British Thermo Unit. The quantity of heat to raise the temperature of one pound of water by one degree Fahrenheit.
| Coal | BTU's |
| 1 lb. | ~12,500 |
| 1 Ton | ~25,000,000 |
| Electricity | BTU's |
| 1 KW/hr | 3,413 |
| OIL | BTU's |
| 1 Gal. #1 Fuel | 136,000 |
| 1 Gal. #2 Fuel | 138,500 |
| 1 Gal. #3 Fuel | 141,000 |
| 1 Gal. #5 Fuel | 148,500 |
| 1 Gal. #6 Fuel | 152,000 |
| Gas | BTU's |
| 1 lb. of Butane | 21,300 |
| 1 Gal. of Butane | 102,600 |
| 1 Cu. Ft. of Butane | 3,260 |
| 1 Cu. Ft. of Manufactured Gas | 530 |
| 1 Cu. Ft. of Mixed Gas | 850 |
| 1 Cu. Ft. of Natural Gas | 1,075 |
| 1 lb. of Propane | 21,600 |
| 1 Gal. of Propane | 91,000 |
| 1 Cu. Ft. of Propane | 2,570 |