22.5% small 3-phase motors, 52.5% large 3-phase motors. It is likely that a modern installation would have less opportunity: almost no incandescent lighting, partly high-frequency fluorescent lighting (no saving), some variable speed drives (no saving), higher motor efficiencies (so less waste to save). A northern European installation would not have the large number of small single phase motors for air conditioning. Energy saving is possible with older lighting, at the expense of lower light output, (e.g. incandescent or fluorescent and discharge lighting with inefficient ballast or control gear). Therefore, older commercial and office premises may save more than modern buildings or industrial sites. However modern lighting systems (typically LED) will save significantly more energy due to higher efficiency than energy saved on older lighting systems following installation of a voltage optimiser. Obtaining energy savings with a voltage optimiser used with modern lighting systems is very questionable. Modern electronic switching controllers for LED or fluorescent lighting systems are designed to run the lights at optimal light output and longevity with high efficiency. Variations in supply voltage will therefore not make any difference to the overall energy use of these types of lights. However, there exist types of low cost LED and fluorescent lamp controllers which reduce the voltage by shedding energy as heat (e.g. multiple LEDs in series with a series resistance). Varying the supply voltage would affect the energy used by these types of lights, but these type of lamps are generally low power and the light output would also be affected. Worked example A typical 100 watt incandescent lamp has an efficiency of no more than 17.5 lumens per watt (l/W) and will therefore produce 1750 lumens at its rated voltage. A typical modern LED lamp has an efficiency of about 150 lumens per watt, and therefore requires no more than 12 watts for the same light output. According to Lamp rerating formulae, reducing the voltage across an incandescent lamp by 10% reduces the power (and therefore energy) by about 16% and reduces the light output by about 31%. Therefore, a voltage optimiser that reduces the voltage on an incandescent lamp by 10%, will reduce the energy by 16% and light output by 31%, producing only 1210 lumens and consuming 84 watts. Changing the incandescent lamp to an LED lamp with similar light output would have reduce the consumption more effectively, down to 12 watts. Furthermore, since the light