It’s mandatory for suppliers to put on energy labels on the lighting products if they want to sell them in the European Union countries, which is regulated by EU directive No 874/2012 (issued on 12 July 2012) and some other implement  directives. The energy label should contain the energy efficiency, weighted energy consumption and suppliers name and  trade mark and supplier’s model identifier as image 1 shows for electrical lamps. While the label is printed on the  package, and the information except for energy efficiency is included elsewhere on the package, that information may be  omitted from the label like image 2.

    Image 1                                             Image 2

Calculation for energy efficiency class:

The energy class of electrical lamps shall be determined by the energy efficiency index (EEI) as the following table shows:

EEI= P_(cor)/P_(ref)

*P_(cor) is the rated power for models without external control gear and the corrected rated power for models with external control gear.

*P_(ref) is the reference power obtained from the useful luminous flux(Φ_use) of the model.

The calculation chart attached is for most commonly seen LED lamps. 

Calculation for energy efficiency class

You can also find the directive EU 874/2012 here.