How Much Electricity Do Solar Panels Generate in Penzance?

The headline figure

A south-facing solar array on a 35-degree roof in Penzance produces about 1,099 kWh a year for every kilowatt-peak (kWp) installed, according to PVGIS, the European Commission's photovoltaic model. A typical 4 kWp home system — about ten modern panels — therefore generates roughly 4,400 kWh in an average year.

All figures in this article come from PVGIS 5.3 using SARAH-3 satellite radiation data for 2005–2023, crystalline silicon panels, fixed mounting and the model's standard 14% allowance for system losses such as cabling, inverter efficiency and dirt. They are long-term averages for Penzance itself (50.12°N, 5.54°W); an individual year can come in above or below.

Output by roof direction

Roof direction (35° pitch)	kWh per kWp per year	4 kWp system
South	1,099	≈4,400 kWh
South-west	1,046	≈4,180 kWh
South-east	1,026	≈4,100 kWh
West	887	≈3,550 kWh
East	861	≈3,440 kWh

South-west and south-east roofs lose only about 5–7% against due south. East and west roofs lose about a fifth, but they spread generation into the morning or evening — a west roof in Penzance still produces useful power when many households start cooking and running appliances. Many terraces have one east-facing and one west-facing slope; panels on both can make sense where the roof area allows.

Does roof pitch matter?

South-facing pitch	kWh per kWp per year
10° (low-pitch or flat-roof frame)	1,005
20°	1,060
35°	1,099
45°	1,094

Pitch matters much less than direction. Anything between about 30° and 45° is close to the best Penzance can do, and even a shallow 20° roof gives up less than 4%. A 10° frame on a flat roof loses about 9% but keeps panels low, which helps on exposed seafront roofs. Remember that a flat-roof array in a conservation area needs a prior approval application before installation.

Month by month

Month	kWh per kWp (south, 35°)	4 kWp system
January	40	160
February	58	232
March	92	368
April	127	508
May	136	544
June	135	540
July	134	536
August	125	500
September	102	408
October	71	284
November	45	180
December	33	132

April to September produces about 69% of the year's output. May's generation is roughly four times December's.

What the seasonal shape means for export and batteries

Because so much of the output arrives in the middle of summer days, a solar-only home in Penzance typically exports a good share of what it generates. Export is paid under the Smart Export Guarantee: Outgoing Octopus Fixed paid 12p per kWh when we checked in August 2026, so every 1,000 kWh exported earns £120 at that rate. You need an MCS-certified installation and a smart export meter, and you can sell export to a different supplier from the one you buy from.

A battery changes the split by storing daytime surplus for the evening. Whether it pays back depends on how much you use in the evening, your import tariff and the battery's cost, so the right answer comes from your own consumption data rather than a rule of thumb. In December, when a 4 kWp array averages about 4 kWh a day, there is little surplus to store; in May there can be plenty.

Why your roof may differ

• Shading from chimneys, neighbouring buildings and rising ground can cut output well below these averages, especially in winter when the sun is low.
• Salt on seafront roofs can build up on the glass between rain showers; rain usually clears it, and panels certified to IEC 61701 are tested for salt-mist corrosion.
• Inverter size: a single-phase inverter above 16 A (3.68 kW) per phase needs a G99 application or an export limit, and an array much larger than its inverter will clip output on the brightest days.

Getting figures for your own home

At a survey we measure your roof's actual pitch, orientation and shading and model the array from those, rather than from a town average. For installation details — planning in the Penzance conservation area, listed buildings on Chapel Street, and salt-air specification for Newlyn and Mousehole — see our page on solar panels Penzance. For prices, see solar panel costs in Cornwall.