The number
At the wholesale diesel price effective 5 August 2026, R26,16 a litre for 500 ppm, a diesel generator produces electricity at roughly R8,50 per kWh once servicing is included. Solar, over the life of the system, lands under R1,00 per kWh.
| Source | Cost per kWh | What that includes |
|---|---|---|
| Diesel generator | ≈ R8,50 | Fuel at R26,16/l plus oil, filters and servicing. Excludes the generator itself. |
| Eskom winter peak (Megaflex) | R7,20 | 720,19 c/kWh, 2026/27, excluding VAT |
| Eskom off-peak (Megaflex) | R1,20 | 120,03 c/kWh, excluding VAT |
| Solar, lifetime | ≈ R0,50 – R0,90 | Installed cost plus maintenance over 25 years of generation |
Diesel: Department of Mineral and Petroleum Resources wholesale price, 0,05% sulphur, effective 5 August 2026. Eskom: Schedule of Standard Prices 2026/27, effective 1 April 2026. Diesel prices change monthly.
Diesel, worked
A generator running at a healthy 70 to 80% load burns about 0,30 litres per kWh. Lightly loaded, it does materially worse.
- Fuel: 0,30 ℓ × R26,16 = R7,85 per kWh
- Oil, filters, servicing and eventual overhaul: R0,50 to R1,00 per kWh
- Total: about R8,35 to R8,85 per kWh, before the generator, tank, bunding and the person who has to start it
Solar, worked
A kWp of panels in Ermelo makes about 1 700 kWh a year. Over 25 years, allowing for gradual panel degradation, that is roughly 40 000 kWh from each kWp.
- Installed cost: R14 000 per kWp
- Operations and maintenance over 25 years: roughly R3 500 per kWp
- R17 500 ÷ 40 000 kWh ≈ R0,44 per kWh, before the cost of capital
- Apply a commercial cost of capital and it lands in the R0,50 to R0,90 band
In one line: every unit moved off a diesel generator and onto solar saves roughly R7,60 to R8,00. Every unit moved off Eskom's winter peak saves about R6,30. Off-peak units are worth far less to displace, which is why your load profile decides the business case.
Where the generator still wins
- A generator delivers on demand, at night, in winter, in the rain. Without storage, an array produces nothing at 03:00.
- Cheap to own, expensive to run. Solar is the reverse. A generator makes sense for a few hours a year, not as a routine supply.
- The crossover is running hours. A set started twice a year is fine. One running several hours most days quietly costs more than the system that would replace it.
For a business with real outage exposure the usual answer is solar for the daytime load, a battery for the critical circuits, and the generator kept for the rare long outage.
Is your generator costing more than you think?
- How many litres did you burn last year? Multiply by about R26. That is the fuel bill alone.
- How much of that ran in daylight? Those units are the ones solar can take over directly.
A business burning 2 000 litres a month spends about R52 000 a month on fuel alone, roughly R628 000 a year, for around 6 700 kWh a month. Moving even half of that onto an array changes the business case entirely.
What does diesel electricity cost per kWh in South Africa?
At the August 2026 wholesale price of R26,16 a litre, a generator produces electricity at roughly R8,35 to R8,85 per kWh once oil, filters and servicing are included, excluding the generator itself.
What does solar electricity cost per kWh?
Spread over 25 years of generation, a commercial solar system lands at roughly R0,50 to R0,90 per kWh including the cost of capital.
Should I get rid of my generator?
Usually not. Keep it for the rare long outage and let solar and a battery carry the daily load. The deciding number is how many hours the generator runs.
Price your generator hours out
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