The term 'GAS UNIT' can be broken down into two crossword solutions: LITER and THERM. A liter is a unit of volume in the metric system, equal to one cubic decimeter, or 1, 000 cubic centimeters. It is also equal to 0.264172052 US gallons. A therm is a unit of energy used in the United States and is equal to 100, 000 British thermal units (BTUs). It is also equal to 29.3 kilowatt-hours. Both of these units are commonly used to measure the amount of gas consumed.