Do solar panels work in winter? Cold, snow and short days

“Panels don't work in winter” is a common myth. Solar panels make electricity from light, not heat. Cold weather does not reduce their efficiency; it improves it. What lowers output in winter is not the temperature but shorter days, a sun that sits lower in the sky and more cloudy days.

This article explains why winter output falls, by how much, and how a well-engineered project accounts for it from the start.

Cold weather is a panel's friend

The power rating on a panel's label is measured at a cell temperature of 25°C. As the cell gets hotter, power drops. That loss is expressed as the temperature coefficient: on current monocrystalline panels it is roughly 0.3 to 0.4 percent per degree.

On a sunny summer afternoon the cells on a roof can reach 60 to 65°C, a loss of around 12 to 15 percent against the label. On a clear, cold winter day the cells run close to, or even below, their rated temperature. Under the same light, a panel is more efficient in winter than in summer.

The best day for a panel is a cold, clear winter day. What is missing is not efficiency but hours of daylight.

The three things that really lower winter output

Short days. In December daylight lasts roughly two thirds as long as in June, so the panel simply has fewer hours to work.

A low sun. In winter the sun stays close to the horizon even at noon. Its light travels further through the atmosphere and strikes the panel at a flatter angle, so less energy reaches each square metre. That is why projects that need a stronger winter share use a slightly steeper tilt.

Cloud and fog. On a cloudy day a panel does not stop; it keeps producing from diffuse light, but far less than on a clear day. On an overcast winter day output can fall to between a tenth and a third of a clear day. Foggy valleys and coastal strips feel this most.

The seasonal split in numbers

Across Türkiye, roughly 60 to 65 percent of annual production happens between April and September. December and January are the weakest months, producing between a third and a half of July's output. The ratio depends on the region: the winter share is higher on the Mediterranean and in the southeast, lower on the Black Sea coast.

For scale, each kWp of panels on a south-facing roof produces about 1,600 kWh a year. A 5 kWp home system delivers about 8,000 kWh annually. Most of that falls in spring and summer; in December the same system produces a few hundred kWh.

The key point: the annual production figure in your proposal is the simulated total of all twelve months. Winter is already inside that number. Lower winter output is not a surprise; it is a known line in the investment decision.

What about snow?

A thin layer of snow lets some light through and the panel keeps producing. Heavy snow covers it completely and output stops. On pitched roofs snow usually slides off within a day or two; the dark, smooth surface of the panel speeds up melting once the sun comes out. Light reflected off surrounding snow then lifts output slightly once the panel is clear.

In heavy-snow regions two things are settled at the start of the project. First, the structural calculation: the roof and mounting are designed to carry the local snow load. Second, the layout: a gap is left below the lower edge of the panels so snow does not pile up, and the tilt is chosen to let it slide.

Do not try to clear snow from panels with a shovel or anything hard. Scratching the glass or straining the frame costs far more than a few days of lost output. If you must, a soft squeegee and safe access are enough; most of the time waiting is the right answer.

How winter output affects your bill

In winter your consumption usually rises while your production falls, so drawing more from the grid is normal. How that shows up on your bill depends on the net metering model you fall under.

For residential subscribers netting is monthly: each month is settled on its own, with what you exported that month deducted from what you imported. In summer the surplus dominates, in winter consumption does. Businesses have been on hourly netting since 1 May 2026. Our net metering guide explains which applies to you.

If you heat with a heat pump the picture shifts further: your electricity use rises in exactly the months when production is lowest. The system should then be sized on the monthly balance, not just the annual total. See our guide to choosing a heat pump for the details.

Engineering for winter

A system that shrugs off winter is one that was designed correctly from the start. These are the main points we check at the site visit:

Tilt and orientation. Facing south at a tilt of 25 to 35 degrees gives balanced output through the year. Where a stronger winter share is wanted, the tilt is made a little steeper.

Winter shading. Because the winter sun is low, a chimney, tree or neighbouring building that is harmless in summer can shade the panels in winter. We run the shading analysis on December's sun path as well.

Snow load and mounting. The local snow load goes into the structural calculation, and the mounting and fixings are chosen to match.

A realistic simulation. Annual production is calculated month by month from long-term weather data for your location. The figure in your proposal is that calculation, winter included.

In a well-sized system, winter is not a surprise. It is part of the calculation.

To see how winter and summer output would split on your own roof, our savings calculator gives a first estimate right away, and a free site visit gives you the exact figures.