Light bulbs

Light bulbs last updated: August 2017


In order to be featured on Topten, light bulb models must comply with European Commission Regulation 1194/2012 with regard to energy labelling of directional lamps, light emitting diode lamps and related equipment, as well as meeting the following criteria:

 LED traditional shape (GLS) lamps: 

  • Energy rating of A+
  • Luminous efficacy of over 75 lumens per Watt

LED candles and GU10 spotlights:

  • Energy rating of A+
  • Luminous efficacy of over 60 lumens per Watt

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 14.05p/kWh.

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.

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).

Incandescent equivalent: the wattage of an equivalent 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.

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.

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