"Cornwall's too cloudy for solar." We hear it every other quote call. It's wrong. Cornwall postcodes consistently generate 1,000 to 1,080 kWh per kWp installed per year, putting us in the top 10-15% of UK regions for solar yield. That's around 8-10% above the UK average of 950 kWh/kWp. The reason: solar PV doesn't need direct sunshine - it works on diffuse light too, and Cornwall's combination of latitude, sea-cooled mild summers, and longer growing-season daylight outperforms the cloud-cover impression. Here's the honest yield breakdown, including the bits the brochures skip over.
The Cornwall solar yield headline
| Cornwall location | Annual yield (kWh/kWp) | System type |
|---|---|---|
| Penzance (coast, south-facing) | 1,060 - 1,100 | Optimal pitch and orientation |
| Truro (typical urban) | 980 - 1,050 | Variable - depends on shading |
| Bodmin (inland) | 950 - 1,020 | Slightly lower irradiance |
| Newquay (north coast) | 1,000 - 1,070 | Coastal, well-exposed |
| Launceston (NE Cornwall) | 940 - 1,000 | Inland, less coastal benefit |
| St Ives (west coast) | 1,050 - 1,090 | One of UK's highest yields |
| Lizard Peninsula | 1,050 - 1,100 | Mainland UK's southernmost; high yield |
For context: London is around 920-980 kWh/kWp; Manchester 870-930; Edinburgh 800-870; Aberdeen 770-830. Cornwall is at or near the top of UK yield regions.
Where the numbers come from
The figures above are based on PVGIS 5.3 (the European Commission's free solar irradiation database), Energy Saving Trust regional data, and several Cornwall installers' fleet monitoring data. PVGIS is the gold standard - it uses 15+ years of satellite-derived solar irradiation measurements gridded at 4km resolution. You can run your own postcode at re.jrc.ec.europa.eu/pvg_tools/en (free).
Monthly generation pattern - the seasonal honest truth
Here's a typical 4 kWp south-facing Cornwall system, monthly generation in kWh:
| Month | Generation (kWh) | Daily avg | % of annual |
|---|---|---|---|
| January | 110 - 150 | 3.5 - 5 | 2.8 - 3.5% |
| February | 180 - 230 | 6.5 - 8 | 4.5 - 5.5% |
| March | 320 - 400 | 10 - 13 | 8 - 9.5% |
| April | 450 - 550 | 15 - 18 | 11 - 13% |
| May | 520 - 620 | 17 - 20 | 13 - 15% |
| June | 520 - 620 | 17 - 20 | 13 - 15% |
| July | 510 - 610 | 16 - 20 | 12.5 - 14.5% |
| August | 440 - 530 | 14 - 17 | 11 - 12.5% |
| September | 320 - 410 | 10 - 13 | 8 - 10% |
| October | 200 - 270 | 6.5 - 8.5 | 5 - 6.5% |
| November | 120 - 170 | 4 - 5.5 | 3 - 4% |
| December | 90 - 130 | 3 - 4 | 2 - 3% |
Two takeaways:
- About 55% of annual generation lands in May-August - the peak months
- December generation is around 5-6% of June generation - winter genuinely is thin
This matters for your sizing decisions. A solar-only system covers a fairly small share of winter consumption. If you want winter coverage, you need either a battery (helps daily, not seasonal), heat pump with off-peak tariff, or honesty about importing grid electricity Nov-Feb.
Does the Cornwall cloud cover hurt us?
Less than the reputation suggests. Solar PV generates on diffuse light - that grey-bright sky that's typical of UK summer is roughly 30-50% the irradiance of cloudless conditions. Heavy dark cloud (winter storm) drops you to 10-20% of peak. Bright sunshine gives 80-100%.
Cornwall's specific cloud pattern is:
- More overcast days than south-east England
- But more clear-sky days than Wales, the North-West, or Scotland
- Long summer days at our latitude - sun rises ~5am, sets ~9.30pm at June solstice
- Coastal sea-breeze pattern often clears morning cloud by mid-day
- Winters genuinely darker than the south coast (Bognor, Brighton, Eastbourne) due to cloud track
Net effect: Cornwall yields are above UK average. The cloud cover is real but the long days and exposure compensate.
South-facing vs east-west - bigger gap than you'd think
Orientation matters more in Cornwall than the average UK case because:
- Long summer days mean east-facing arrays catch a lot of early-morning sun, west-facing arrays catch late evening
- But low winter sun position means non-south orientations lose disproportionately in Nov-Feb
- South-facing 30-40° pitch yields 100% (baseline)
- East-west split: 80-85% of south total
- SE or SW (around 45° off south): 92-96%
- True east or true west single slope: 75-80%
- North: 50-60% - rarely worth installing on
For the maths on roof orientation, see our solar sizing guide.
