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)
2. Your electricity
From your bill or prepaid history. The example house is there to start; type your own.
3. Night, backup and the biggest load
Equipment prices (type your quote)
Median of South African shop prices read on 2026-10-24, VAT included.
Engineering assumptions (change any of them)
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).
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.
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.
The year in a table
| Month | Sun, kWh per kWp a day | Use kWh | Panels make | Used from the sun | Spare | Bill now | Bill with solar |
|---|---|---|---|---|---|---|---|
| Jan | 4.81 | 815 | 1 252 | 815 | 375 | R 3 159 | R 57 |
| Feb | 4.86 | 736 | 1 143 | 736 | 347 | R 2 841 | R 57 |
| Mar | 4.84 | 815 | 1 261 | 815 | 375 | R 3 159 | R 57 |
| Apr | 4.66 | 789 | 1 175 | 789 | 312 | R 3 053 | R 57 |
| May | 4.71 | 815 | 1 227 | 815 | 331 | R 3 159 | R 57 |
| Jun * | 4.64 | 986 | 1 170 | 986 | 84 | R 4 908 | R 57 |
| Jul * | 4.91 | 1 019 | 1 279 | 1 019 | 157 | R 5 080 | R 57 |
| Aug * | 5.12 | 1 019 | 1 332 | 1 019 | 216 | R 5 080 | R 57 |
| Sep | 5.40 | 789 | 1 361 | 789 | 501 | R 3 053 | R 57 |
| Oct | 5.25 | 815 | 1 368 | 815 | 485 | R 3 159 | R 57 |
| Nov | 5.24 | 789 | 1 320 | 789 | 470 | R 3 053 | R 57 |
| Dec | 4.99 | 815 | 1 299 | 815 | 423 | R 3 159 | R 57 |
| Year | 10 205 | 15 187 | 10 205 | 4 074 | R 42 862 | R 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
- PVGIS 5.3, European Commission Joint Research Centre (PVGIS-SARAH3, 2005 to 2023): daily yield of 1 kWp per month, per town (read 2026-10-24)
- NASA POWER climatology (sun on flat ground), the cross-check on PVGIS (read 2026-10-24)
- Centlec: NERSA approved MMM (Mangaung) electricity tariffs, 1 July 2026 to 30 June 2027 (effective 2026-07-01)
- Moqhaka Local Municipality: final tariff schedule 2025/26 (section 13, electricity), plus the 9,01% increase in its 2026/27 budget (effective 2026-07-01)
- Moqhaka Local Municipality, narrated draft annual budget 2026/27: electricity increase 9,01% (2026-05)
- Eskom Tariffs and Charges Booklet 2026/2027 (NERSA approved, non-local authority) (effective 2026-04-01)
- PVGIS user manual: "a default value of 14%" for system losses
- NREL Annual Technology Baseline 2025, residential battery storage: 85% round-trip efficiency
- Duffie and Beckman, Solar Engineering of Thermal Processes: day length from latitude and date (eq. 1.6.10)
- Equipment: median of South African solar shops' listed prices, VAT included (read 2026-10-24)
- GreenCape, Energy Services Market Intelligence Report 2025, Table 4: benchmarks for embedded PV 2024/25 (2025-04)
- Town coordinates: GeoNames gazetteer (CC BY 4.0)
Estimate, not advice. Confirm every figure with your bank, attorney and tax practitioner before a decision.