How Much This Is in Numbers

The general guideline is that winter generation amounts to approximately twenty to forty percent of summer generation, depending on the region, installation angle, and weather. This is more clearly seen in a specific example. A panel with a peak power of one hundred watts produces approximately seventy-three to seventy-five watts on a clear winter day, around forty-eight watts in variable cloudiness, from seventeen to twenty-eight watts on an overcast day, and only around ten watts on an overcast day with snow cover on the panel. That is, the result over a day can differ several times depending on the weather, and it is worth planning based on the lower limit rather than the average. The picture also differs by region. For Kyiv region, approximately one hundred fifty to two hundred kilowatt-hours per square meter per winter season are cited, for the south of the country up to two hundred fifty to three hundred, and for the Carpathian region around one hundred to one hundred fifty due to greater cloudiness.

Cold Does Not Harm Panels

Low temperature itself does not reduce efficiency, but rather the opposite, since semiconductor elements work better in cool conditions than in heat. The problem with winter lies not in frost, but in the short daylight hours, the low position of the sun above the horizon, and cloudiness. That is, a clear frosty day provides better conditions for a panel than a hot July midday, it simply lasts much less.

Snow Is the Main Obstacle

Even a thin layer of snow works like a dense curtain and blocks generation almost completely. There is also good news here, since the surface of the panels is smooth, and the panels themselves warm up slightly during operation, so snow often slides off them on its own under its own weight. The key factor for self-cleaning is the angle of inclination, and at an angle of approximately thirty to forty-five degrees, snow slides off much more readily. If the panels are installed at a summer house where you visit occasionally, this should be taken into account at the installation stage, since there will be no one to clean them after every snowfall.

About the Angle of Inclination

The optimal angle for Ukraine in general is considered to be approximately forty to forty-five degrees.

For winter, a steeper angle is more advantageous, meaning approximately forty to sixty degrees, since it catches the low sun better and at the same time helps snow slide off. Adjustable structures make it possible to change the angle according to the season, and for ground-mounted systems this is a real advantage. Automatic sun-tracking systems exist, but they are considered worthwhile only when they cost no more than approximately forty percent of the cost of the panels themselves with installation.

Cloudiness Does Not Stop Generation

Photovoltaic cells also work with diffused light, so generation decreases on an overcast day, but does not disappear. The decrease depends on the density of the clouds and can range from five to ninety percent. The practical conclusion is that winter generation is not so much low as unpredictable, and this is precisely what distinguishes it from summer generation.

What You Can Really Expect in Winter

Now the most important thing, since this is exactly where disappointment arises. A solar panel in winter will not provide a house with electricity, will not power a heater, and will not replace the grid. But it can maintain the charge of batteries and power basic electronics, meaning lighting, a router, and security systems. That is, the correct scenario is that the panel works not as a power source, but as a charger for an energy storage device, which you then use during an outage. This is a fundamental difference in expectations, and it is precisely what determines whether you will be satisfied with the purchase.

I wrote about selecting the storage device itself in separate materials.

About Station Kits

Kits consisting of a portable power station and a solar panel are actively sold as a solution for the blackout period. They should be evaluated realistically. In winter, the panel will produce a fraction of its rated power, so the time required to fully charge the station will stretch several times compared with summer, and on overcast days with snow, charging may barely progress. The practical approach is to consider the panel as an addition to charging from the grid, rather than as a replacement for it. That is, the main source of replenishment in winter is a socket during periods when electricity is available, while the panel adds energy on sunny days. For a summer house or a home without a stable connection, the situation is different, since there is no alternative there, and even slow charging is better than no charging at all.

Balcony and Facade

One interesting point for apartments.

With vertical mounting on a facade or balcony, panels in winter can work more efficiently than on a roof, since the low sun falls on them at a more favorable angle, while snow does not remain on a vertical surface. An additional factor is light reflected from the snow, which increases the overall output. In summer, the situation is reversed, since the high sun is unfavorable for a vertical surface. That is, for an apartment, this is a solution with pronounced seasonality, and it should be evaluated specifically based on winter performance.

What Increases Winter Generation

The correct angle of inclination, preferably with the possibility of seasonal adjustment. Cleaning from snow, dirt, and leaves, and for hard-to-reach locations, a sufficient angle for self-cleaning. The absence of shading, since the sun is low in winter, and the shadow from trees, poles, or a neighboring building falls significantly farther than in summer. Increasing the number of panels, since additional modules compensate for the lower output of each one. Monitoring through the inverter application, which allows you to see the actual figures instead of assumptions.


Sources

UNIAN publications with comments from energy experts, Atmosfera, Green System, Solar Tech, Svoja Energia blogs