No decision has been made to replace lightbulb classification from watts to lumens. The “luminous efficacy” of lightbulbs has for many years internationally been measured in lumens (measure of brightness) per watt (measure of power). This is the ratio of light out /energy in. There are currently information requirements placed on suppliers of lightbulbs that require the packaging to display the equivalent Watts of the lumen rating. However, as the demand for LEDs increases in the UK, lumens per watt is becoming a more appropriate measure of a lamp’s effectiveness in converting electricity to light.