Commercial Solar Winter Output
Do Commercial Solar Panels Work in Winter (UK)?
Short answer: yes, every day of the year. UK panels produce 25–35% of their summer output in December–January. Cold temperatures actually improve panel efficiency. Cloud — not cold — is what reduces winter generation.
Year-round
Generation
25–35%
Dec output vs Jun
+5%
Cold-weather efficiency boost
8–10%
Typical winter share of annual yield
"Will solar work for me through a UK winter?" is one of the most common buyer questions. The answer is yes — but understanding the seasonal output curve matters when sizing the system, modelling savings, and considering battery storage. Here is the real data.
Month-by-Month UK Commercial Solar Output
For a 100kW commercial rooftop array on a south-facing UK midlands building, typical monthly generation looks like this:
- January: 3,500–4,500 kWh (~3.7% of annual)
- February: 5,500–6,500 kWh (~6.3%)
- March: 8,500–10,000 kWh (~9.7%)
- April: 11,000–13,000 kWh (~12.6%)
- May: 12,500–14,500 kWh (~14.2%)
- June: 13,000–15,000 kWh (~14.8%)
- July: 12,500–14,500 kWh (~14.2%)
- August: 11,000–13,000 kWh (~12.6%)
- September: 8,500–10,000 kWh (~9.7%)
- October: 5,500–6,500 kWh (~6.3%)
- November: 3,500–4,500 kWh (~3.7%)
- December: 2,800–3,500 kWh (~3.2%)
Annual total: ~95,000 kWh for a 100kW system in the midlands. South-coast sites generate 5–8% more; far-north Scottish sites generate 8–12% less.
Why Cold Weather Actually Helps Solar Panels
Solar panel efficiency rises as panel temperature falls. Most panels are rated at 25°C cell temperature. UK winter cell temperatures (often 5–10°C) deliver 3–5% higher peak efficiency than summer conditions. The reason December output is low is not cold — it is short daylight hours and high cloud cover.
What Drives Winter Generation Most
- Daylight hours. December UK daylight is ~7.5 hours; June is ~16.5. This alone explains ~70% of the seasonal swing.
- Solar elevation angle. Lower winter sun angle means less direct irradiance per panel. Steeper panel tilt (35–40°) optimises winter capture.
- Cloud cover. December averages 7.5 oktas (75% cloud cover) across the UK; June averages 5.5 oktas.
- Snow. Light dusting reduces output briefly; heavy accumulation can take output to zero for days. Snow slides off panels above ~15° tilt within 24–48 hours of clearing weather.
How Winter Output Affects Commercial Solar Economics
Winter is exactly when grid electricity is most expensive (peak demand, gas-set wholesale prices). A kWh of solar generated in January displaces grid electricity at typically 35–40p/kWh — versus 22–25p in summer. So while you generate fewer kWh in winter, each one is worth more.
For most UK commercial buildings, winter (Dec–Feb) accounts for ~10% of annual solar generation but ~14–16% of annual electricity bill savings.
Should I Add Battery Storage for Winter?
Battery storage shifts solar generation across hours, not across months. It does not "store summer for winter" — battery losses make seasonal storage uneconomic. Instead:
- Battery captures excess midday solar in summer for evening peak hours.
- In winter, the battery primarily provides peak-shaving and grid resilience, not seasonal balancing.
- Sites with high time-of-use tariff differentials (red/amber/green DUoS bands) often see batteries pay back faster than the panels themselves.
Winter Generation by UK Region
- South coast (Brighton, Plymouth, Bournemouth): +6–9% above midlands average; sun angle and cloud cover most favourable.
- Midlands (Birmingham, Nottingham): baseline.
- North (Manchester, Newcastle, Leeds): -3–5% vs midlands.
- Scotland central belt (Glasgow, Edinburgh): -8–12% vs midlands; longer daylight in summer compensates.
- Highlands and Islands: -12–18% vs midlands; payback economics still positive due to high commercial tariffs.
Frequently Asked Questions
Do solar panels work in winter UK?
Yes — UK commercial solar panels generate every day of the year, including in winter. December output is typically 25–35% of summer output, but every kWh generated during winter peak hours is worth more (grid prices are highest in winter).
Why is solar output lower in winter?
Three reasons: (1) shorter daylight hours (~7.5 hours in December vs 16.5 in June), (2) lower solar elevation angle reduces direct irradiance, and (3) higher cloud cover. Panel temperature has no negative effect — cold actually improves panel efficiency.
Do solar panels work in cloudy weather?
Yes. Diffuse light still drives generation — typically 10–25% of clear-sky output under heavy overcast. Modern monocrystalline panels handle low-light conditions much better than older polycrystalline panels.
Does snow stop solar panels?
Light snow dusting reduces output briefly. Heavy snow can take output to zero. Snow slides off panels installed above 15° tilt within 24–48 hours of clear weather. UK snow events affecting commercial solar are typically <10 days per year, even in northern England.
Should I size a system for winter use?
No — size for annual generation matched to annual electricity demand. The system that generates 95,000 kWh/year on a 100kW UK array is correctly sized for a building consuming 95,000+ kWh/year. Battery storage handles intra-day balancing, not seasonal balancing.
Related Guides
Ready to Reduce Your Energy Costs?
Join hundreds of UK businesses already benefiting from commercial solar. Get your free site survey and quote today.
MCS Certified | 25-Year Warranty | Nationwide Coverage