Do we want invisible light?

I went to a talk about energy efficient lighting on Tuesday given by Dr Charlotte Louise Jensen, a Danish researcher who wrote a PhD on the subject. She spoke about her experiences interviewing householders in Denmark about their lighting systems and how they use them. It is quite possible to use energy efficiency light bulbs in a very inefficient way (I have seen a bedroom lit by a grid of recessed ceiling lights, which would have used 80W even with LEDs). She suggested that to get the best from energy efficient lighting we need to learn about the new technology, experiment and share our ideas. Here are some ideas to share.

Are these lights LEDs or incandescent light bulbs?

LEDs or incandescents?

On holiday last week in the New Forest we had a nice lunch in the White Buck in Burley (highly recommended) with rather elegant lighting in the bar. Oh, that's a shame, I remarked to my beloved, they're still using incandescent lights - and then I realised they weren't. It isn't clear in my photo but each of the candle-shaped lamps in this candelabra actually contains 3 little LEDs.  Of course it isn't really necessary that energy saving light bulbs should look like old fashioned ones, but it certainly helps when you don't have to change the fittings and chandeliers at the same time as the bulbs.

Dazzled by the new street lights (not)

Cambridgeshire county council is running a project replacing street lights to save energy (actually it's a PFI so Balfour Beatty is running it) - and so are many other councils around the country. Street lighting is a very visible use of energy and excites a lot of opinions, both on the side of making savings and on the side of ensuring adequate lighting. The new lighting in Cambridgeshire is expected to halve energy use while maintaining adequate lighting levels. How is this possible and how much difference will it make?

LED lighting for health

It has come to my attention, through my consulting work, that about a quarter of households use significant electricity for lighting even in the middle of the day, when sunlight is free. Perhaps this should not be such a surprise as big windows do lose a lot of heat even with double glazing (though triple glazing is very good). Artificial lighting styles are surprisingly different across cultures. In Japan, fluorescent lighting is preferred in living rooms because incandescents are not bright enough - the Japanese like them for the evening, or for hotels and restaurants [1]. This is very reasonable when you consider the health benefits of strong light (preferably daylight, i.e. 'cool' light  including a bit of blue) during the day. It helps to regularise our sleep patterns and can even reduce symptoms of dementia [2]. However, such bright lights are not good for us in the evening when they can contribute to insomnia, so much so that NASA are testing colour changing lights on the space station to help the astronauts sleep [3].

How Eco is an eco-halogen light bulb?

A friend of mine asked me to investigate so-called 'eco' halogen light bulbs she had seen in various outlets. Halogen bulbs use a little less power than incandescents but are not nearly as efficient as compact fluorescents  (CFLs) or LEDs - eco is a relative term. It turns out that the eco-halogens (from Osram) have energy rating C whereas compact fluorescents and LED light bulbs are normally rated A and there is a world of difference between A and C - a factor of at least 3 in electricity use.

On Christmas Lights

A friend we visited last weekend had some solar powered outdoor Christmas lights around a tree in their front garden. They weren't working because the weather has been so bad - not enough sun. In any case the size of the solar panel feeding their battery was miniscule - maybe 20cm on a side. LED lights are the most efficient we have now but they don't make light out of nothing. I checked our solar panels - we are currently getting about 1.5 kWh/day from 9 panels so 0.17 kWh/panel. To power a 10W string of lights for 4 hours you would need 0.04 kWh so a quarter size panel. This one was probably about a fifth the size it needed to be. This got me thinking about other ways - not necessarily totally practical - to power outdoor lights. Also I thought I'd do a reality check on carbon emissions from candles versus LED lights.

Daylight saving and energy saving

Weekday electricity usage 2011 averaged over Mon/Tue/Wed around the clock change. Sunset time is for London.

We switch to Daylight Saving Time tomorrow (March 25th). This changes our electricity consumption patterns. The Lighter Later campaign would like us to switch to DST all the time and DST+1 in summer, for various reasons including a predicted reduction in electricity demand. Is this estimation reasonable?

Christmas trees and Christmas lights

I love to see the fairy lights on our Christmas tree, and the colourful illuminations down the high street.  With dusk falling in late afternoon we need a little something to brighten up the gloom don't we? It's only once a year after all. However, energy bills are rising and climate change is a persistent and increasing threat, so it might be worth a quick check to see how much these luxuries are costing us. Also the Christmas tree quandary - is a real tree lower in carbon emissions than an artificial one, or not?

Should I buy LED bulbs?

A friend remarked to me the other day that LED lights are cheap enough now that they can pay for themselves (replacing a halogen lamp) within a year, at least for for use cases where the lights were on most of the time, as in many shops and offices. I checked this out and it is true. However, what about replacing a CFL bulb  (the usual energy saving light bulbs). How much less power does the LED take, is it really cheaper taking into account the high up front cost and is it really greener overall?


Even the power consumption question is not so easy to answer. LEDs are normally compared to halogens rather than CFLs or incandescent. For my calculations I have compared (both from Amazon):

• 6W LED allegedly equivalent to  a 50-60W halogen (1) (£60 for a pack of 6 so £10 each)
• 18W CFL allegedly equivalent to an 80W incandescent (2) (£12 for a pack of 2 so £2  each)