### Question
How does the law define lamp efficacy?


### Answer
Under *42 U.S.C. § 6291*, **lamp efficacy** is defined as:

> the lumen output of a lamp divided by its wattage, expressed in lumens per watt (LPW)

#### Citation:
  - *42 U.S.C. § 6291*
  - Heading: **CHAPTER 77-ENERGY CONSERVATION > SUBCHAPTER III-IMPROVING ENERGY EFFICIENCY > Part A-Energy Conservation Program for Consumer Products Other Than Automobiles**

