On a foggy January morning in Delhi, many rooftop solar owners open their monitoring apps and feel a familiar anxiety. The units generated overnight look disappointingly low. Messages start flying on housing society WhatsApp groups: “Are the panels not working?”, “Does solar fail in winter?”

Similar doubts surface in Shimla after a snowfall, or in Leh, where the sun feels piercingly bright but the air is bitterly cold. How can solar power work when it’s freezing? And why does it struggle in cities that are technically warmer?

The answer lies in a mix of physics, geography, and something far closer to home: air quality.

The truth is simpler—and more reassuring—than many people realise. Solar panels do not stop working in winter. In fact, cold weather can improve their efficiency. What really affects winter performance in India is how much sunlight reaches the panels, and what stands between the sun and your roof.

A common misconception is that solar panels need warmth to function. They do not.

Solar photovoltaic (PV) panels generate electricity when sunlight—made up of tiny particles called photons—hits a semiconductor material, usually silicon. These photons knock electrons loose, creating an electric current. As long as light reaches the panel, electricity can be produced.

Panels are tested under standard laboratory conditions: a cell temperature of 25°C and sunlight intensity of 1,000 watts per square metre. Real rooftops, however, rarely match these conditions.

Two factors mainly determine how much power a panel generates:

How much sunlight reaches it (known as solar irradiance)

How hot the panel itself becomes

Here’s the counterintuitive part: solar panels actually lose efficiency as they get hotter. Most crystalline silicon panels used in India lose about 0.3% to 0.5% of their output for every degree Celsius above 25°C. In simple terms, extreme heat makes panels less efficient at converting sunlight into electricity.

That’s why a........

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