Btu (3.9°C)
The Btu (3.9°C) is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit at the temperature where water reaches its maximum density which occurs at approximately 3.9°C (39°F).
Kilowatt-hours
A kilowatt-hour (kWh) is the amount of energy when a power of one kilowatt (1,000 watts) is used continuously for one hour. Utility companies often bill consumers based on the number of kilowatt-hours consumed.