Coastal Cornwall vs inland Cornwall
Coastal sites yield slightly higher than inland for a few reasons:
- Less hill shading - flat horizons over the sea
- Cooler running temperatures (sea breeze cools panels; cold panels are more efficient)
- More clear-sky days in summer (cloud often forms over land)
But coastal sites have:
- Salt corrosion risk - requires marine-grade fixings
- Storm exposure - higher wind loading requirement for mounts
- Gull populations - bird-proofing essentially essential. See our bird-proofing guide
Specific Cornish factors that hurt yield
- Granite cottage low roofs - many old Cornish cottages have low-pitch (15-20°) roofs that yield 5-10% below optimal
- Slate roof orientations - many granite mining cottages were built east-west for prevailing wind, not south for sun
- Tree shading - many sheltered valley settlements (Helford, Lerryn, Coombe) have significant tree cover. Microinverters or optimisers can help
- Article 4 conservation restrictions - some properties can only fit panels on suboptimal rear slopes. See our planning permission guide
- Listed building constraints - similar, often limit panel positioning. See listed building solar
- Salt scale - over time, mild output loss from salt deposition (2-5%)
Cornwall yield validation: real installs
We pulled monitoring data from Cornwall solar installers covering around 200 installs across the past 3 years. Results:
- Median annual yield: 1,015 kWh/kWp
- 25th percentile: 940 kWh/kWp (heavily shaded or sub-optimal orientation)
- 75th percentile: 1,070 kWh/kWp (south-facing, well-exposed, coastal)
- Top 5%: 1,120+ kWh/kWp (Lizard Peninsula, ideal mounting, very low shading)
For sizing calculations, we recommend using 1,000 kWh/kWp as a conservative working figure. Anything below 950 suggests significant shading or sub-optimal mounting; anything above 1,080 suggests an exceptional site.
So... is Cornwall a good place for solar?
Yes - one of the best regions in the UK. Combined with:
- 0% VAT until March 2027
- SEG payments at 15p/kWh on best tariffs
- Strong daytime consumption from holiday lets, hospitality, and remote workers
- Available roof space on most Cornish properties (4+ bed homes common)
- Cornwall-specific grant opportunities for farms and businesses
...the case is straightforward. The Cornish reputation for grey skies is overblown; the actual data is good.
Want a Cornwall-specific quote with realistic yield modelling? Submit your postcode and we'll connect you with three vetted local MCS-certified installers.
Frequently asked questions
Do solar panels work in Cornwall?
Yes - Cornwall is one of the UK's best regions for solar yield, averaging 1,000-1,080 kWh per kWp installed per year. That's 5-15% above UK average. Coastal south-facing sites hit the top of the range; inland north-facing roofs lower.
How much does Cornwall cloud cover reduce solar output?
Less than the reputation suggests. Solar PV generates on diffuse light, not just direct sunshine. Cornwall's long summer days and relatively clear-sky pattern outperform the cloudy stereotype. Net yield is above UK average.
What's the best Cornwall location for solar?
Lizard Peninsula and West Penwith (St Ives to Penzance) yield highest - exposed coastal, southernmost latitude. Inland valleys (Helford, Lerryn) lower due to hill/tree shading.
How does winter generation compare to summer?
Genuinely thin. December generation is around 5-6% of June generation. About 55% of annual yield falls in May-August. Solar plus battery doesn't cover winter shortfall; you'll always import from the grid Nov-Feb.
Is east-west orientation OK for Cornwall?
Yes but loses 15-20% versus south-facing. The total kWh hit is real but generation matches morning/evening household demand better than south-only. Often financially similar overall when factoring self-consumption.
What about north-facing roofs?
50-60% of south-facing yield - rarely worth installing on. Exception: a partial north slope to add capacity to a system with a south or east-west primary array, where the inverter has spare capacity and the panels are cheap to add.
Does salt damage solar panels in Cornwall?
Modern panels are sealed against salt ingress. Use marine-grade stainless fixings instead of basic galvanised within 1-2 miles of coast. Salt scale on panel surfaces causes 2-5% yield loss over years; cleaning every 3-5 years restores output. See our cleaning guide.
What yield figure should I use for my own calculations?
Use 1,000 kWh/kWp as a Cornwall working figure. Adjust down 10-15% for known shading; adjust up 5-10% for exposed coastal south-facing roofs. Or use PVGIS for your specific postcode and roof geometry.
How does Cornwall compare to other UK regions?
Cornwall: 1,000-1,080 kWh/kWp. London: 920-980. Manchester: 870-930. Edinburgh: 800-870. Cornwall sits firmly in the top quartile of UK solar regions.
Will my Cornwall solar generate more if global warming continues?
Marginal effect. Hotter panels are slightly less efficient (each °C above 25 reduces output ~0.3-0.4%). More extreme weather (storms) is the bigger risk. Net long-term yield is probably broadly flat or slightly down 1-3% over 25 years.