Selection Criteria

Light bulbs

 Light bulbs last updated: 13/02/2014

Light bulbs are divided by type into CFL and LED lamps, with the following sub-categories:


  • E27 (large screw) cap
  • B22 (bayonet) cap
  • E14 (small screw) cap


In order to be featured on Top10, light bulb models must comply with European Commission Directive 2009/125/EC with regard to energy labelling of directional lamps, light emitting diode lamps and related equipment, as well as meeting the following criteria:


CFL lamps:


  • Energy efficiency class A
  • Luminous efficacy:
    • Sticks E27/B22/E14 and Bulbs E27/B22: minimum. 50 lm/W, if length > 105 mm
    • Sticks E27/B22/E14 and Bulbs E27/B22: minimum 40 lm/W, if length < 105 mm
    • Bulbs E14 and Candles E27/B22/E14: minimum 40 lm/W
    • Life time: mínimum 12,000 hours
    • Switching cycles: mínimum 50,000
    • Warm-up time: maximum 60 seconds


LED lamps:


  • Be for domestic use
  • Luminous efficacy:
    • Up to 300 lm: minimum of 45 lm/W
    • 300 to 470 lm: minimum 50 lm/W
    • Above 600 lm: minimum 60 lm/W
    • Life time: minimum 20,000 hours
    • Switching cycles: minimum 50,000
    • Colour Rendering Index: minimum 80


Inefficient model selection

The “inefficient model” is an anonymised halogen retrofit bulb equivalent to the most common output in each sub-category. This allows comparison with the least efficient technology available.





Annual energy consumption: the energy consumption, in kWh, per year based on 1,000 hours of use.

 Annual running cost: the annual running cost in electricity for the product based on the quoted annual energy consumption and an electricity cost of 14.5p/kWh.

 Average retail price: the average market price of the product determined by checking prices for the specific model advertised by at least three retail websites.

 Colour temperature: the light colour appearance of a lamp can be defined in terms of its colour temperature in degrees Kelvin (K). There are three main colour groups: warm whites < 3300 K; neutral whites 3300 K - 5000 K and daylight whites > 5000 K.

 Colour of light: the colour group of the bulb as defined above.

 Dimensions: the unpacked dimensions of the product in mm.

 Dimmable: whether the bulb can be dimmed using a standard lightswitch or dimmer switch.

 Energy label: the energy efficiency class according to the EU Energy Label. The classes range from A++ (most efficient) to E (least efficient).

 GLS wattage equivalent: the wattage of an equivalent GLS (incandescent) bulb.

 Life expectancy (hours): the number of hours the bulb is expected to last, defined as the point at which 50% of bulbs will have failed.

 Luminous efficacy: the efficiency of the bulb in light output (lumens) per unit of power (watts). This is used to determine a lamp’s inclusion in Top10 and to rank the featured models.

 Shape: the form of the lamp. Including bulb, candle, globe, golf ball, spiral and stick types.

 Switching cycles: the number of times the lamp can be switched on and off before failure. According to Regulation (EC) No 244/2009, a switching cycle consist of a period comprising 1 minute on and 3 minutes off.

 Warm-up time: the maximum time by which the bulb will have reached 60% of its maximum output.

 Wattage: the rated power consumption of the lamp in Watts.


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