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Solar · Advice

Do solar panels work in winter and on cloudy days?

Short answer

Yes, but output is much lower. Panels use daylight, not heat, so they generate on cloudy days, just less. In December a UK south roof produces around a quarter of its June output because days are short and the sun is low. Expect roughly 1 kWh per installed kWp per day in winter at best in southern England.

Last checked 24 September 2026 · 1 source

In more detail

  • PVGIS daily averages, south 35: Portsmouth Dec 1.21 vs Jun 4.63 kWh/kWp/day; Manchester Dec 0.91 vs Jun 3.69; Edinburgh Dec 0.72 vs Jun 3.70.
  • Cold, clear winter days can give high instantaneous kW (panels are more efficient when cold) but for few hours.
  • Snow cover stops output until it slides off.

The facts, dated

  1. 01
    PVGIS Portsmouth south 35: December average daily yield — 1.21 kWh/kWp/day

    market_data · England · checked 24 September 2026 · PVGIS (EU Joint Research Centre)

  2. 02
    PVGIS Edinburgh south 35: December average daily yield — 0.72 kWh/kWp/day

    market_data · Scotland · checked 24 September 2026 · PVGIS (EU Joint Research Centre)

What we saw in the field

[QA review 2026-09-24] H-10 AGREES: homeowner saw ~2 kW on cloudy summer days and ~1.5 kW on clear winter days from 5.6 kWp - plausible snapshots; daily winter energy still small. I-11 UNVERIFIABLE (consolidated): installer ground mount 737 kWh in December vs ~6 MWh in July (Dec/Jul 0.12) implies ~43 kWp and a very dull December; long-term PVGIS Dec/Jul for south 35 deg is 0.26 (Portsmouth) to 0.17 (Glasgow). See

Sources

Last checked: 24 September 2026