Carbon-Pros Analyst Blog

Electric power is the rate at which electricity does work. This is measured at a single point in time so it has no time dimension. The unit of measure for electric power is a watt (W). Watts are usually billed in blocks of a thousand known as a kilowatt (kW). The maximum amount of electric power that a piece of equipment can accommodate is the capacity of that equipment. Power plants are rated based on their maximum capacity, usually in megawatts (MW) or gigawatts (GW).

Electric energy is the amount of work that can be done by electricity. The unit of measure for electric energy is a watthour (Wh) with billing usually in blocks of one thousand known as a kilowatthour (kWh = 1,000 Wh). Electric energy is measured over a period of time and therefore has both energy and time dimensions. The amount of electric energy produced or used during a specified period of time by a piece of electrical equipment is referred to as generation or consumption. Larger units of work can be expressed as megawatthours (MWh = 1,000 kWh) or gigawatthours (GWh = 1,000 MWh). A large-scale unit of work used by national reporting agencies is terawatt-year (TWyr).

Energy units can be converted from one type of energy to another. For example, the energy in electric power can be converted to the energy in heat. Utilities usually bill natural gas consumption in therms. A therm is a unit of heat equal to 100,000 British thermal units (BTU). It is approximately the energy equivalent of burning 100 cubic feet of natural gas. National reporting agencies often report total energy consumption in quadrillions of BTUs or quads.