SolarPowerGuide
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How Heatwaves Affect Solar Panel Performance in South Africa – 2025 Data

Panels lose efficiency above 25 °C, but South Africa’s intense sunlight more than makes up for it – here are the real numbers.

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Do Solar Panels Struggle in South African Heatwaves?

Short answer: No — they usually produce more power

Real 2025 data from Gauteng, Western Cape & beyond

The Temperature Coefficient Explained

Most panels lose -0.34% to -0.39% of their rated power for every °C above 25 °C.

At 70–75 °C [Panel Temp] (common in SA summers) → up to 18–19 % loss

-0.35%/°C

Average in South Africa

Real Panel Temperatures in SA Heatwaves

Ambient Temp Panel Temp Power Loss
30 °C50–55 °C8–11 %
35 °C60–65 °C12–15 %
40 °C70–75 °C16–19 %
45 °C (extreme)80+ °C20–23 %

Why Production Still Stays High

  • Heatwaves = cloudless skies → irradiance often 1,100–1,200 W/m²
  • Extra sunlight easily outweighs the temperature loss
  • Real systems regularly hit 90–105 % of rated power on 40 °C+ days

Live Example – Pretoria 41 °C Day (Jan 2025)

72 °C

Panel temperature

1,150 W/m²

Irradiance

7.4 kW

from 8 kW system → 93 %

How to Minimise Heat Losses

Leave 100–150 mm gap under panels

Use light-coloured or reflective roof paint

Choose N-type panels (≤ -0.30 %/°C)

Mount slightly raised on tilted racks

Bottom Line for 2025

Yes — panels lose efficiency in extreme heat.

But South Africa’s intense summer sun more than compensates.

On most 40 °C+ days you’ll still get 90–100 % (often more) of rated output.