South African electricity, term by term
The words that come up in every load shedding briefing and Eskom system status report, defined plainly, with the live numbers behind them where this site measures them.
Load shedding (MLR)
Manual Load Reduction: Eskom instructs municipalities to switch off blocks of demand on a rotating schedule. This is the outage the public experiences. Since April 2022 it has removed 27 082 GWh from the grid; 2026 has seen none so far. One stage is roughly 1 000 MW.
Interruptible load (ILS)
Large industrial customers, mainly smelters, take a cheaper tariff in exchange for being cut at short notice. Eskom uses it on ordinary evenings to shave the peak. It is demand management, not load shedding, and this site reports it separately.
UCLF
Unplanned Capability Loss Factor: the share of capacity offline because plant is broken, the number behind most load shedding. This site shows it as MW of breakdowns; the 12-month average is about 9 406 MW.
PCLF
Planned Capability Loss Factor: capacity offline for scheduled maintenance. High PCLF in summer is healthy; high UCLF any time is not.
EAF
Energy Availability Factor: the share of the fleet actually available to run, roughly 100% minus planned and unplanned losses. Eskom's recovery since 2023 is a story of EAF climbing out of the low 50s.
OCGT / diesel peakers
Open-cycle gas turbines burning diesel, run for the evening peak and emergencies. Expensive, so heavy use signals strain. Record hour in this dataset: 3 133 MW.
Pumped storage
The grid's batteries: Ingula, Drakensberg, Palmiet and Steenbras pump water uphill overnight and generate at the peaks. Pumping shows below zero on the dashboard stack.
RSA contracted demand
The national demand Eskom must serve, the dark line on the dashboard. Latest hour: 19 574 MW.
Residual demand
Contracted demand minus wind and solar output: what the dispatchable fleet must cover. As renewables grow, residual demand gets spikier even when demand does not.
Carbon intensity
Grams of CO₂ per kilowatt-hour generated. South Africa averages about 830 g/kWh against a world average of 458. Full method on the carbon intensity page.
CSP
Concentrated solar power: mirrors heat molten salt, which stores energy and keeps generating after sunset, unlike photovoltaic panels. South Africa has seven plants, all in the Northern Cape.
Nameplate capacity
What a station could produce flat out, in MW. Capacity is not output: a wind farm produces perhaps a third of its nameplate over a year, a nuclear plant most of it.
Capacity factor
Energy actually produced divided by what nameplate capacity could have produced. The honest way to compare technologies that run at different rhythms.
SAPP imports
Power bought through the Southern African Power Pool, mostly Cahora Bassa hydropower from Mozambique, usually one to two thousand MW.
SAWEM
The South African Wholesale Electricity Market, being introduced as the sector unbundles, with the NTCSA as market operator. See the SAWEM page for the data side.
Definitions reflect how the figures are used on this site, calculated from data Eskom publishes. Corrections are welcome through the contact form on the main page.