What Philips documents
Philips, or rather its parent company Signify, documents this pack of ten under the product title LEDClassic 50W GU10 WW 36D ND 10PK with the EAN 8718696778265 and the article number 871869677826500. In the technical data for the pack of ten, the German product page gives 2700 kelvin, 355 lumens and 15,000 hours of rated lifetime. The detailed Signify product data sheet supplies the rest: 4.6 watts power consumption with an equivalent wattage of 50, a rated luminous efficacy of 77 lumens per watt, the colour code 827, a beam angle of 36 degrees, a colour rendering index of 80, a rated lifetime of 15,000 hours and 50,000 switching cycles. Under lamp properties it lists cap GU10, lamp shape directional reflector, bulb finish clear, bulb material glass, intended use indoor lighting and, as noted, the entry Dimmable No. For power consumption Signify gives energy efficiency label F, a consumption of 5 kilowatt hours per 1000 hours, a power factor of 0.5, a voltage of 220 to 240 volts and a frequency of 50 to 60 hertz. The warm-up time to 60 per cent light is 0.5 seconds, and the peak intensity at the centre of the beam is 700 candela. The lamp measures 54 millimetres in height and length and 50 millimetres in width, and the pack weighs 0.45 kilograms net. The sheet lists a guarantee of 2 years and the EPREL registration number 387358. This data sheet gives no mercury value, although Philips states it explicitly as 0 milligrams on other sheets in the Classic range. Philips also sells the same light bulb in smaller packs, and the pack of three gives identical figures of 2700 kelvin, 355 lumens and 15,000 hours.
Not dimmable, and with ten lamps that weighs more
The product title says it before the data sheet does: WW stands for warm white, 36D for the beam angle, 10PK for the pack size and ND for not dimmable. The data sheet spells out the entry Dimmable No once more. With a single lamp, a wrong purchase is annoying but quickly put right. With ten lamps it usually affects a whole room or a whole track, and the chance that a dimmer sits somewhere in the household after all rises with every lamp holder. A non-dimmable light bulb on a leading-edge or trailing-edge dimmer can flicker, hum, start with a delay or stay off entirely in the lower part of the range, and the dimmer itself is not designed for this either. Ten lamps together draw 46 watts, which is electrically something different from a single lamp at 4.6 watts. Even if an existing dimmer seems to cope, that does not change the fact that Philips does not approve the lamp for dimmer operation. If you really want to dim, Philips offers a counterpart in the same shape: the WarmGlow pack of six with the product title LED CLA 50W GU10 C90 WW 36D WGD 6CT/4 gives, according to its data sheet, 3.8 watts, 345 lumens, a colour rendering index of 90, a colour range of 2200 to 2700 kelvin, a power factor of 0.84 and the entry Dimmable Yes. If you would rather control brightness without touching the wall, consider smart lighting instead of a dimmer, where the control sits in the lamp. For lamp holders with E27 rather than GU10, we have worked through the same question in the data check on the Osram Superstar Plus E27.
GU10, GU5.3 and MR16: the most common wrong purchase when swapping spots
GU10 is a mains-voltage cap. Two sturdy pins 10 millimetres apart are pushed into the lamp holder and locked with a quarter turn. This fits the data sheet figures of 220 to 240 volts and 50 to 60 hertz: the lamp hangs directly on the household supply and needs no transformer. GU5.3 looks almost identical from below, but has two thin pins 5.3 millimetres apart, is only pushed in rather than turned, and runs at 12 volts behind a transformer or electronic converter. Strictly speaking, the designation MR16 is not a cap specification at all but the shape of the reflector, although in the trade it is often equated with 12-volt spots. Philips itself calls the shape of this lamp PAR16, which fits the data sheet width of 50 millimetres. In practice that means: before ordering, look into an empty lamp holder and count not the watts but the pins. If the cap does not fit, even the nicest colour temperature will not help, and a GU10 lamp must never go into a lamp holder wired for 12 volts. A second point concerns the space above the ceiling: the lamp is 54 millimetres tall, and the lamp holder itself comes on top of that. In shallow ceiling voids or directly under insulation this can get tight. If you are drilling new holes anyway, it is worth looking at complete recessed luminaires rather than just swapping light bulbs, see our data check on the Paulmann Nova Plus recessed luminaire.
36 degrees and the question of how many spots a room needs
36 degrees is a medium beam angle: narrower than an ordinary lamp that fills the room in all directions, and clearly wider than an accent spot at 10 or 24 degrees. It is easy to calculate with. With a ceiling height of 2.40 metres and a worktop at 0.90 metres, the distance is 1.50 metres, and the light cone measures about 0.98 metres across there. On the floor, that is 2.40 metres below the ceiling, it is about 1.56 metres. To avoid dark stripes between the circles, the cones should overlap, which in practice works out at spot spacings of about one metre. Ten lamps of 355 lumens each give 3550 lumens in total, provided they all actually sit in the same room. That is a solid basic setup for a medium-sized kitchen and, for a large living room, more like the base level of brightness, to be supplemented by floor and table lamps. What matters here is the peak intensity of 700 candela: directly under the spot it is bright, and towards the edge of the cone the brightness falls off. A row of spots therefore does not replace a ceiling light that lights a whole surface; it creates a pattern of brighter and less bright zones. How much light your room needs overall is covered in our overview of lumens per room, and if you still think in watts, you will find the conversion in the lumens-to-watts chart. The 2700 kelvin is deliberately warm and suits living spaces, as we explain under colour temperature and kelvin.
