24 September 2026

Solar in a Latvian Winter: What Your Plant Really Does from October to March

Every autumn, property owners ask us the same question: does solar even work here once the days get short? The answer is yes – just not in the way many people expect. Understanding the seasonal pattern is the key to judging any solar investment correctly.

The numbers behind the seasons

At Latvia’s latitude, a well-designed system produces roughly 1,000–1,100 kWh per installed kWp per year. That output is strongly seasonal: about three-quarters is generated between April and September, while November, December and January together deliver only around 5%. A clear June day can produce more than ten times the output of an overcast December day.

Why winter does not break the business case

Banks, investors and our own financial models evaluate solar on annual yield, not monthly output. The winter dip is already built into every Sunwise forecast, payback calculation and LCOE estimate. A plant that meets its annual target is performing exactly as designed – even if its December figures look modest.

Winter even brings a few advantages:

• Cold improves efficiency. Panels lose roughly 0.3–0.4% of output for every degree above 25 °C. On a frosty, sunny March day they operate close to peak efficiency.
• Snow reflects light. Bright snow cover boosts irradiance on clear days, and bifacial modules also capture reflected light on their rear side.
• Spring arrives early. By March, production is already several times the December level – well before the heating season ends.

Snow: clear it or leave it?

On tilted panels, snow usually slides off after a few sunny days. Manual clearing can scratch the glass and void warranties, and on commercial roofs it creates safety risks. Our advice: leave it, unless the snow load approaches the roof’s structural limits – something assessed at the design stage.

A pre-winter checklist for owners

• Review monitoring data: compare autumn output with the forecast to catch faults early.
• Inspect cabling, fixings and inverter ventilation after summer storms.
• Clean off leaves and dust before the low-sun months, when every percent counts.
• Confirm snow-load calculations for flat roofs with ballasted systems.
• Review your electricity contract: winter is when you buy most from the grid, so tariff structure matters.

The bottom line

Solar in Latvia is a summer-weighted asset measured over the full year. Judged by the right yardstick, it delivers predictable, bankable returns – and a well-maintained system comes through winter ready for its most productive months.

Want a month-by-month production forecast for your property? Contact us at info@sunwise.lv.