Do Solar Panels Work on Cloudy Days?Yes — Here's the Real Data
Solar panels produce electricity from all daylight — not just direct sun. Germany gets 30% less sunshine than Boston yet leads Europe in solar. Here is what actually happens to your panels on cloudy, rainy, and overcast days — with real production numbers from New England installations.
Quick Answer
Solar panels produce 10-25% of rated output on fully overcast days and 50-80% on partly cloudy days. This is because photovoltaic cells respond to all visible light, including diffuse light scattered by clouds. Annual production estimates already account for local weather patterns — a system designed for your address factors in every cloudy day you will have.
The Science: How Solar Panels Capture Diffuse Light
Sunlight reaches Earth in two forms. Direct beam radiation travels in a straight line from the sun and creates sharp shadows on clear days. Diffuse radiation is sunlight scattered by clouds, water vapor, dust, and atmospheric particles — it arrives from all directions across the sky.
Clear Day
- 80% direct beam radiation
- 20% diffuse radiation
- Sharp shadows visible
- Panel output: 90-100% rated
Overcast Day
- 0% direct beam radiation
- 100% diffuse radiation
- No shadows visible
- Panel output: 10-25% rated
The key insight: the sky is still bright on a cloudy day. You can read outdoors, drive without headlights, and take photos. That ambient brightness is the diffuse light your panels capture. Photovoltaic cells respond to all photons in the visible spectrum, whether they arrive in a focused beam or scattered through clouds.
The “edge of cloud” effect: When sunlight hits the edge of a passing cloud, the cloud acts like a lens — focusing and reflecting extra light onto your panels. This can briefly push production to 105-120% of rated capacity. These “super-peaks” last seconds to minutes and are regularly captured in monitoring data.
Production Levels by Weather Condition
The table below shows typical output for a 10 kW residential system (roughly 22 panels) under different sky conditions. Values assume peak sun hours and standard equipment.
| Weather Condition | % of Rated Output | 10 kW System Output |
|---|---|---|
| Clear sky, full sun | 90-100% | 36-40 kWh/day |
| Light clouds / haze | 70-90% | 28-36 kWh/day |
| Partly cloudy | 50-80% | 20-32 kWh/day |
| Fully overcast | 10-25% | 4-10 kWh/day |
| Heavy rain / storm | 5-15% | 2-6 kWh/day |
| Snow-covered panels | 0-5% | 0-2 kWh/day |
| "Edge of cloud" burst | 105-120% | 42-48 kWh (brief) |
Important: A “cloudy day” is rarely 100% overcast from sunrise to sunset. Most cloudy days include breaks of sunshine, producing a mix of conditions. Real-world cloudy-day output is often higher than the “fully overcast” row suggests because intermittent sun pushes average production up.
The Germany Argument: Cloudier, Yet #1 in European Solar
Germany is the world's 4th largest solar market with over 80 GW of installed capacity. Berlin receives roughly 1,625 sunshine hours per year — about 38% less than Boston's 2,630 hours. If solar could not work in cloudy conditions, Germany's $100+ billion solar investment would make no sense.
The lesson: solar ROI depends on electricity prices and policy, not just sunshine. High electric rates make every kilowatt-hour you generate worth more. New England's rates ($0.25-$0.32/kWh) rival Germany's, and we get significantly more sun.
| Location | Sun Hours/Year | Avg Electric Rate |
|---|---|---|
| Berlin, Germany | 1,625 | $0.36/kWh |
| London, UK | 1,480 | $0.38/kWh |
| Boston, MA | 2,630 | $0.28/kWh |
| Hartford, CT | 2,520 | $0.27/kWh |
| Portland, ME | 2,480 | $0.27/kWh |
| Providence, RI | 2,550 | $0.29/kWh |
Boston gets 62% more sunshine than Berlin. Even Portland, Maine — the cloudiest New England capital — gets 53% more sun than Berlin. Clouds are not a deal-breaker. Electricity prices are what drive solar economics.
