When Is the Best Time to Buy Prepaid Electricity in South Africa?
The best time to buy prepaid electricity depends on who supplies your power. On municipal block tariffs like City Power in Johannesburg, buying early in the month can keep you in the cheaper block. On Eskom Homelight or eThekwini in Durban, both flat-rate suppliers, the date makes no difference to your price per unit at all.
What "best time to buy" actually means
Most people who ask about the best time to buy prepaid electricity have heard that buying early in the month saves money. That advice is only half true, and it depends entirely on who bills you.
An inclining block tariff (IBT) splits your monthly usage into bands. The first band is the cheapest. Once your month-to-date usage crosses into the next band, every extra unit costs more. Your usage total resets to zero on the 1st of each calendar month, regardless of when you actually buy tokens.
Some suppliers, including Eskom's Homelight tariff and eThekwini in Durban, have moved away from blocks entirely and now charge one flat rate per kWh. On those, this whole strategy has no effect on your bill. We cover exactly which suppliers use blocks and which don't in the city-by-city guide below.
Does your municipality use block tariffs?
Here's how the main South African suppliers compare as of the 2026/27 tariff year. Rates include VAT and are rounded. Fixed monthly charges are shown separately, because several suppliers deduct these from your first purchase of the month.
| Supplier | Tariff type | Rate per kWh (incl. VAT) | Fixed monthly charge |
|---|---|---|---|
| Eskom Homelight 20A (direct) | Flat, no blocks | ± R2.70 | None |
| Eskom Homelight 60A (direct) | Flat, no blocks | ± R3.44 | None |
| City Power (Johannesburg) | Block tariff | R3.34 – R4.37 | R241.50 |
| City of Cape Town | Block tariff | R4.14 – R4.94 | ± R74.77 |
| eThekwini (Durban) | Flat, no blocks | ± R4.17 | None (most residential) |
| Tshwane (Pretoria) | Block tariff | ± R3.40 – R4.70* | Varies by connection |
| Ekurhuleni | Block tariff (steep top block) | ± R2.97, rising sharply above 600–700 kWh* | Varies by connection |
Last updated: 01 September 2026. *Tshwane and Ekurhuleni figures are indicative and should be confirmed on your municipal account, since block boundaries and rates are updated annually and can differ by connection size. See our full electricity cost breakdown for South Africa for more detail on how these numbers are built up.
How far does R500 actually go?
A flat R500 buys a very different amount of electricity depending on who bills you, mostly because of fixed fees and which block you land in.
| Supplier | R500 buys roughly | Why |
|---|---|---|
| Eskom Homelight 20A | ± 185 kWh | Flat rate, no fixed fee deducted |
| eThekwini (Durban) | ± 120 kWh | Flat rate, no fixed fee deducted |
| Cape Town (Block 1) | ± 100–105 kWh | ± R74.77 fixed fee comes off first |
| City Power (Block 1) | ± 75–80 kWh | R241.50 fixed fee comes off first |
Notice the pattern: it's the fixed monthly fee, not the per-kWh rate, that shrinks a City Power or Cape Town purchase the most. On a flat-rate supplier, R500 simply divides by the rate with nothing subtracted first.
The City Power trap: why a small top-up can buy you nothing
This is the part most articles about "buying early" leave out, and it's the one that actually costs Joburg households the most money. City Power's Residential Prepaid High tariff, the default for almost every home meter, carries a fixed service and network charge. From 1 July 2026, that charge is R241.50 a month, including VAT.
Here's the catch. The fee isn't billed separately. It's taken straight out of your first token purchase of the month, before you receive a single unit of electricity. So if a Joburg household tops up with R200 on the 1st, expecting an early, cheap start to the month, they get 0.00 kWh. The full R200 goes toward the fixed fee, and they're still R41.50 short.
Real savings example: early buyer vs late buyer
Take a household on City Power using 500 kWh in a month. If they buy in small amounts throughout the month and only top up when the meter is nearly empty, a large share of their usage ends up priced in the higher blocks, closer to R4.00 to R4.37 a kWh.
If the same household buys a large enough amount early in the month, once the R241.50 fixed fee is covered, more of their 500 kWh sits in the cheaper R3.34 to R3.70 range before crossing into the top block. On 500 kWh, that gap between "mostly cheap blocks" and "mostly expensive blocks" can run to a few hundred Rand over a month.
As an accountant by training, the number that matters to me isn't the headline rate, it's the blended rate you actually pay once fixed charges and block creep are added in. Two households using identical electricity can pay noticeably different totals purely because of when and how they bought their tokens.
