If you buy prepaid electricity in Zimbabwe, you've noticed the pattern: the token you buy at the start of the month gives you a healthy pile of units, and the token you buy in week three — same money — gives you noticeably fewer. That's not the agent skimming you and it's not a glitch. It's ZETDC's stepped tariff working exactly as designed. I built VoltZW, a free ZESA token calculator, around that exact tariff structure, so here's the full breakdown of how the maths works — with the actual band rates the calculator uses.
What a stepped (inclining block) tariff is
ZETDC doesn't charge one flat price per kilowatt-hour. Instead, your consumption in each calendar month is split into bands, and each band has its own rate. The first 50 units you buy in a month are the cheapest. The next 50 cost a bit more. From unit 101 the price jumps sharply, and it keeps climbing until unit 400 — after which everything is charged at the top rate. Regulators call this an inclining block tariff; the idea is to keep a basic amount of electricity affordable for low-usage households while charging heavy users closer to the real cost of supply.
Crucially, the meter tracks your cumulative purchases for the month. The bands don't reset when you buy a new token — they reset on the 1st of the month. That single fact explains almost every "why did I get so few units?" complaint.
The current band rates (as used by VoltZW)
These are the ZERA-approved ZETDC domestic rates that the VoltZW calculator currently uses (effective 7 July 2026, billed in ZWG). The "you pay" column includes the 6% REA levy, which is added to every purchase. US$ figures are approximate at ≈28.4 ZWG per US$1.
| Monthly band | Base ZWG/kWh | You pay (incl. 6% levy) | ≈ US$/kWh |
|---|---|---|---|
| First 50 units | 2.1437 | 2.2723 | 0.08 |
| 51 – 100 units | 2.4117 | 2.5564 | 0.09 |
| 101 – 200 units | 4.2874 | 4.5447 | 0.16 |
| 201 – 300 units | 6.1632 | 6.5330 | 0.23 |
| 301 – 400 units | 6.6991 | 7.1011 | 0.25 |
| Above 400 units | 6.9671 | 7.3851 | 0.26 |
Look at the jump from band two to band three: ZWG 2.5564 to ZWG 4.5447 per unit — a 78% increase the moment you cross 100 units in a month. That cliff is where most households' "cheap electricity" quietly ends. Tariffs do change (rates are periodically reviewed by ZERA), so treat the calculator as the living reference rather than any screenshot of this table.
A worked example: ZWG 500, twice in one month
Say it's the 2nd of the month and you buy a ZWG 500 token on a fresh meter. The maths walks down the bands:
- First 50 units at 2.2723 = ZWG 113.62 — leaving ZWG 386.38
- Next 50 units (51–100) at 2.5564 = ZWG 127.82 — leaving ZWG 258.57
- Band 101–200 at 4.5447: ZWG 258.57 buys 56.9 more units
Total: ≈156.9 kWh for ZWG 500.
Two weeks later you're running low and buy another ZWG 500. But now the meter knows you've already taken 156.9 units this month, so this token starts deep in band three:
- Rest of band 101–200 (43.1 units) at 4.5447 = ZWG 195.88 — leaving ZWG 304.12
- Band 201–300 at 6.5330: ZWG 304.12 buys 46.6 more units
Total: ≈89.7 kWh for the same ZWG 500 — about 43% fewer units than the identical purchase two weeks earlier. Nothing went wrong; you simply climbed the staircase. The effect is even starker in USD terms: US$10 (≈ZWG 284) buys about 109 units on a fresh meter, but only about 40 units if you've already bought 300 that month.
What this means for how you buy
Splitting purchases inside a month changes nothing. Because the bands are cumulative, ten ZWG 50 tokens cost exactly the same as one ZWG 500 token. Don't waste trips to the agent chasing a discount that doesn't exist.
The month boundary is the only lever. The bands reset on the 1st. If it's the 29th and you've used 380 of your 400 discounted units, topping up heavily now puts everything at the top rate — while the same purchase on the 1st starts back at ZWG 2.2723 per unit. If you can shift a big top-up across the boundary, do it.
Know where you are on the staircase. The single most useful number is "units already bought this month". Punch it into the ZESA token calculator along with what you want to spend, and it shows exactly which bands your money lands in, how many kWh you'll get, and what buying your remaining discounted quota would cost — in ZWG or US$.
Why I built the calculator this way
Most "ZESA calculators" floating around are a flat rate multiplied by your amount — which is wrong for everyone except a household that never crosses 50 units. VoltZW implements the actual band-walking logic: it takes your spend, subtracts each band's cost as it fills, and reports the per-band breakdown so you can see why you got the number you got. It also handles the reverse direction (units → cost) and tracks the 400 kWh monthly discounted quota. Cross-checking against published tariff schedules from Zimbabwean price trackers is how the rates stay honest — when ZERA approves a new schedule, the calculator gets updated, this article doesn't.