Which Philips GU10 you actually have in front of you
Hardly any lamp family is as easy to mix up as the Philips GU10 spots. They are all somehow called 50 watt, they all have 36 degrees, and the values still differ. The pack of ten discussed here is the basic consumer variant with 4.6 watts, 355 lumens, 2700 kelvin, class F, 15,000 hours and not dimmable. Its professional twin, the Corepro LEDspot 4.6-50W GU10 827 36D with the material number 929001215232, gives exactly the same 355 lumens, 2700 kelvin, 36 degrees, colour rendering index 80, class F and likewise Dimmable No. The Essential LED 4.6-50W GU10 827 36D with the material number 929001215208, by contrast, has an identical 4.6 watts, an identical 2700 kelvin and an identical 36 degrees, but reaches 395 lumens instead of 355. If you only look at watts and kelvin, you miss this difference completely. The specialists lie even further apart: the MASTER LED ExpertColor 5.5-50W GU10 927 36D delivers the same 355 lumens at 2700 kelvin, but reaches a colour rendering index of 97 and 40,000 hours, and in return drops to energy class G with 64 lumens per watt. And the ultra-efficient line shows how much technology is now possible: the sheet for the LEDClassic 50W GU10 WH 36D ND UE SRT4 gives 2.1 watts, 375 lumens, 178 lumens per watt, energy class A, a rated lifetime of 50,000 hours, a 5-year guarantee and 3000 kelvin instead of 2700. The quickest check is therefore the printed product title: WW versus WH versus CW for the colour temperature, ND versus DIM for dimmability, UE for the ultra-efficient design and the number before PK or CT for the quantity. One assignment does remain open, however: Philips does not print Amazon numbers on its data sheets. That this listing corresponds to the pack of ten with the EAN 8718696778265 rests on the fact that all the features named in the listing, that is ten pieces, 50 watt equivalent, warm white, 36 degrees, 15,000 hours and explicitly not dimmable, fit exactly this one Philips product. If a different product title is printed on your pack, the values for that pack apply.
What the data does not answer
For a consumer product the data sheet is unusually complete, but a few gaps remain. First, the mercury content is missing, which Philips states for other Classic lamps. Second, the sheet mentions EyeComfort, but gives not a single numerical value for flicker or the stroboscopic effect against which this claim could be checked. Third, the consumer sheet says nothing about whether the lamp may be operated in closed or insulated recessed luminaires. The professional data sheet for the identically specified Corepro variant at least gives a maximum case temperature of 72 degrees Celsius, which shows that heat dissipation is an issue even at 4.6 watts. Fourth, the power factor of 0.5 stands out. It plays no role in the household electricity bill, but it does for the load on the circuit when many lamps are connected in parallel. And fifth, a look at the advertising claims is worthwhile: the wording of up to 15 years appears not only in the listing text but on the Philips data sheet itself. It is a conversion of the documented 15,000 hours and assumes a particular daily burning time, which Philips does not state anywhere. The figure of 90 per cent energy saving is a calculation against the halogen predecessor: 4.6 instead of 50 watts is about 91 per cent less power consumption, but this percentage does not appear in the data sheet as a verified individual value. How we handle such claims is explained in how we work.
Our assessment
For the most common case, namely a kitchen, hallway or living room with fixed GU10 spots and no dimmer, this pack of ten is an unfussy, suitable solution. You get the same colour point ten times over, which is the real advantage when buying individual lamps later: nothing looks mismatched when all the spots come from the same batch. The 355 lumens correspond to what a 50-watt halogen spot delivered, so the switch is hardly noticeable visually. Ten lamps of 4.6 watts each give 46 watts of connected load, which at three hours a day comes to about 50 kilowatt hours a year, and our page on LED power consumption and running costs shows how to put that in context. If you do dim, though, leave this alone and go for the dimmable WarmGlow variant. If you want to see food, wood and textiles in true colours in the kitchen, a colour rendering index of 80 is only standard, and the ExpertColor line with Ra 97 offers clearly better colour rendering, but you pay for it with energy class G. And if you want to seriously reduce consumption, check whether the ultra-efficient line with 2.1 watts and class A is available in the colour temperature you want, because there the jump is not a few per cent but more than half. Energy class F is the most honest criticism of this pack of ten: 77 lumens per watt is solid mid-range today, no more. So this pack is not bought for peak values but for the quantity, the uniform colour temperature and the fact that 36 degrees and PAR16 fit into almost any existing GU10 lamp holder. We collect matching lamps and room ideas in the home lighting section.
Further reading: Linkind GU10, whose data sheets contradict each other on dimmability, Philips LED Classic E27 filament in the data check, Osram Superstar Plus E27 as a dimmable alternative, Paulmann Nova Plus recessed luminaire, How many lumens your room needs and Understanding colour temperature and kelvin.