Does this trick work on Eskom direct supply?
If Eskom bills you directly, meaning there's no municipality in between, you're most likely on Homelight, Homepower, or Homeflex. Homelight no longer uses an inclining block structure at all. Every kWh costs the same flat rate, whether it's your first unit of the month or your five-hundredth.
Homepower works differently again: it has a flat energy rate plus a fairly large fixed monthly charge (roughly R536 in 2026), but that charge isn't tied to your first token purchase the way City Power's is, so there's no "buy early" trap to worry about.
Homeflex is the one Eskom tariff where timing genuinely matters, but not by date. It's a time-of-use tariff, covered in the next section.
City-by-city quick guide
Johannesburg (City Power)
Buy early, and buy enough to clear the R241.50 fixed fee in one purchase. Check your month-to-date usage on City Power's self-service portal if you're not sure which block you're in.
Cape Town
Cape Town's Domestic tariff also uses blocks, with a much smaller fixed charge of around R74.77 a month. The same early-purchase logic applies, though the fixed-fee trap is far less severe here than on City Power.
Durban (eThekwini)
Timing doesn't matter. eThekwini charges a flat rate, currently around R4.17 a kWh, to nearly all residential prepaid customers, with no fixed monthly charge and no blocks to worry about.
Tshwane and Ekurhuleni
Both still use block structures, and Ekurhuleni's top block in particular can jump sharply once you pass 600 to 700 kWh in a month. Confirm your exact block boundaries on your municipal account, since these are reviewed every financial year.
Time-of-use tariffs: a different kind of "best time"
If you're on Eskom Homeflex, or a municipal time-of-use tariff, forget the calendar and watch the clock instead. Homeflex's winter peak rate (June to August, weekdays 06:00 to 09:00 and 17:00 to 20:00) runs to around R8.47 a kWh, compared with roughly R1.91 a kWh off-peak.
The practical move on a time-of-use tariff is shifting big loads, geysers, pool pumps, tumble dryers, away from those peak windows rather than worrying about which day you top up. This matters even more during winter, when many households are also managing load shedding schedules on top of peak pricing.
Practical rules for buying prepaid electricity
- Confirm your tariff type. Look at a recent statement or your municipal account to see if you're on a block tariff or a flat rate.
- On block tariffs: buy early in the month, and buy enough in one purchase to clear any fixed fee plus a reasonable chunk of usage.
- On flat-rate tariffs (Eskom Homelight, eThekwini): buy whenever suits you. There's no cost benefit to timing it.
- On time-of-use tariffs (Homeflex): shift heavy appliance use out of peak hours rather than chasing a "best day."
- Track your usage with your municipality's app so you know which block you're heading into before you buy.
- Re-check rates every July. Most municipal tariff years run 1 July to 30 June, and Eskom's own year runs 1 April to 31 March, so your numbers shift twice a year.
The way to make this question irrelevant
Timing your prepaid purchases can save a real household a few hundred Rand a year. Cutting how much grid electricity you buy in the first place saves a lot more, especially once you're generating power during the exact hours your geyser, stove, and aircon are running.
If you're weighing that decision, start with real numbers rather than marketing claims. Our solar panel prices in South Africa guide breaks down current cost per watt, and our solar buying guide walks through system sizing without the sales pressure. If load shedding is your bigger concern, our home inverter price guide and solar battery price guide cover backup power on its own, separate from full solar generation. For households wanting to cut grid reliance further, our off-grid solar system guide explains what that actually costs and requires.
Frequently Asked Questions About Buying Prepaid Electricity in South Africa
The best time depends on your supplier. If you're on a municipal block tariff, like City Power in Johannesburg or Cape Town, buying early in the month keeps more of your usage in the cheaper first block. If you're on Eskom Homelight or eThekwini in Durban, timing makes no difference at all, because both charge one flat rate for every unit.
There's no direct discount, but there can be an indirect saving on block-tariff municipalities. Buying early means more of your month's usage falls into the cheapest block before you cross into pricier ones. On flat-rate suppliers like Eskom Homelight or eThekwini, the 1st of the month has no effect on your rate.
No, not for Homelight customers. Since April 2025, Eskom Homelight 20A and 60A charge a single flat rate per kWh with no blocks, so a unit bought on the 2nd costs exactly the same as a unit bought on the 28th. Homeflex customers are the exception, because that tariff charges different rates by time of day, not by date.
On a block-tariff municipality like City Power, buying a large amount on the 30th, near month-end when you've already used a lot, means most of it lands in the top block, which can be R1 or more per kWh pricier than the first block. On a flat-rate supplier like Eskom Homelight or eThekwini, there's no difference at all between the 30th and the 1st.
