British Thermal Unit - Btu Law and Legal Definition

According to 10 CFR 420.2 [Title 10 – Energy; Chapter II -- Department of Energy; Subchapter D -- Energy Conservation; Part 420 -- State Energy Program; Subpart A -- General Provisions for State Energy Program Financial Assistance], the term British thermal unit (Btu) means “the quantity of heat necessary to raise the temperature of one pound of water one degree Fahrenheit at 39.2 degrees Fahrenheit and at one atmosphere of pressure.”