Loading the context…
Loading the context…
Power measures the rate of electricity delivery; energy measures an amount delivered or used over time.
Save conceptPower is the rate at which electricity is generated or consumed at a moment. Energy is the accumulated amount over time. Watts, kilowatts, megawatts and gigawatts measure power. Watt-hours and their larger multiples measure energy. A large rated power tells a reader little about duration without a separate energy quantity or fuel and operating information.
One gigawatt equals one thousand megawatts or one billion watts. One gigawatt-hour equals one gigawatt maintained for one hour. For a constant output, energy equals power multiplied by duration. When output changes, total energy adds the amounts delivered during each interval rather than assuming the maximum rating applies continuously.
A storage facility holds 6GWh of usable energy and can discharge at 2GW. Dividing 6GWh by 2GW gives three hours at full output, assuming the usable energy and rating are stated on the same basis. At a constant 1GW, the arithmetic gives six hours. Actual operating restrictions and losses can change the usable amount. These are illustrative figures.
A 2GW power station does not necessarily deliver 2GW every moment. Maintenance, fuel, water and system instructions affect operation. Similarly, a 6GWh storage rating is not the same as 6GW of capacity. Neither measure alone establishes annual electricity production, which also depends on how often the plant operates or recharges.
Eskom seeks partner for proposed 1.5GW Tubatse storage scheme