Power label of appliances

A halogen bulb labeled 240 V, 50 W:

~ When connected to a 240 V voltage source, the bulb will shine with normal intensity. Power dissipated is 50 W

~ When connected to a voltage less than 240 V, the bulb will shine with less intensity and power is less than 50 W

~ When connected to a voltage more than 240 V, the bulb will shine with brighter intensity and power is more than 50 W. Life span of the light bulb will be shortened and the light bulb is burned out .

Task :
Find out why Energy Star compliant products use less electricity while helping stop global warming and save money?