What is solar payback period?
Solar payback period is how many years it takes for your electricity savings to equal what you spent on the system. After payback, every rand of savings is profit — for 20+ years.
The formula is simple:
Payback years = System cost ÷ Annual electricity savings
But the inputs depend heavily on where you live — your tariff, how much sun you get, and your bill size.
South Africa's solar advantage
South Africa has some of the best solar irradiance in the world. The Northern Cape receives over 2,000 kWh per kWp per year — comparable to the Middle East. Even coastal cities like Cape Town and Durban beat European solar farms.
Combined with Eskom tariffs that have risen 600% since 2010 and are projected to keep climbing, the economics are compelling.
Payback period by city (2026)
| City | Tariff (R/kWh) | PVGIS yield | 3 kW payback (no battery) | 3 kW payback (with battery) |
|---|---|---|---|---|
| Cape Town | R3.21 | 1,780 kWh/kWp | 5.2 years | 4.1 years |
| Johannesburg | R3.08 | 1,820 kWh/kWp | 5.0 years | 3.9 years |
| Pretoria | R2.94 | 1,840 kWh/kWp | 5.3 years | 4.2 years |
| Durban | R2.98 | 1,750 kWh/kWp | 5.6 years | 4.4 years |
| Bloemfontein | R2.71 | 1,920 kWh/kWp | 5.5 years | 4.3 years |
| Kimberley | R2.76 | 1,950 kWh/kWp | 5.3 years | 4.2 years |
| Upington | R2.76 | 2,050 kWh/kWp | 5.0 years | 4.0 years |
| Polokwane | R2.76 | 1,870 kWh/kWp | 5.6 years | 4.4 years |
| Port Elizabeth | R2.76 | 1,790 kWh/kWp | 5.9 years | 4.6 years |
| Sandton | R3.08 | 1,820 kWh/kWp | 5.0 years | 3.9 years |
Based on a 3 kW system at R55,000 installed, R500/month bill, 0.80 loss factor. Battery scenario assumes 85% self-consumption vs 60% without battery.
What affects payback period most?
- Your electricity tariff. Higher tariff = faster payback. Cape Town (City of Cape Town, R3.21/kWh) has the highest residential tariff in SA, which is why it has the best payback despite not having the most sun.
- Your bill size. A R4,000/month bill has far more room to offset than a R800/month bill. Systems sized for high bills have proportionally better ROI.
- Battery or not. Adding a battery costs R30,000–R80,000 more but raises self-consumption from ~60% to ~85%. The maths only works if you have frequent load-shedding or a high daytime bill.
- Quality of installation. A badly installed system with poor shading analysis or undersized cables can lose 20–30% of yield, wrecking your payback calculation.
25-year saving projection
Payback period is only part of the story. The real question is: how much will I save over the system's lifetime?
Assuming 12% annual tariff escalation (the Eskom MYPD average), a Cape Town homeowner with a R3,000/month bill could save over R1.4 million over 25 years from a R75,000 system investment.
Get your personalised payback calculation
Use our free solar calculator to get a city-specific payback period based on your exact bill size and whether you want battery backup.