Always On Energy - Inverter power output degrading due to high summer ambient temperature.

☀️ Oversizing the Inverter to prevent Under performance in Summer.

Designing solar systems should always be with sunlight and summer ambient temperature in mind.

Let’s talk "temperature derating"—the inverter performance killer.

🔍 Most Solar Inverters optimal power outputs lab benchmark are at 25°C ambient temp. But Johannesburg regularly hits 35–38°C.

Here’s the catch: 

➡️ Mostly Inverters are designed to have a temperature rise of 40 deg C from 25 deg C to 65 deg C for full power output. 

➡️ At a 38°C ambient,  the ambient alone  reduces the rise in temperature due to max Power output, by 13 deg C (38-25). Thus there is 27 deg temp rise left and 27/40 is 67.5% of max power output. What ever the Inverter size is it can reduce to 67.5% in Johannesburg. In a 10kW load requirement in Johannesburg, based only on summer ambient temperature, the actual Inverter size should  now be 10/0.675 = 14.8 kW power output Inverter. That does not cover ambient temperatures above 38 deg C.

However, most Inverters have  air cooling and some have auto degrading, so instead of reducing the maximum power output by nearly 33 %, it could drop by around 13% at 38 deg C. If for whatever reason the cooling fan stops working, the degrading can go down to 33% at 38 deg C ambient.

This information is important to understand one of the risks of a Solar Power Generator better and what to budget for, you definitely don’t want to install it in direct sunlight. Temperature is a reality and in cheaper Inverters, the fans do fail. How hard the fan will have to work to protect your Inverter, does have a say in how long the Fan can last. Imagine relying on a small fan to protect and keep your system from failing.

💡 So what does this mean for system design?

If you size your inverter purely on panel wattage and sunlight hours, you risk thermal throttling—where the inverter intentionally reduces output to protect its internal switches and semiconductors.

✅ In my designs, I also factor in:

Johannesburg’s summer highs and roof heat PV output reduction

Manufacturer temperature derating curves.

Client load expectations during peak heat hours.

Client power management strategy for  peak summer times. Bearing in mind the summer is long and hot.

This ensures your system delivers reliable power, not just theoretical capacity.

📈 Educated clients make better decisions. That’s why I build guides and decision matrices that explain these nuances—so my clients don’t just buy a system, they understand it and are aware of the risks.

If you're considering a new Solar system or upgrading a solar system in a hot climate, temperature-aware sizing isn’t optional—it’s essential.

Let’s build smarter. Let’s build resilient. Next we will take a look at specific Inverters brands and temperature.

#SolarDesign #Sigenergy #HybridInverter #TemperatureDerating #JohannesburgSolar #ClientEducation #EnergyResilience #SmartSizing #SolarEngineering

Always On Energy client Solar education.