Africa Estate Farm Tools

Solar system: how big, what it costs, what it saves

For a home, a farm or a business. Pick the town, how the panels lie, your electricity use or bill and your supplier: the panels are sized from that place's own sun in its darkest month, the battery from your night and backup hours, the inverter from your biggest load, and the bill is worked out before and after at the supplier's approved tariff. The example house is there to start; type your own.

1. Where the panels go

Or the farm's own point (decimal degrees)
How the panels lie
Nothing is taken off until you type it. Shade on one panel pulls down the string it is on.

2. Your electricity

I know my

From your bill or prepaid history. The example house is there to start; type your own.

3. Night, backup and the biggest load

Left empty: the hours of dark at this place, 42% in summer to 58% in midwinter (assumes you use power evenly day and night). Type yours from your inverter or meter app.
Add up what runs together: a kettle 2,2, a geyser 3, a borehole pump 1,1 to 2,2. A motor starts at 3 to 7 times its rating for a moment; the inverter's surge rating must carry that.
For outages: lights, fridge, Wi-Fi, a pump. Nothing is added until you type it.
Equipment prices (type your quote)

Median of South African shop prices read on 2026-10-24, VAT included.

Median of four 565 to 615 W panels (R2,38, R2,66, R3,17 and R3,52 a watt): R2,91 a watt; 600 W is the middle of the sizes read.
Median of four 5,12 kWh lithium (LFP) batteries in stock: R10 530 to R14 250.
Median of four 8 kW hybrid inverters in stock: R18 944 to R21 000, R20 250, or R2 531 a kW.
Your installer's figure. Nothing is added until you type it.
Engineering assumptions (change any of them)
Size the panels for
The darkest month: enough sun every month. The average: fewer panels; the grid fills the gap in winter.
PVGIS user manual: "a default value of 14%" for system losses
NREL Annual Technology Baseline 2025, residential battery storage: 85% round-trip efficiency
Datasheets of two 5,12 kWh LFP batteries sold in South Africa: 80% and 90% depth of discharge; the more careful 80% is used
Product page of an 8 kW hybrid inverter sold in South Africa: rated output 8 000 W, maximum PV input 12 800 W

The answer

In Bloemfontein, 14 panels of 600 W (8.4 kWp) facing north cover your use even in June, the darkest month. A 6 kW inverter and 5 batteries of 5.12 kWh carry the night. At this tariff it saves about R 42 172 a year, and pays back in about 2.5 years (the equipment only: installation not added yet).

Panels
14 x 600 W
8.40 kWp
Inverter
6 kW
sized to take the panels' power
Battery
5 x 5.12 kWh
20.5 kWh usable; the longest night needs 19.0 kWh
Saving a year
R 42 172
R 42 862 -> R 690
Equipment cost
R 107 130
R 24 444 + R 15 186 + R 67 500
Payback
2.5 years
equipment only

No installation cost added yet: type your installer's figure.

Check: a complete grid-tied rooftop system under 100 kWp costs R13.50 to R16.50 a watt (GreenCape 2025); this equipment comes to R12.75 a watt before installation, with a battery.

Tariff: Centlec (Mangaung): home, conventional or prepaid, from 2026-07-01. Centlec: NERSA approved MMM (Mangaung) electricity tariffs, 1 July 2026 to 30 June 2027
The fixed charges stay: R 690 a year. Solar saves only on the kWh. Spare power is not paid for here: feeding it back needs your supplier's approval, a meter and an export tariff.

Month by month

Bars: what the panels make. Line: what you use. The darkest month sizes the system.

05001 0001 500Jan: 1 252 kWhFeb: 1 143 kWhMar: 1 261 kWhApr: 1 175 kWhMay: 1 227 kWhJun: 1 170 kWhJul: 1 279 kWhAug: 1 332 kWhSep: 1 361 kWhOct: 1 368 kWhNov: 1 320 kWhDec: 1 299 kWhJanFebMarAprMayJunJulAugSepOctNovDeckWh
Panels makeSizing monthYou use
Ask for a quotePumping cost of a boreholeRead: Irrigation farms in South Africa
The year in a table
MonthSun, kWh per kWp a dayUse kWhPanels makeUsed from the sunSpareBill nowBill with solar
Jan4.818151 252815375R 3 159R 57
Feb4.867361 143736347R 2 841R 57
Mar4.848151 261815375R 3 159R 57
Apr4.667891 175789312R 3 053R 57
May4.718151 227815331R 3 159R 57
Jun *4.649861 17098684R 4 908R 57
Jul *4.911 0191 2791 019157R 5 080R 57
Aug *5.121 0191 3321 019216R 5 080R 57
Sep5.407891 361789501R 3 053R 57
Oct5.258151 368815485R 3 159R 57
Nov5.247891 320789470R 3 053R 57
Dec4.998151 299815423R 3 159R 57
Year10 20515 18710 2054 074R 42 862R 690

* Winter tariff (June to August) where the supplier has one.

What this does not tell you

  • The sun is the average of 2005 to 2023; a cloudy week in any month gives less, and the grid or the battery covers it.
  • Use is the same every day of a season; a farm that pumps or a business that runs machines by day uses more of the sun itself.
  • Spare power is not paid for: feeding it back needs your supplier's approval, a bidirectional meter and an export tariff. On Eskom direct a grid-tied system moves you to a time-of-use tariff (Homeflex for homes).
  • Equipment prices are shop prices on one day; installation, mounting, cabling, protection and the certificate of compliance come from your installer's quote.
  • No price increases, no battery replacement, no panel ageing, no finance cost. Electricity rose 8,76% at Eskom (April 2026) and 9,9% at Centlec (July 2026).
  • Not a design: a registered installer checks the roof, the wiring, the inverter's surge and panel input, and registers the system with Eskom or the municipality.

Sources

Estimate, not advice. Confirm every figure with your bank, attorney and tax practitioner before a decision.