Lamps for household lighting will be grouped in energy efficiency classes on the basis of their energy consumption ratings. The Energy Label displays efficiency classes A to G: "A" stands for particularly efficient consumption, "G" for energy wastage. Stipulations regarding energy class assignments are set out in EU Directive 92/75/EEC.

The yardstick of efficiency used for lamps is luminous efficacy. It is the measure of how much luminous flux (in lumens) is produced from the energy consumed (in watts). An incandescent lamp manages a maximum of 14 lumen/watt and thus has a poor energy class rating. Energy-saving lamps have a luminous efficacy of up to 70 lumen/watt and thus comply with efficiency class A.

Lumens instead of watts

In future, luminous flux will be indicated as a performance characteristic for all lamps, initially in addition to wattage. Since 1 September 2010, lumen ratings on packaging are a legal requirement. Lumen ratings facilitate comparison of lamps. At present, a 11 to 12 W energy-saving lamp is the recommended replacement for a 60 W incandescent lamp (710 lumens). The "11 to 12 W" model is not an exact equivalent. But replacing the incandescent lamp with a lamp that produces at least 710 lumens ensures that the replacement is just as bright as the original.