LEDs?

Those of you who have installed solar panels will be aware that whilst they are justified in environmental terms, without the government introducing the FIT, “Feed in tariff” they’re economically doubtful

I suspect exactly the same argument could be applied to replacing your existing “cheap as chips” energy wasting light bulbs. Unfortunately, because the last Labour government introduced legislation phasing out existing incandescent bulbs by 2011 most shops only have the new generation bulbs available. It would have been nice to have been offered some incentive to change to the greener option, but we’ve all got to grin and bear it for the sake of future generations.

We’re not a good household for getting huge benefits from energy saving light bulbs. We’ve always been energy aware and have turned off lights and appliances when they’re not in use. If you use old style spotlight bulbs the table Spreadsheet Calculator link.  will allow you to enter your details to check how long it will take to repay the investment in LEDs. It seems that the largest benefits are gained by households who have lights turned on for long periods of time and on most days.

Dimmable lights: In comparison to Halogens, dimming LED bulbs can be slightly complicated. LEDs need a constant current and run at a very low wattage. Whilst this is very good news for your electricity bill, it is also the reason why complications may arise when using them with a standard dimmer switch. You should factor in an additional £20 for a replacement dimmer switch in your calculations.

12V MR16 bulbs: These bulbs require a new driver/transformer for each fitting. These ensure a constant current and will help ensure the life expectancy of the bulb. Dependant on the wiring circuit for multiple bulbs you may be able to use one for all fitting, check with a qualified electrician. Once again you will need to factor in addition costs (£12-£20) dependant on your system.

I’ve used the prices gained from internet searches for LED bulbs in July 2011. I can amend the types of bulbs and prices if yours are not included.

Old style incandescent bulbs create light by passing electricity through a metal filament until it becomes so hot that it glows. Incandescent bulbs release 90% of their energy as heat.

CFL, "compact fluorescent light" are low energy bulbs , an electric current is driven through a tube containing gases. This reaction produces ultraviolet light that gets transformed into visible light by the fluorescent coating (called phosphor) on the inside of the tube. A CFL releases about 80% of its energy as heat.

LED lighting products use light emitting diodes to produce light very efficiently. The movement of electrons through a semiconductor material illuminates the tiny light sources we call LEDs. A small amount of heat is released backwards, into a heat sink, in a well-designed product; LEDs are basically cool to the touch.

Are you thinking of changing to LEDs? Or, have you already done so? I'd be interested in your thoughts.



  1. Hi Ian,

    * As I mainly need lights when there's no PV, I'm importing most of the energy used to run them, so it makes sense to be to minimise it!

    * The only incandescents I have left are in the oven, fridge & the (awaiting decorating) dining room/possible ground-floor bedroom for if/when we can't manage the stairs.

    * Early CFL were expensive and didn't pay back in cash, though there is some benefit to increased life and relatively cool running and different form factors: you can get a lot of light in a small space from a 2D or Circolux CFL.

    * I think current models are now cost effective over their (longer than incandescent) life. I'm looking for quality models though: it pays in the long term.

    * I have had to experiment to find suitable substitutes and usually replaced e.g. a 75W bulb with a "100W equivalent".

    * I'm on the second generation of GU10 LED bulbs. The first where OK, a bit blue, but the show-stopper was they glowed when turned off ... for hours! The 2nd-gen were expensive £12?ea a couple of years ago, but good 50W equivalent and should last my lifetime.

    * I've also used a LED halogen bulb replacement in a bedside light to good effect.

    * And of course all the house torches and cycle lights are LED ... with rechargable (Sanyo Eneloop long-storage-life) batteries.


  2. Hi Chris.

    I totally agree with your comments regarding the advances in bulb technology/costs and trying to minimise costs when there's no PV. I'm less certain about the benefits of adding to my costs with LED's which, for me, don't seem to make economic sense.

    Scenario 1: My kitchen has 8 MR16 12v spotlights. The replacement bulbs cost me £1.42 each and based on me using them for 2 hours a day 180 days of the year cost me £18.72pa based on my current electricity contract.
    If I was to replace the existing bulbs with LED equivalents @ £10.29 each, my energy costs would fall to £1.50 pa. Unfortunately, it would take me 5.25 years to recoup my investment.

    As I mentioned we are possibly not representative of the potential for savings from bulb change. The idea of us changing bulbs in bedrooms, cloakrooms, etc which rarely have any lights on for any length of time seems to be prohibitively expensive.

    For the movement I'm sticking with what I've got. At my age 5.25 years payback might be a step too far!

    Best regards

  3. @Icarus
    I found that I was replacing halogen GU10s so often that I reckon even £12-15 LED replacements pay back on the capital cost never mind the running cost. (This may be related to our mains voltage being a full 250V most of the time).

    It helped that I only have 3+4 GU10s in the house!

    Damon Hart-Davis has some useful info on LED lighting at http://www.earth.org.uk/LED-lighting.html (and much else useful on the site).

  4. @Chris B
    Very interesting comment about your mains voltage being 250v most of the time, I assumed that we ALL got 240v. As always, I realise that if ignorance really was bliss, I'd be the happiest man in the country!

    I had two good news items today.
    1. The paperwork arrived for my first ‘Winter Fuel Payment.’
    2. The local "Pound Shop" was selling 50W MR16 spotlight bulbs for 50p each.

    There is something fundamentally wrong with a system which allows taxpayers money to be given to everyone over 60, regardless of their need. Even more so that we’re not forced to use it to reduce our energy usage in future years.

  5. @Icarus "I assumed that we ALL got 240v."

    According to colleagues at work (and Wikipedia so it must be true), the country is supposed to be at 230V +/- 10%: 207-253V So my supply is within bounds, just. But it does mean that equipment designed for 230V is run very close to the limit. I suspect this applies particularly to incandescent bulbs, and now I think about it, possibly explains why I need the next CFL up to get similar light output: I've been running over-clocked incandescents!