BTU (International) (BTU)
The British Thermal Unit (BTU), symbolized as BTU, is an imperial unit of energy used to measure heat. One BTU is the heat needed to raise one pound of water by 1°F. The BTU originated in the 19th century, during the Industrial Revolution, for heating in the UK and the US. It is still used in HVAC systems and energy production. The BTU connects imperial and metric energy systems, especially in countries that use imperial units for industry.
Kilowatt Hour (kWh)
The kilowatt-hour, symbolized as kWh, is a common unit in electricity billing and energy reporting. It is the energy used by a 1-kilowatt device for 1 hour, or 3.6 million joules. With the advent of electrification in the late 1800s and early 1900s, the kilowatt-hour made measuring electrical energy simpler for both utilities and customers. Its use is crucial for billing, energy management, and understanding electricity use in homes, industry, and renewable energy.