Ergs
An erg is a unit of energy defined as the work done by a force of one dyne exerted over a distance of one centimeter which is equivelent to 10-7 joules.
Btu (15.8°C, ISO)
The British Thermal Unit (Btu) is a traditional unit of heat, defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. The Btu (15.8°C, ISO) is a specific variant standardized by the International Organization for Standardization (ISO) based on the calorie defined at 15.8°C.