Do Solar Panels Work in Winter and Cloudy Weather?
Yes, solar panels work in winter and on cloudy days. They generate electricity from daylight, not heat, so cold weather does not stop them working. However, shorter days and weaker sunlight mean a solar PV system normally produces less electricity in winter than in summer. [1]
The important question is not whether solar panels work through winter, but what you can realistically expect from your roof. A good proposal should explain the quieter months as clearly as the sunnier ones.
Do solar panels need direct sunlight?
No. Solar panels can use both direct sunlight and light scattered by the atmosphere, known as diffuse light. That is why they can generate electricity when the sun is hidden behind clouds. [2]
However, “cloudy” covers everything from a bright, hazy morning to a dark afternoon under thick cloud. Your output will not be the same in both conditions. There is no single cloudy-day percentage that reliably describes every roof and every sky. [2]
Cloud cover reduces the available solar energy; it does not automatically make a roof unsuitable for solar.
Why do solar panels produce less electricity in winter?
Winter gives a solar system less daylight to work with. Days are shorter, sunlight is less intense and cloud can reduce it further. The lower sun also makes it important to assess shading from nearby buildings, trees and other obstructions. [1] [5]
Cold temperatures are not the main problem. With the same amount of light reaching them, typical silicon solar panels can operate more efficiently when cooler. But this does not cancel out the shorter days or mean that winter usually produces more electricity than summer. [3]
A bright, cold day can therefore be a useful generating day. A long spell of dark weather will tell a different story.
How much electricity do solar panels generate in winter?
There is no honest one-size-fits-all figure. Output depends on your location, system size, roof direction and pitch, shading, and the weather. For a useful forecast, ask for estimated monthly generation for your property, not just an annual total divided by 12. The European Commission’s PVGIS tool is one source of location-based monthly and annual estimates using historical weather data. These are estimates, not guarantees. [4]
It also helps to understand the difference between a system’s size and the energy it produces. A 4 kWp system describes its rated peak power under standard test conditions. It does not mean it will supply 4 kW throughout every daylight hour. Actual generation is recorded in kilowatt-hours, or kWh. [5]
For example, an average output of 1 kW over two hours produces 2 kWh. That is why the day’s total is usually more useful than a single screenshot of your system’s highest power reading.
Does solar need to power the whole house to be useful?
No. Consider this simple example, which is an illustration rather than a generation forecast:
Your solar system is supplying 800 watts, while your home is using 1,200 watts. With no battery contribution, solar supplies 800 watts and the grid supplies the remaining 400 watts.
You are still buying less electricity from the grid, even though solar is not covering everything. This is a more realistic way to think about winter solar than expecting complete independence from your electricity supplier.
Are solar panels worthwhile in South Wales?
They can be, but the assessment needs to suit the property. Roof orientation, shading, installation cost, electricity use and tariffs all affect the outcome. A clear roof with well-matched daytime demand is a different proposition from a heavily shaded roof on a home that uses most of its electricity after dark. [5]
At GMI Electrical, our work includes solar PV installations at schools across South Wales. The right questions for a school, business or home are not necessarily the same.
Our recommendation is to ask how the proposed system fits your building and when you use electricity. Do not judge it only by a sunny-day demonstration, and do not dismiss it because of one grey week.
Does battery storage help in winter?
Battery storage can make a solar system more useful, but a battery stores energy; it does not create it.
When your panels produce more electricity than your home needs, a compatible battery can store the surplus for later. In winter there may be less surplus, so it is important not to assume that solar alone will fully recharge the battery every day. [6]
Some systems can also charge from the grid during cheaper tariff periods. The value depends on your actual tariff, usage and equipment, including energy lost during charging and discharging. This needs checking rather than assuming that every battery will pay for itself. [6]
We can discuss both options as part of our solar PV and battery storage service.
What happens in rain, frost and snow?
Rain: Cloud can reduce generation, but rainfall also helps wash away some surface dirt. It is not a substitute for checking panels where leaves, bird droppings or other deposits are building up. [7]
Frost and snow: Cold air alone is different from ice or snow physically covering the panel. Coverage can reduce the light reaching the cells and substantially reduce output. Heavy accumulation can also create loading concerns. [3]
Do not climb onto a roof or scrape panels to recover a little generation. If snow accumulation or damage concerns you, contact your installer for advice. [3]
How to get more from your solar panels during winter
Use available generation when it suits your household
Where practical, move flexible electricity use into generating hours. For example, a washing cycle may fit better into a bright part of the day than the evening. Check your actual import and export tariffs before assuming that using every unit yourself is always the cheapest option. [5]
Do not leave washing machines, tumble dryers or dishwashers running while you are out or asleep simply to chase an energy saving. Follow the manufacturer’s instructions. [8]
Keep an eye on performance and visible obstructions
Review your monitoring data regularly and look for visible dirt, leaves or damage from a safe position. Your installer can advise whether cleaning or another check is needed. Avoid making a judgement from one poor day alone. [7]
Check that your app is actually updating
A blank or flat graph does not always mean the panels have stopped producing. A communication problem can prevent generation data reaching the monitoring app even while the system is operating. Check the last-update time and follow your manufacturer’s guidance. [9]
Low winter output or a fault: when should you call an installer?
Lower generation in winter is expected. Persistent missing data, an error message or an unexplained change deserves a closer look. SolarEdge, for example, distinguishes between a system producing power and one in standby, and recommends contacting the installer when further help is needed. [1] [10]
Have your system details, screenshots, error messages and the approximate date the problem started ready. That gives your installer something useful to investigate. Do not open electrical enclosures or repeatedly reset equipment to try to force it to generate.
Frequently asked questions
Do solar panels work at night?
Domestic solar PV systems do not produce useful solar electricity at night. A battery may supply energy stored earlier; otherwise, a grid-connected home draws electricity from the grid. [6] [10]
Why is my solar battery not fully charging in winter?
There may not be enough surplus solar after your home’s daytime use. Your installer can check whether this matches expected generation and whether the battery settings and any grid-charging schedule are appropriate. [6]
Will solar panels work during a winter power cut?
Not automatically. Standard grid-connected solar usually shuts down during a power cut. A battery does not guarantee backup either: the system needs suitable equipment and configuration to supply your home safely when the grid is unavailable. [1]
Thinking about solar panels in South Wales?
GMI Electrical designs and installs solar PV and battery storage systems for homes and businesses across South Wales, with our head office in Nelson.
Tell us your postcode, approximate annual electricity use and whether you are considering solar panels, battery storage or both. We can discuss the options for your property and what to consider across the whole year, including winter.
Contact GMI Electrical to discuss your solar installation, call 01443 526016 or email info@gmielectrical.co.uk.
Comments