It isn't automatically cheaper, but on municipalities that use inclining block tariffs, your usage total resets to zero on the 1st of each calendar month. Topping up early means your first kWh of the new month fall into the lowest-priced block again, rather than continuing at whatever high block you ended the previous month on.
On block-tariff municipalities, electricity is most expensive once your monthly usage crosses into the top block, often after 600 to 700 kWh. On time-of-use tariffs like Eskom Homeflex, electricity is most expensive during winter weekday peak hours (06:00 to 09:00 and 17:00 to 20:00), when the rate can be more than four times the off-peak price.
In Durban, timing doesn't matter. eThekwini charges a single flat rate per kWh for nearly all residential prepaid customers, with no block structure, so buying on the 1st, the 15th, or the 30th costs exactly the same per unit.
Not necessarily, and on City Power in Johannesburg you can actually get zero units from your first small purchase. City Power deducts its fixed monthly service and network charge, currently R241.50, from your first token of each month before any electricity is issued, so a top-up under that amount buys you nothing until the fee is cleared.
For most block-tariff municipalities, the first few days of the month are best, once you've cleared any fixed monthly fee. Buy a large enough amount to cover the fixed charge plus a decent chunk of Block 1 usage, rather than small top-ups that get eaten by the fee.
Only if you buy it early in the month on a block-tariff supplier. A large purchase made on the 28th still gets priced against whatever block you're already in, so a big top-up late in the month doesn't reset you back to the cheap rate.
No. Block tariffs reset automatically on the 1st of each calendar month based on the date, not on when or how much you buy. There is no way to manually reset your block partway through the month.
Check your municipality's official app or customer portal, such as the City of Cape Town's online services or Joburg's City Power self-service portal, which show your month-to-date usage. You can also estimate it yourself by adding up your token purchases for the current calendar month.
No. It only helps households on municipal block tariffs, such as City Power (Johannesburg), Cape Town, Tshwane, and Ekurhuleni. If you're on Eskom Homelight or eThekwini's flat rate, there's no block to game, so this timing trick makes no difference to your bill. For a wider view of what drives your bill, see our guide to electricity costs in South Africa.
Solar reduces how many grid units you need to buy in the first place, which shrinks or removes your exposure to the expensive top blocks. It doesn't change how the tariff works, but if you're generating a good share of your own daytime power, the block you land in each month matters a lot less. See our solar buying guide for how to size a system around your usage.
On Eskom Homelight, R500 buys around 185 kWh, and on eThekwini's flat rate it buys around 120 kWh, since neither deducts a fixed fee first. On City Power or Cape Town, expect closer to 75 to 105 kWh, because the fixed monthly service charge comes off your first purchase before any electricity is issued.
The geyser is usually the biggest single drain, often 30 to 40 percent of a household's electricity, so turning the thermostat down to around 55 to 60°C and fitting a geyser blanket makes the biggest dent. After that, shifting big loads like the geyser, stove, and tumble dryer away from Homeflex peak hours, and switching to LED lighting, stretches a token further without changing your lifestyle much. A solar water heater removes the geyser cost almost entirely.
On block-tariff suppliers, the cheapest approach is one larger purchase early in the month rather than several small top-ups, since that avoids repeatedly losing fixed fees and keeps more usage in the low block. On flat-rate suppliers like Eskom Homelight or eThekwini, there's no cheaper way to buy, only a cheaper way to use less overall, such as reducing geyser and appliance consumption.
For standard flat-rate and block tariffs, the day of the week makes no difference at all, only the calendar date and your month-to-date usage matter. Day-of-week pricing only exists on certain time-of-use tariffs, and even then it's the time of day, not the day itself, that changes the rate.
On standard flat and block tariffs, the time of day makes no difference, every kWh costs the same whether it's used at 2pm or 2am. On Eskom's Homeflex time-of-use tariff, off-peak hours are cheapest at around R1.91/kWh, while winter weekday peak hours (06:00 to 09:00 and 17:00 to 20:00) can cost more than four times that.
In Cape Town, the first few days of the month are best, since the city still uses a block tariff and your usage resets on the 1st. The fixed fee here is smaller than City Power's, around R74.77, so the early-purchase benefit is more about staying in Block 1 than avoiding a big fee deduction.
Alternative Energy Sources is not affiliated with any solar installer, panel brand, battery manufacturer, or Eskom. Prices, tariffs, and load shedding stages change often. Always confirm current figures with your municipality, Eskom, or the relevant official source (such as NERSA) before making a buying decision.