Use only the amount of light you need.
For maximum lighting efficiency use a higher lumen-per-watt bulb. Watts measure the amount of energy going into a bulb. Lumens measure the light output or brightness of a bulb. This information is printed on bulb packages. To determine efficiency, divide the lumens by the watts of electricity used.
For example, the efficiency of a 100-watt bulb measuring 1710 lumens would be 17.1 lumens-per-watt.