Low Energy Lighting

How much of our electricity use is for lighting? Do low energy bulbs really make a difference?

On average about a sixth of our electricity bill is due to lighting (as of 2012). Replacing incandescent bulbs with low energy bulbs can cut that by 80% so you can expect to reduce your electricity bill by at least 10%. However, this is only an average – some households use a lot more lighting and some a lot less.

Changing lamps has a big effect on the reducing the national electricity demand, especially the winter evening peak. It means fewer power stations have to be kept on line to ensure demands can always be met.

How long will it take for a low energy bulb to pay for itself?

Suppose you replace a 60 W bulb with a 12 W CFL and you use it 3 hours/day. Your electricity costs 14p/kWh. The new bulb will save you

  (60-12)/1000*3*365*0.14  = £7.30 /year 

You can get one these days for about £2 so that pays back in about 3 months just on electricity alone. Tungsten lamps only last about 1000 hours so you’d be replacing them each year whereas good CFL’s last for over 10,000 hours.

There is an easy to use savings calculator here (My Green Lighting)

If you were to use an LED the saving would be a little more but they cost more too so the payback will be longer but they do last a very long time.

What does the phase out of incandescent bulbs mean – how come I can still get them?

The EU lighting efficiency rules mean that ordinary incandescent bulbs are no longer available – except that old stocks can still be sold. Since the schedule for phasing out the bulbs was publicised well in advance, many retailers made sure they had lots of stock. But they will go eventually.

You can still get incandescent bulbs for special purposes, where there is no low energy equivalent.

Is it worth buying LEDs rather than CFLs (since they cost more)?

That rather depends on the situation. LEDs have advantages such as:

  • They come on instantly (though some CFLs are a lot better than others in this respect).
  • Switching them on and off frequently does no damage – so they are good for motion sensing lights such as security lights that switch on and off very often
  • They use even less power than CFLs
  • The dimmable ones are a lot more efficient than the dimmable CFLs

Why is ‘warm white’ a cooler temperature than ‘daylight’?

It is a bit counter-intuitive but we think of daylight as cool whereas candle light is warm – though in fact the colour depends on the temperature and the sun is a lot hotter than a candle! The table below shows approximate colour temperatures. See also this advice from ec.europa.eu on bulb characteristics

ColourTemperature
Warm white (incandescents)2700K
Cool white4000K
Daylight6000K

If you are replacing one of a set of lights it is quite important that they all have a similar colour, otherwise the odd ones will stand out. If you are replacing halogens, they are probably close to warm white, around 3000K. See also advice from www.lightbulbs-direct.com

Are daylight bulbs more efficient?

All fluorescent bulbs and many LEDs use different types of phosphor to adjust the colour of the light produced. The phosphor absorbs UV light and emits in a different wavelength. The choice of phosphor is important to the efficiency of the bulb. However, the efficiency is not particularly related to the colour.

When should I use daylight bulbs rather than warm white?

Daylight bulbs are often favoured by elderly people and also by artists and photographers because they give good colour rendering. They are good for work spaces but you might find t hem a bit harsh for a living room or bedroom, unless you were putting them in a coloured shade.

Do plants like low energy lights?

Incandescent bulbs mimic light at sunset – whereas cool white or daylight bulbs are a better simulation of sunlight. Plants generally prefer fluorescents to incandescents.

When it come to LEDs, however, you need to get a full spectrum bulb rather than an ordinary white one, because some LEDs emit only in narrow bands for red, green and blue to make up white – it looks white to our eyes but plants can tell the difference. In fact you can get specialist horticultural LEDs that produce light in just the wavelengths plants like best – blue and red but no need for green. Here are some reviews (www.ledgrowlightsgq.co.uk) and a discussion on gardening.stackexchange.com

Aren’t halogen bubs low energy too?

Halogens are better than incandescents but not nearly as good as fluorescents and LEDs. Typically halogens are energy class B whereas incandescents are C and CFLs or LEDs are A. However there is a big difference between A and B. For example 50W halogen would give as much light as a 70W incandescent but an equivalent LED would be no more than 13W. There is a useful comparison chart on www.which.co.uk

Why are LEDs so big and heavy?

