Btu (15.8°C, Canada)
The Btu (15.8°C, Canada) is a variant of the British thermal unit defined as the energy to raise the temperature of one pound of water by one degree Fahrenheit at a starting temperature of 15.8°C. This definition is tailored to Canadian standards reflecting the country's historical reliance on both imperial and metric.
Btu (I.T.)
The British Thermal Unit (International Table) is a unit of energy commonly used in the United States defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit at a constant pressure of one atmosphere.