Economics, LED Lighting and Sustainability

Economics and sustainability do not sit comfortably together.  Fossil fuels are convenient and after more than a century of development the devices which consume them are reasonably efficient and in some respects cheap.

Things that are tagged as "sustainable" or "green" often have a premium either paid directly by the owner or indirectly by a third party in the form of a subsidy.  Ideally, sustainable technologies should deliver the same benefits for the same cost as traditional technologies.

My experience with LED lighting suggests that it meets these criteria.  I bought my first LED lamp approximately 4 years ago and it did not win the hearts and minds of my family.  I'm guessing but I think it produced 50 - 60 lumens per watt which was only a modest improvement on CFLs which lit the house, however, the real problem was the fact that the light came from a surface rather than a sphere, thus the diffuse light reflected from ceilings was lost.  About two years later, some small LED globes started appearing with an output of around 400 lumens and maybe an efficiency of 60 - 70 lumens/watt.  These worked well and some 10 watt CFLs were replaced with 5 watt LEDs.  Recently, the "right" product appeared in the form of a globe lamp with an output of around 900 lumens and an efficiency of 90 - 100 lumens/watt.  We are now replacing 20 watt CFLs with 10 watt LEDs.

The benefits of moving from CFL to LED appears in the electricity bill, we currently consume about 1,500 kwh/year making the bill, excluding standing charges, roughly £250/year.  I extracted the graph above from my account on the energy suppliers website.  It needs treating with caution as I'm not sure it compares like-with-like.  I'm guessing that the "similar house" means one in the same postcode area and that the "efficient house" is the lower quartile for that postcode area, so all the graph tells you that our home uses electricity than our neighbours, possibly because we have LED lighting.

Let's take this experience to some illogical conclusions.   Say, an investment of £250 in LED lighting reduces a home's electricity consumption by 200 kwh/year most of the reduction taking place in winter when the demand for energy is highest.  Compare this with a hypothetical rooftop PV installation costing, maybe, £5,000 which produces 2,000 kwh/year mostly during the day in summer when the demand for energy is lowest.  Which technology gives the best environmental outturn?