LEDs need quite a lot of electronics to work and this needs to be kept cool – otherwise it will drastically shorten the life of the bulb. So they tend to have large and heavy heat sinks – generally speaking the more watts the bigger the heat sink. However, the design is also important and there are some interesting innovations available.

Can LEDs replace ordinary bulbs, not just spots or reflectors?

Yes. There are a good number of omni-directional LED bulbs available, looking more and more like the old fashioned incandescents in shape. For example see the My Green Lighting website

You can even get bulbs with a thin strip of LEDs to simulate an old-style filament. They aren’t cheap though. Here is an example from My Green Lighting (if this link does not work try looking for 'filament led')

Can I use LEDs with dimmer switches?

Some LEDs can be used with dimmers but not all. You should check the label. Also, it may be that you need to replace the dimmer switch as well. Older switches designed for incandescents may not work with LEDs. See also http://www.lightbulbs-direct.com/article/led-dimmer-switch-compatibility/

Can I use LEDs to replace 12V MR16s?

There are a few MR16 equivalent LED bulbs available but not as much choice as you get with other types. Also, you may need to replace the transformer as well as the bulbs because many transformers have a special soft start mode that restricts the current until the bulbs get going – but LEDs draw so little the transformer does not realise it has.

If you do find you need to change the transformer it may be cheaper to get an electrician in to convert the light fixture to normal 240V.

How should I dispose of LED light bulbs?

LEDs count as electronics so should be disposed of like other electronics or WEEE. In Cambridge there is special recycling for batteries and bulbs at many recycling points.

How are the new LEDs better than old ones? What can we expect for future developments?

LEDs are improving both in size/shape and cost. You can now get LEDs that are very good replacements for old-style incandescents, if that is what you are looking for. Newer ones are often cheaper – so just because a bulb is cheaper does not mean it is poor quality. The market is changing very quickly at the moment and new designs are sometimes introduced and become obsolete within a year! However, build quality is very important and poorly made bulbs won’t last long.

Should I worry about the mercury if I break a CFL?

A fluorescent bulb may contain up to 5 mg of mercury – 100 times less than in a standard mercury thermometer. This is barely enough to cover the tip of a ball point pen and it isn’t enough to do you any harm unless you break an awful lot of bulbs. However, the standard recommendation is to air the room for 15 minutes and wear gloves for the cleanup. Put the bits in two layers of plastic bag. The broken glass is more likely to do you damage than the mercury. See also advice from recolight (who recycle Cambridge's bulbs)

How should I dispose of CFL and fluorescent light bulbs (unbroken)?

Here in Cambridge there are recycling points for batteries and low energy light bulbs at some recycling centres. See https://www.cambridge.gov.uk/light-bulbs for more information. Our bulbs are handled by Recolight

Is it true that turning fluorescents on and off shortens their life?

Yes – though some are better than others in this respect. If you use a light for less than an hour or so at a time, on average, then it is likely the life of the bulb will be more limited by the number of switches rather than the total hours on. But even so it should survive for 3000 cycles at the very least – so 3 years at 3 times/day. And it will still be saving you energy, and money.

Suppose you use a 12W CFL instead of a 60W incandescent and you only use it for 10 minutes at a time and the bulb only lasts 3000 cycles – the worst case. The bulb will last for 500 hours, saving you £3.36 – and you can buy one for less than that so you still have a net saving.

However, LEDs are often better for lights triggered by presence sensors, such as security lights, unless they are specially designed to last many switching cycles

Unfortunately not all bulbs seem to have the number of switching cycles displayed on the packaging – in which case one should assume the worst. The ones that are designed for many switching cycles will be labelled as such.

Can I replace straight fluorescents with leds

Yes! You can now get led lights that fit into fluorescent fitting. There is a complication in that fluorescent fittings include a ballast that helps start the tube. LEDs don’t need this ballast and if you leave it in the circuit there is some cost because the ballast uses some power all the time – generally no more than 5W. However, bypassing the ballast is a fiddly wiring job. So you can get a bulb that work with the fluorescent ballast – a simple replacement – or you can get a bulb that doesn’t, which means you have to do some wiring but you save even more energy.

Where can I get more information

How to read the packaging – efficiency, lifetime, colour etc.: https://ec.europa.eu/energy/en/topics/energy-efficiency/energy-efficient-products/lighting

Good places to buy in Cambridge