Historical clue formulations

• Utility bill unit — 2022-05-29
• Heating unit — 2020-12-22
• 1,000 large calories — 2019-03-10
• Unit on a utility bill — 2019-02-08
• Unit of 74-Across — 2018-01-14
• Gas bill unit — 2013-12-15
• Heat unit — 2011-05-09
• Gas bill unit — 2010-03-30
• 1,000 large calories — 1998-12-11
• Heat unit — 1994-02-03