Do solar panels produce more energy when it’s hotter?

Do solar panels generate more electricity as temperatures increase?

Since solar panels rely on the sun’s energy, it’s common to think that they will produce more electricity when temperatures rise. However, that’s not the case.

Photovoltaic solar systems convert direct sunlight into electricity. Therefore, these panels don’t need heat; they need photons (light particles).

‘The optimal operating temperature for a solar panel is below 25 °C.’

When temperatures rise, so does the temperature of the cells, which can reduce their electrical output.

According to UNEF, the optimal operating temperature for a solar panel is below 25°C. Higher temperatures can negatively impact efficiency.

This thermal response doesn’t prevent daily production from being high in summer. Despite the heat, there are more hours of solar radiation, with little cloud interference.

The difference between photovoltaic solar energy and solar thermal energy

While photovoltaic solar energy converts light into electricity, solar thermal energy actually uses the sun’s heat as its main source.

The system heats a fluid —usually water or thermal oil— which is stored or distributed for uses such as heating, domestic hot water, or industrial applications.

This technology is especially efficient in warm, sunny regions. The hotter it is, the better it works, since its performance is directly linked to its ability to capture and retain that heat.

Although both technologies rely on the same natural resource —the sun— they work based on different principles: one thermal, the other photovoltaic.

How does temperature affect solar panels?

In photovoltaic systems, performance primarily depends on light, but temperature also plays a role. When solar cells heat up, their electrical behaviour changes: voltage decreases and conversion efficiency drops. This effect is factored into the panel’s design.

The key lies in the balance between light capture and thermal management. In hot climates, installations are designed with proper ventilation to help dissipate heat. Even so, production is affected.

Additionally, depending on the solar module’s design, the loss of efficiency due to higher temperatures can vary. For example, differences between types of modules can amount to up to 5% additional efficiency loss during the summer months.

‘In summer, total daily production increases since there are longer sunlight hours.’

So, even if immediate efficiency is lower in summer, overall daily energy production can be higher thanks to longer days, better sun angles, and steady direct radiation. 

And in winter? Do solar panels work better when it’s cold?

A cold, clear, windy day can deliver very high performance. Direct sunlight activates electricity production, while low temperatures allow the cells to work in a stable environment.

Wind also acts as a natural cooling system and helps keep the panels’ surface clean. This allows the system to operate closer to peak efficiency for longer hours.

Still, with fewer daylight hours, cumulative production is lower than in summer. But this isn’t due to temperature —it’s due to lower solar availability.

This balance between efficiency and daily production is why overall system performance is measured using a technical indicator: the performance ratio (PR).

Concept and relevance of the performance ratio (PR)

The performance ratio (PR) measures the actual performance of a solar installation compared to its theoretical maximum, as explained by NREL (National Renewable Energy Laboratory).

It’s a technical index that factors in temperature, wiring losses, and dirt accumulation.

It helps interpret seasonal variations. For instance, in summer, PR can drop due to heat buildup, even if total production is high. In winter, PR may rise thanks to thermal stability, despite shorter days.

A PR between 0.75 and 0.9 is considered normal for modern installations. This figure allows industry professionals to confirm whether a solar plant is performing properly, avoiding misinterpretation of production data simply based on whether it’s hot or cold.

Factors that influence solar panel performance

A solar panel’s efficiency is determined by a wide range of technical and environmental factors beyond temperature:

• Type of solar cell: Monocrystalline cells offer higher efficiency and take up less space. Polycrystalline and thin-film cells perform worse and are more sensitive to heat but are more affordable and versatile.
• Available solar radiation: The more direct sunlight hits the panel, the more electricity is generated.
• Panel orientation and tilt: Adjusting the angle according to latitude and season is key to maximising solar capture.
• Cleanliness: Dust or dirt on the panel surface blocks light and reduces performance.
• Design and materials: Component quality, cell arrangement, and the colour of the protective layer also affect output.
• Ageing of the module: Over time, solar modules gradually lose efficiency due to component wear.

Ultimately, solar panel production increases with the amount of sunlight hitting the modules throughout the day. In summer, sunlight is more abundant. The difference between solar thermal and photovoltaic solar energy lies in the fact that thermal technology harnesses heat, while photovoltaic depends on light —where heat has a negative effect on performance.