You buy R200 of prepaid electricity and the meter says 73.8 units. What did you just buy?
What a unit is
You buy R200 of prepaid electricity and the meter says 73.8 units. What did you just buy?
A unit of electricity is a kilowatt-hour: one thousand watts running for one hour. Every appliance carries a wattage on its label, and that wattage is simply how fast it uses electricity. A 2,000 watt kettle running for half an hour uses one unit. A 10 watt LED bulb takes a hundred hours to use the same unit. A 3,000 watt geyser element uses one unit every twenty minutes.
The knowhow
So a unit is not a mysterious quantity. It is watts multiplied by hours, divided by a thousand. Once you know that, every appliance in the house becomes a small sum: how much it draws, times how long it runs.
And so
The second thing to know is what you pay for one. The price is on your receipt, but it is easier to work it out: rand paid divided by units received. Eskom's Homelight prepaid rate is R2.71 a unit from April 2026. Municipal customers usually pay a different rate, and yours may include a fixed charge. Your own slip is the only number that matters for you.
Keep this
A unit is a thousand watts for an hour, and your price for one is on your slip.
Now try it with your own numbers. Take your last prepaid receipt, or your last account. Enter the rand you paid and the units you received. The result is your rate, the number every other day this week builds on.
Eskom Distribution, Tariffs and Charges Booklet 2026/27 (Homelight prepaid 271 c/kWh from 1 April 2026). | Definition of the kilowatt-hour: SI derived unit, 1 kWh = 3.6 MJ.
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My tries: every time you save, your numbers, what they came to, and your note are kept here so you can compare later.