Do Solar Panels Work on Cloudy Days?

Considering the UK’s famously unpredictable weather, it’s natural to question how effective solar panels really are when the sun isn’t shining. Cloud cover is common across the country, but that doesn’t mean solar energy stops working. 

In fact, today’s solar panels are designed to generate electricity even in low-light conditions, making them a viable option for homeowners and landlords throughout the UK.

This guide discusses how solar panels perform when it’s cloudy, the technology that helps maintain efficiency, and the real-world savings you can expect. You’ll also discover how to maximise your investment with modern solutions like battery storage.

Can Solar Panels Still Generate Electricity on Cloudy Days?

Yes, solar panels do generate electricity on cloudy days, although at reduced efficiency.

Solar panels rely on daylight, not direct sunlight, to produce electricity. According to the Energy Saving Trust, photovoltaic (PV) cells in solar panels capture light particles (photons) to generate an electrical charge, even on cloudy days. 

While their output is lower compared to sunny conditions, modern panels are designed to harness diffuse light  ensuring they remain productive year-round. This makes solar energy viable in the UK, where around 48% of the year is overcast.

For example, a typical 4kW solar PV system in the UK generates about 3,400 kWh annually. On cloudy days, it may produce 10-25% of its clear-day output, depending on cloud thickness. 

Thin or partial cloud cover allows more light through, sometimes even boosting production via the “edge-of-cloud effect,” where light intensifies briefly as clouds clear.

This ability to generate power in low-light conditions ensures solar panels remain a reliable energy source for UK homes and businesses, reducing reliance on the grid.

What Impacts Solar Panel Performance on Cloudy Days?

1. Panel Type and Technology

Modern solar panels are built to handle varied weather conditions. Monocrystalline panels, for example, perform better in low-light environments compared to polycrystalline ones due to higher efficiency rates.

Passivated Emitter Rear Cell (PERC) technology and bifacial solar panels can also harvest light more effectively from indirect sources.

According to the Energy Saving Trust, selecting high-quality, efficient panels can improve performance and energy yield even during less-than-ideal weather conditions.

2. Inverter Quality

Your system’s inverter converts solar energy from DC to usable AC electricity. High-performance inverters like microinverters allow each panel to operate independently, meaning shade or cloud cover over one panel won’t drag down the system's entire output.

3. Location and Orientation

South-facing roofs in the UK receive the most consistent solar exposure, but east- or west-facing installations still generate significant returns. Cloudy regions like Scotland or the North of England still benefit from solar, diffuse light is still usable light.

4. Seasonal Variations

Seasonal variations also play a role. The Energy Saving Trust estimates that solar output in winter can be 50-75% lower than in summer due to shorter daylight hours and increased cloud cover. 

For instance, a 4.3kW system in London produces about 8.8 kWh/day on average, but this drops to 4.9 kWh/day in December. In contrast, summer months like May or July can yield up to 25 kWh/day.

How Can You Maximise Solar Efficiency During Cloudy Weather?

To ensure your solar panels perform optimally, even in overcast conditions, several factors need consideration:

Panel Orientation and Angle

Proper orientation and tilt are critical. South-facing roofs with a pitch of 30-40° capture the most daylight, maximising output in cloudy conditions. According to the UK Government’s Solar Roadmap, east or west-facing roofs are viable but may produce 10-20% less energy. 

If shading from trees or buildings is an issue, solar optimisers can minimise losses by ensuring unshaded panels operate independently. 

Panel Quality and Efficiency

High-quality panels, such as monocrystalline PV panels, perform better in low-light conditions due to their higher efficiency rates (typically 18-22%). Cheaper polycrystalline panels may deliver 50% less power in cloudy weather.

Investing in premium panels certified by the Microgeneration Certification Scheme (MCS) ensures reliability. Check MCS-certified installers for quality assurance.

Solar Battery Integration

Solar batteries store excess energy for use during cloudy periods or at night. For a 4kW system, a 6-10 kWh battery can save an additional £1,400 per year by reducing grid purchases. 

This is especially valuable for landlords or commercial properties with high energy demands. 

If you're considering adding storage to your system, our guide on the cost of solar batteries can help you understand pricing, payback periods, and what to expect based on your energy needs.

