Who left the lights on?

Two things prompted this blog post. The first is an experiment I’ve been doing on my housemates, in which I go round switching lights off when people aren’t in a communally used room (which I count as kitchen, bathroom, front room, study). I have done this on 10 evenings when I’ve been home over the last month. Every evening I have done the experiment, I’ve switched off at least 10 lights. Rather disappointing given that we would all self-identify as being environmentally friendly. Anyway… I’d vaguely been wondering about lighting, and then yesterday whilst looking for data on energy consumption by fuel type for a lecture I was giving, I came across some interesting data from BEIS on appliance ownership. It’s from their annual publication “Energy Consumption in the UK”, and is reproduced below.

appliances per household

As is obvious from the table, we own far more electrical appliances than we did in 1970. The increase in appliance ownership is particularly striking in two sectors; lighting, and consumer electronics. The data on lighting appliances is shown in more detail below (the BEIS spreadsheet I got the data from is available here).

lighting appliances

We can see that the increase in ownership of both energy saving bulbs and halogens corresponds closely with the decline in incandescent light bulbs. The EU phase out of incandescent bulbs dates from 2009, and this accelerated the shift that had already started. The increase in halogens would be concerning from an energy efficiency perspective, but they are being banned from sale in 2018, and it’s likely that LEDs (which are much more energy efficient) will fill this void.

The other striking thing about the data is that we have a lot more lights than we did in 1970 (16 per household in 1970, compared to 27 in 2016). What isn’t yet clear is the rate at which improvements in switching, wireless technologies and controllability of lighting are going to occur. It’s certainly the case in my household that a lot more lights are being left on than used to be the case, and this seems to be largely due to preferences relating to ambience and task lighting, combined with the fact that it then becomes necessary to hit several light switches in different parts of the room. Locations of light switches on mains electrical circuits feature in building regulations (there needs to be a light switch by the entrance to a room), but it is difficult to see how regulatory requirements can keep pace with changes in consumer purchases and preferences for lighting.

My guess is that at some point in the next 5 years, our hunger for more lights will outstrip the use of more energy efficient lighting, and that unless the controllability of lighting improves significantly, the total energy use from lighting appliances is going to go up.

2 thoughts on “Who left the lights on?”

  1. I know some people find fluorescent lights makes them feel unwell ( I think largely due to flicker) but I wonder if there may yet be long term health implications of LED Lighting. Certainly when I get eye strain the harsh light from LEDs is uncomfortable. If we look at the spectral distribution of ‘white’ light from an LED it’s actually nothing like the white light you’d get from the sun or even incandescent bulbs which have a smooth distribution from red through to blue. LED light is a harsh mixture of a few narrow bands of light and could be considered ‘fake’ white light. I strongly support anything to cut energy consumption, but it’s not unknown to find new sustainable technologies have unintended consequences, the impacts of biofuels for example.


    1. The spectra from different light sources is a big old subject, and not one I know much about. But I asked a colleague about it, and he sent me a few diagrams. I’ll upload these if i can work out how!

      The first thing that I learnt from the diagrams is that no type of light bulb has a spectra similar to sunlight. That’s not to say that it isn’t possible to mimic sunlight, simply that it’s probably not a good idea to start from the perspective that one type of light bulb is better from this perspective.

      The second diagram shows the spectra available from a range of LED bulbs. This shows that it should be perfectly possible to create an array that is similar to sunlight.

      The other thing I wonder is whether having a light source that is like sunlight is necessarily a “good thing”. After all, we get damaging UV radiation from sunlight, but we also sunlight to synthesise vitamin D.


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