Choose LEDs - Save the World! Kevan Shaw's response Dear Sir, I have just read this article (mondo*arc 36, Geoff Archenhold, p.68), and am extremely surprised that it survived your editorial scrutiny! There are a great number of statistical inconsistencies and some extremely poorly drawn comparisons. For example: Figure 2, Residential C02 emission, 22% attributed to lighting and appliances, elsewhere in the text 16% of total domestic energy is used by lighting, this is credited to the European Comission -DG Joint Research Centre. Later in the same section the 22% figure is used, does this mean that 6% of the domestic energy use is by miscellaneous toasters, hair driers, curling tongs, iPODs, etc? There are consistent references to LED energy saving light bulbs. These do not exist. In fact the article states as the last bullet point that LED based light sources which produce 60-70 Lumens per Watt wall plug efficiency need to be developed! The figure of 700KWh as the average annual usage of power for lighting is also interesting. Using figures in the article representing 16% of energy used, this multiplies out at 4,325KWh for total average electricity used domestically, not far from the average of 4,700KWh published by the UK Digest of Energy Statistics, 2005. The comparison to the BMW though is also interesting. Again working from the figures in the article the equivalent CO2 production for a year's total electricity used by a household is produced by driving 11,414.28Km in a BMW 316i, that is 7,134 miles compared with the UK average private mileage of 9,000 miles. The lighting component is equivalent to 1063 miles, therefore the effect in CO2 production of changing to low energy lamps typically is the same as driving 800 miles less per year! Quite frankly I would rather do this than lose the ability to light my home with incandescent light sources! On another thought, what will be replacing the heat produced by these wasteful incandescent lamps? I guess the extra heat will come from the central heating system, the boiler running that little bit longer each time the heating is used to maintain the same temperature in the rooms! Finally we have the old tag line of Lumileds having lab demos of LEDs achieving over 100 Lumens per watt, all very well but until these can be delivered into the market and operate at these efficiencies for prolonged periods at room temperature they remain vapour products! LEDs in the market are fairly stuck around the 20 to 30 lumens per watt range when all the correction factors are taken into account for operating temperature, achieving acceptable life and gear losses and no amount of mythical correction factors for "beam lumens" optical efficiency or other means of goal post shifting spin by LED manufacturers seems to be changing this efficiency figure. I am glad to see mondo*arc taking on some technical articles however I think you should take a close look at the content and quality before publishing! Regards Kevan Shaw Design Director KSLD