Inverter Quality

Your system’s inverter converts solar energy from DC to usable AC electricity. High-performance inverters like microinverters allow each panel to operate independently, meaning shade or cloud cover over one panel won’t drag down the system's entire output.

Why Solar Panels Are Still Worth It in the UK’s Cloudy Climate?

Despite the UK’s cloudy reputation, solar panels remain a smart investment. Here’s why:

Save Money

Yes, they do. A 4kW system can save £190-£420 annually on electricity bills, depending on your location and usage, per the Energy Saving Trust. 

For example, households in London save around £175-£420, while those in Manchester save £165-£405. Pairing panels with the Smart Export Guarantee (SEG) allows you to earn 10-16.5p per kWh exported, further offsetting costs.

To get a clearer picture of how much solar panels can save you on your electricity bill, including what factors influence savings, check out our in-depth breakdown. 

And if you're thinking long-term, our guide to the return on investment for solar panels explains how and when your system can pay for itself.

Reduce Carbon Emissions

Solar panels cut your carbon footprint significantly. According to the Energy Saving Trust, a typical 4kW system reduces CO2 emissions by 1-1.5 tonnes annually, supporting the UK’s net-zero target by 2050. 

This is a key motivator for eco-conscious homeowners and commercial property managers.

Financial Incentives for Solar Panels

The UK Government offers schemes like ECO4, which provides free or subsidised panels for low-income households, and the Warm Homes: Local Grant, launching in April 2025. These initiatives make solar more accessible. 

The Smart Export Guarantee (SEG) also ensures you earn from excess energy, with top tariffs from suppliers like E.ON Next (16.5p/kWh).

Ready to explore solar savings? Use Eco Answers’ Quote-Comparison Tool to connect with trusted installers and get tailored quotes today.

How Can You Maximise Solar Savings as a Homeowner or Landlord?

To get the most out of your solar investment:

• •
  Use Energy During Daylight Hours: Run appliances like washing machines during the day to use free solar energy.
  
  
• •
  Install a Battery: Store excess energy to avoid peak grid tariffs, saving up to £1,400/year.
  
  
• •
  Maintain Panels: Keep panels clean and free of debris. Rain helps, but occasional cleaning boosts efficiency.
  
  
• •
  Choose MCS-Certified Installers: Ensure quality installation to maximise performance and eligibility for SEG payments.

For commercial properties, larger systems (e.g., 10kW) can power multiple units, reducing tenant energy costs and increasing property value by up to 6.8%.

If you're wondering how solar installations impact real estate, our article on whether solar panels increase property value provides insights into the latest data and what it means for landlords and investors.

FAQs

Can Solar Panels Work During Heavy Rain?

Yes, solar panels function during rain, as they rely on daylight, not direct sunlight. Rain can even clean panels, improving efficiency by removing dust. However, heavy rain reduces output to 10-20% of clear-day levels.

Do Solar Panels Work at Night?

No, solar panels don’t generate electricity at night, as they need daylight. A solar battery can store daytime energy for nighttime use, reducing grid reliance.

How Does Snow Affect Solar Panel Performance?

Snow can temporarily block light, reducing output. However, panels’ smooth surfaces and tilt often cause snow to slide off. Regular maintenance ensures minimal disruption.

Are There Specific Panels Better Suited for Cloudy Climates?

Monocrystalline panels are best for cloudy climates due to their high efficiency (18-22%) in low-light conditions. Look for MCS-certified brands for reliability.

Can Solar Panels Power My Home Entirely on Cloudy Days?

On heavily overcast days, solar panels may not cover all your energy needs, producing 10-25% of normal output. A battery or grid connection ensures uninterrupted power. 

To get a better idea of what you can realistically run during lower-output conditions, check out our guide on what appliances can be powered by solar panels.

Final Thoughts

Solar panels are a reliable and cost-effective choice for UK homeowners, landlords, and commercial property managers, even in cloudy conditions. By generating electricity from daylight, they deliver savings and reduce carbon emissions year-round. 

Optimising panel orientation, investing in high-quality systems, and adding a battery can maximise benefits, while government schemes like ECO4 and SEG make solar more affordable. 

With the UK’s commitment to net zero and rising energy costs, now is the perfect time to explore solar energy.