Why Solar Panels Dip in Delhi’s Fog but Work So Well in Ladakh’s ‘Cold’ Sun?

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?”

Advertisment

Add The Better India As A Trusted Source

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.

Solar panels run on light, not heat

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 blazing May afternoon in Jaipur or Nagpur can be harder on panels than a crisp, sunny winter day in Shimla.

Cold air can help — if sunlight is available

Because of this negative temperature effect, solar panels often perform very efficiently in cold but sunny conditions. This is well documented in alpine and high-latitude regions across the world, where PV systems operate reliably in sub-zero temperatures for decades.

Ladakh is a powerful Indian example. Despite its harsh winters, the region receives exceptionally strong sunlight because of its high altitude, thin atmosphere, and large number of clear days. Studies consistently show that parts of Ladakh receive around 6 to 6.5 kilowatt-hours of solar energy per square metre per day—among the highest in the country.

In theory, a rooftop panel in Leh on a clear winter afternoon can operate at excellent efficiency. The cold air keeps the panel cool, while strong sunlight drives electricity generation.

So if cold is not the enemy, why does winter generation dip so sharply in much of North India?

The real culprit: fog, smog, and a low winter sun

For cities across the Indo-Gangetic plains, winter is not just colder—it is murkier.

Fog, smog, and particulate pollution scatter and absorb sunlight before it ever reaches your rooftop. Even when the sun is visible, the intensity of light can be drastically reduced.

Recent analyses of winter solar performance in northern India show that prolonged smog episodes can reduce solar irradiance by 30–50% during peak winter months in bad years. In January, some regions experience hazy conditions for more than half the month.

This means less light reaches the panels, and less electricity is produced—regardless of how efficient the panels themselves might be.

For a homeowner in Delhi, this often looks like:

• Healthy generation on clear March days
  

• Sharp dips during long smoggy stretches in December and January
  

Importantly, this is not a hardware failure. It is an atmospheric one. If you removed pollution but kept the cold, winter solar performance would likely improve.

What about snow in hill towns?

In the mountains, the concern shifts from smog to snow.

In places like Shimla, Auli, or parts of Uttarakhand and Himachal Pradesh, snowfall can temporarily cover panels. When this happens, electricity generation can drop sharply—sometimes close to zero—until the snow clears.

Research from snowy regions worldwide shows three consistent patterns:

• Thin snow layers still allow some light through, reducing but not stopping generation
  

• Heavy, wet snow can block panels almost entirely
  

• Annual losses from snow are usually modest—often between 1% and 12% over a full year
  

Why aren’t losses higher? Because solar panels are typically mounted at an angle and are dark in colour. Once sunlight hits them, even weak winter sun can warm the surface slightly, helping snow slide off under gravity.

Design matters here. Steeper panel tilts shed snow more easily. Frames or ledges at the bottom of panels can trap snow, delaying recovery until manual clearing.

India’s Himalayan paradox: cold but solar-rich

India’s Himalayan states present an interesting paradox. Despite harsh winters, they possess strong solar potential.

Uttarakhand, for instance, receives roughly 280 to 287 sunny days a year. Studies estimate solar energy availability between 4 and 7 kilowatt-hours per square metre per day. Ladakh receives even more sunlight annually.

This is why solar is increasingly seen as a complement—or even an alternative—to hydropower in these regions, especially as climate change affects river flows and snowfall patterns.

Three Indias, three winter solar realities

Seen together, India’s winter solar story falls into three broad zones:

1. Polluted plains and big cities

(Delhi, NCR, Lucknow, Patna)

Here, winter losses are driven mainly by fog and air pollution. Even efficient panels cannot compensate for reduced sunlight. Monthly generation can fall dramatically during prolonged smog episodes.

2. Cool but clear regions

(Rajasthan, Gujarat, parts of Madhya Pradesh)

These areas enjoy clearer winter skies. While days are shorter, sunlight remains strong. Generation dips slightly, but lower temperatures can actually improve efficiency on sunny days.

3. Himalayan and high-altitude regions

(Ladakh, Uttarakhand, Himachal Pradesh)

These regions combine cold air with strong sunlight. Snow causes short-term disruptions, but annual solar potential remains high when systems are properly designed.

Does winter ruin your solar payback?

Most rooftop solar systems in India are designed based on annual energy generation, not monthly highs or lows.

Seasonal swings are expected. Strong summer and post-monsoon output usually compensates for winter dips.

What matters is whether your yearly generation broadly matches the assumptions used when you installed the system. Recent modelling increasingly accounts for air-pollution-related losses, suggesting that some regions may see 3–10% lower long-term generation than older estimates.

This may slightly stretch payback periods, but it does not fundamentally break the economics—especially when combined with net-metering benefits and subsidies under schemes like PM Surya Ghar.

Designing for winter: what homeowners should know

If you already have solar—or are planning it—winter performance improves with a few smart choices:

Get tilt and orientation right

South-facing panels with a tilt close to your latitude work well in most of India. In the hills, a slightly steeper tilt can improve winter performance and help snow slide off.

Plan for snow and wind

In mountain regions, mounting structures must be rated for high snow and wind loads. Avoid panel frames that create ledges where snow can accumulate.

Be realistic about pollution

In cities like Delhi, no amount of cleaning can fix week-long smog. But keeping panels free of dust and soot ensures optimal performance on clearer days.

Monitor data, not myths

Tracking generation over months helps distinguish normal seasonal dips from real faults. Many perceived “failures” are simply winter variability.

So, should winter stop you from going solar?

Winter will change what you see on your solar app—especially in North India. Foggy days mean fewer units. Snowy days may mean temporary zeroes.

But the science is clear:

• Cold improves panel efficiency
  

• Snow losses are manageable with good design
  

• Pollution, while serious, does not erase India’s vast annual solar potential
  

From Ladakh’s high-altitude plateaus to Delhi’s crowded rooftops, solar power continues to deliver meaningful energy savings across seasons. Winter doesn’t kill solar—it simply demands smarter design, realistic expectations, and attention to local conditions.

Sources

‘High-Resolution Solar Energy Parameters Under the Climate Change Scenario for Jammu and Kashmir and Ladakh Region': by S Verma and C Singh for ISPRS Archives, published on 1 June 2022.

'Snow as a Factor in Photovoltaic Performance and Reliability': by Burnham and Laurie B for Sandia National Laboratories, Published on 29 February 2020.

'Solar power generation in India hit by winter air pollution: Solargis': by Uma Gupta for PV Magazine, Published on 22 April 2024.

'Solar power could emerge as a dependable energy alternative for Uttarakhand': by Muskaan Kapoor for Mongabay, Published on 18 November 2021.

'Temperature Coefficient of PV Modules Explained': by RenewSys India, Published on 13 October 2023.

'Solar Resource Assessment & Technology Roadmap Report: SEI-1': by CSTEP, Published in August 2014.

'Can Ladakh’s Harsh Climate Help It Emerge as India’s Solar Energy Leader?': by The Better India, Published on 30 June 2025.