Possible Clues:

• Heat unit, briefly
• Abbr. on an A/C
• Unit of energy related to Fahrenheit
• A/C fig.
• AC term
• 1,055 joules: Abbr.
• Heat unit (abbr.)
• BBQ heat rating
• Air-conditioner output: Abbr
• One of about 3,412 in a kW-h