Bills & sizing
How to read your municipal electricity bill to size solar (2026/27)
Five numbers on a municipal bill size a solar system: monthly kWh over 12 months, your tariff name, the price of your top block, the fixed charges solar cannot remove, and your supply size in amps. A Joburg household on 800 kWh pays R2 865 excl. VAT on City Power’s Prepaid High tariff, of which R420 is fixed — solar attacks the R2 445 energy part, starting with the 379.64 c/kWh top block.
Updated 27 October 2026 · Worked examples use published tariffs; not a formal quote, credit decision or financial advice.
Answer first: A municipal bill is a sizing worksheet in disguise. Pull 12 months of statements (or prepaid token history), find five numbers, and you can brief an installer properly and check whether their system size and savings claim make sense. Water, refuse and property rates on the same account do not change with solar — ignore them. Related: how to read an Eskom bill · prepaid tokens vs solar · sizing tool.
Number 1: kWh per month, over 12 months
Find the electricity section and the consumption line in kWh. Check whether the reading is actual or estimated — estimated months (often marked “E”) are guesses, and a run of them followed by an actual reading produces one huge catch-up month. Add 12 months together and divide by 365 for your daily average. An 800 kWh month is about 26 kWh a day; 600 kWh is 20 kWh a day.
Note the seasonal swing. Highveld homes with electric heating use more in June and July; coastal homes with air-conditioning peak in January and February. Solar output swings too, and the two do not always line up.
Number 2: the tariff name
The tariff decides what each kWh is worth. Common 2026/27 municipal tariffs:
- Cape Town: Home User (R424.30 a month incl. VAT service and wires, then 355.95 c up to 600 kWh and 469.06 c above) or Domestic (R74.77 a month on credit meters, 413.79 c and 493.90 c) (City of Cape Town 2026/27 Annexure 6 tariff book).
- City Power (Joburg): Residential Prepaid High or Low, or conventional; inclining blocks plus basic, service and capacity charges (City of Johannesburg / City Power 2026/27 electricity tariff sheet).
- Tshwane: four inclining blocks from 324.12 c to 445.51 c excl. VAT (NERSA Reasons for Decision, City of Tshwane tariffs FY2026/27).
- eThekwini: a flat 357.47 c/kWh excl. VAT on the main domestic scales (NERSA Reasons for Decision, eThekwini tariffs FY2026/27).
If the bill only shows a scale number or code, the municipal tariff book translates it. Eskom-direct customers see Homepower, Homeflex or Homelight instead — Homeflex vs Homepower.
Number 3: the price of your top block
Inclining-block tariffs charge more for each extra kWh. Solar and batteries remove your most expensive kWh first, so that is the price to value savings at. City Power’s own 2026/27 worked bill for Prepaid High at 800 kWh shows it clearly (City of Johannesburg / City Power 2026/27 electricity tariff sheet):
| Line (excl. VAT) | kWh | Rate | Rand |
|---|---|---|---|
| Block 1 (0–350) | 350 | 290.46 c | R1 016.61 |
| Block 2 (351–500) | 150 | 333.18 c | R499.77 |
| Block 3 (above 500) | 300 | 379.64 c | R1 138.92 |
| Basic charge | R210.00 | ||
| Service charge | R70.00 | ||
| Capacity charge | R140.00 | ||
| Total | 800 | avg 358.16 c | R2 865.30 |
The average is 358.16 c, but the first 300 kWh of solar each month are worth 379.64 c excl. (436.59 c incl. VAT), and the next 150 are worth 333.18 c. An installer who values your savings at the average undersells the system; one who values every kWh at the top block oversells it.
Number 4: the fixed charges solar will not touch
Add up every rand amount that does not move with kWh: basic, service, capacity, network, wires, AMI or meter fees. In the Joburg example that is R420 a month excl. VAT. In Cape Town on Home User it is R424.30 incl. VAT; the City’s own example shows the charge stays even at 0 kWh (City of Cape Town cost-of-electricity page). Registering a solar system adds lines in some metros — Tshwane charges domestic SSEG customers R324 a month excl. VAT and eThekwini R76.83 per inverter kVA — so put those in too. Your realistic maximum saving is the energy part of the bill, never the total — fixed charges with solar · why the bill is still high after solar.
Number 5: your supply size
The bill, the meter box or the main breaker shows the supply in amps (60 A, 80 A) or kVA, and single- or three-phase. It caps how large an inverter you can connect and how much you are allowed to export, and it decides whether an EV charger fits alongside — maximum solar kW · single vs three phase.
Turn the five numbers into a system
- Panels: divide daily kWh by your city’s yield. PVGIS gives about 4.8 kWh per kWp per day in Johannesburg, 4.7 in Pretoria, 4.6 in Cape Town (2.8 in June) and 4.0 in Durban for a north-facing 25° array (EU JRC PVGIS v5.2 (1 kWp, 25° north-facing, 14% system loss; run 27 Oct 2026)). The 26 kWh-a-day Joburg home needs about 5.5 kWp.
- Battery: estimate evening and night kWh — usually 40–50% of the daily total in a working household. If you are too busy to work it out — get a 16 kWh battery that can be expanded later. It covers a typical evening with an outage reserve and sits in the best rand-per-usable-kWh band — battery sizing.
- Inverter: add the loads that run together (kettle, microwave, pool pump, borehole). Most homes on an 800 kWh bill land on a 5 kW hybrid; homes with an EV or three-phase supply step up — inverter size.
- Savings: value self-used solar at your top block, then the next block down; subtract any new SSEG fixed line; add export at the metro credit rate.
For the Joburg 800 kWh example: replacing 450 kWh a month removes the 300 kWh at 379.64 c and 150 kWh at 333.18 c — R1 638.69 excl., about R1 885 incl. VAT a month. That matches the band in our R3 000 bill answer.
Bill red flags to fix before you size
- Three or more estimated readings in a row — ask for an actual reading first.
- A tariff that does not match your house (a business tariff on a home, or Lifeline on a large house).
- Arrears or interest lines inflating the total — they are not consumption.
- Sudden kWh jumps with no new appliance — check for an earth-leakage fault, a stuck geyser element or a faulty meter before sizing solar around it.
Bottom line
Twelve months of kWh, the tariff name, the top-block price, the fixed charges and the supply size are all you need. Put them on a one-page brief, send the same brief to three installers, and check every savings claim against your own top block — how to read a solar quote · Tshwane 2026/27 payback · eThekwini 2026/27 payback.
Quick questions
What is the most important number on my electricity bill for solar?
Your monthly kWh, averaged over 12 months. Divide the annual total by 365 to get daily kWh, which sets panel and battery size. The second most important is the price of your top block, because solar removes those kWh first.
Will solar remove my fixed charges?
No. Service, network, capacity and basic charges stay on the bill whether you use grid energy or not. City Power’s Prepaid High tariff, for example, carries R420 a month excl. VAT of fixed charges in 2026/27.
How many panels do I need for an 800 kWh a month bill?
About 26 kWh a day in Johannesburg needs roughly 5.5 kWp of panels, because PVGIS models about 4.8 kWh per kWp per day there. Ten 550 W panels on a 5 kW hybrid with a 16 kWh battery is the standard fit.
I am on prepaid. Where do I find my usage?
Your token slips and the vending app or retailer history show kWh bought per purchase. Add 12 months of purchases to get annual kWh, or ask the municipality for a vending history.