Anyone who wants to buy a new refrigerator or washing machine is well advised to pay attention to the energy efficiency class: A category A appliance requires far less electricity than one in classes E or F. When it comes to lighting, however, the search for products is coming to an end quickly come to nothing in the high efficiency classes. Because most electronics stores, drugstores and online shops only offer lamps with a D, E or F label. Only the former Philips subsidiary Signify has brought a category A LED lamp onto the market. However, it is only available from very few retailers.
Until last September things were different, the shelves of the shops were full of LED lamps of the classes A+ and A++. Since then, however, the EU has tightened the criteria for classifying the lamps – A became an E or F, for example. The EU wants to give manufacturers an incentive to improve the efficiency of their products. Whereby LED lamps already perform quite well in terms of power consumption compared to halogen lamps or the old light bulbs.
And yet there is still room for improvement in terms of energy efficiency for LED lamps, says Philipp Strobel from the research center of the lighting manufacturer Lumileds in Aachen. “If you install more LEDs in the lamps than is usual today, you can achieve the same light output with less electricity.” The small semiconductor chips are the lamps’ actual light source – the “light-emitting diodes” that give LED lamps their name. The disadvantage: the products become more expensive with each additional LED. In return, however, the service life of the lamps also increases, since the individual LEDs are less heavily loaded.
The best LED lamp saves just 35 cents in 1000 hours
Another lever for more efficiency lies in converting the LED light into white light that is easily perceptible to the human eye. Because the lamps today usually work with LEDs that generate blue light. These chips get by with particularly little power. “In order to turn the blue light into white, the LEDs are equipped with special phosphors,” says Fabian Fligge, lighting expert at TÜV Süd.
They are integrated into narrow, yellow-orange silicone strips, which can be clearly seen inside the lamp. “Each manufacturer has its own mixture of phosphors,” says Fligge. The phosphors convert the blue light with red, green and orange components into a color spectrum that corresponds to the impression of white light.
“The trick now is to find a mixture that requires as little blue light – and therefore energy – as possible,” explains Fligge. The manufacturers can also specify the color temperature via the phosphor mixture, i.e. whether the light should be warm, neutral or cold white. All manufacturers are currently working on improving their mixtures, according to the expert.
Fligge is convinced that customers will be able to choose from a large number of category A and B LED lamps in the foreseeable future. You don’t have to make any compromises when it comes to light quality. “The legally required level of color rendering can also be achieved in the highest efficiency classes,” he says. If a manufacturer wants to go beyond that, however, it will be difficult. “We humans find it relatively difficult to perceive red tones. In order to reproduce red areas and bodies as well as possible, you have to generate more red light. However, this requires more electricity than, for example, green light,” explains Fligge.
And what happens if category A one day prevails as the new lamp standard? Will the EU then tighten the criteria again? No, says LED researcher Strobel. “The theoretical maximum efficiency for white light, which is easily perceptible to humans and covers the entire spectral range, is around 240 lumens per watt. LED lamps in efficiency class A achieve 210 lumens per watt, so they are already close to the optimum.” Nor is it to be expected that LED lamps will be replaced by a completely different technology. “Research has always examined alternative concepts, such as plasma lamps,” says TÜV Süd specialist Fligge. However, when it comes to handling, robustness and maintenance, LED lamps simply have advantages.
The question remains as to whether class A LED lamps are even worthwhile for households. The Signify product retails for about eight euros today, while comparable class D lamps are available for around one euro. The high-efficiency lamp does use a good third less electricity; to replace a 40-watt light bulb, it only needs 2.3 watts instead of around 3.5 watts as conventional LEDs. After 1000 hours of operation, however, this only saves around 35 cents.
According to this, the significantly higher purchase price with a daily burning time of four hours has only amortized after almost 14 years. However, the Signify lamp lasts twice as long as a cheap bulb according to plan. The class A lamp is only worthwhile where the lamps burn much longer per day, for example in shops or in restaurants. For households, on the other hand, much more is gained if they pay attention to maximum efficiency where power consumption is far, far higher – such as refrigerators or washing machines.