Monthly Production: Typical 10 kW New England System
This table shows how a 10 kW system distributes its ~10,000 kWh annual production across the calendar year. Cloud patterns, day length, and sun angle all factor in. Data averaged from NuWatt installations across eastern Massachusetts, southern New Hampshire, and Rhode Island (2023-2025).
| Month | % of Annual | kWh | Peak Sun Hrs |
|---|---|---|---|
| January | 4.2% | 420 | 3.0 |
| February | 5.5% | 550 | 3.8 |
| March | 8.0% | 800 | 4.5 |
| April | 10.2% | 1,020 | 5.2 |
| May | 11.8% | 1,180 | 5.8 |
| June | 12.5% | 1,250 | 6.2 |
| July | 12.8% | 1,280 | 6.0 |
| August | 11.5% | 1,150 | 5.6 |
| September | 9.0% | 900 | 4.8 |
| October | 6.5% | 650 | 3.8 |
| November | 4.5% | 450 | 3.0 |
| December | 3.5% | 350 | 2.5 |
Summer (May-Aug)
48.6%
of annual production
Spring + Fall
33.7%
of annual production
Winter (Nov-Feb)
17.7%
of annual production
New England State-by-State Solar Performance
Peak sun hours measure the equivalent hours of full-intensity sunlight per day, averaged annually. Even the “cloudiest” New England states get enough sun for excellent solar returns when paired with high electricity rates.
| State | Avg Peak Sun Hrs/Day | Avg Electric Rate | Typical Payback |
|---|---|---|---|
| Massachusetts | 4.5 | $0.28/kWh | 7-9 yr |
| Connecticut | 4.4 | $0.27/kWh | 8-10 yr |
| Rhode Island | 4.4 | $0.29/kWh | 8-10 yr |
| New Hampshire | 4.3 | $0.27/kWh | 9-11 yr |
| Maine | 4.2 | $0.27/kWh | 12-15 yr |
The Cold-Weather Advantage: Panels Work Better When It's Cool
Here is a fact that surprises most homeowners: solar panels are more efficient in cold weather. Solar cells are semiconductors, and like all semiconductors, they generate more voltage when cooler. This is measured by the temperature coefficient — typically -0.3% per degree Celsius for modern monocrystalline panels.
Temperature Coefficient in Practice
Rated at (STC)
77°F / 25°C
Panel nameplate baseline
Hot Summer Day (95°F)
-8% output
Panel surface reaches ~150°F
Cold Winter Day (25°F)
+8% output
Per sun-hour vs summer
On a clear, cold January day at 25°F, your panels produce roughly 16% more electricity per sun-hour compared to a sweltering 95°F July afternoon. The tradeoff is shorter daylight (9.3 hours in January vs 15.3 in June). But per-hour, cold weather is genuinely better for solar. New England's climate is a net positive for panel longevity and per-hour efficiency.
How Net Metering Smooths Out Cloudy Days
Net metering is the mechanism that makes cloudy days essentially irrelevant to your electricity bill. Here is how it works:
Sunny day surplus
On a clear June day, your 10 kW system produces 40+ kWh but you may only use 25 kWh. The extra 15+ kWh flows to the grid and your utility credits your account.
Cloudy day draw
On an overcast day, your system produces 8 kWh but you use 25 kWh. You draw the difference from the grid and your banked credits cover the cost.
Annual true-up
Over 12 months, your total production is designed to match your total usage. Summer surplus offsets winter deficit. Cloudy days are already accounted for.
The result: you do not need every day to be sunny. You need the annual total to cover your annual usage. Net metering makes your system work like a bank account — deposit on sunny days, withdraw on cloudy ones.
Battery Storage for Cloudy-Day Resilience
While net metering handles the economics of cloudy days, battery storage adds physical resilience. A home battery stores solar energy produced during the day for use at night or during outages — particularly valuable during the storms that often bring cloudy weather.
With Net Metering Only
- +Credits banked for cloudy days
- +No extra equipment cost
- −No power during grid outages
- −No self-consumption optimization
With Battery + Net Metering
- +Credits banked for cloudy days
- +Backup power during outages
- +Store solar for nighttime use
- +ConnectedSolutions revenue (MA/RI)
In Massachusetts and Rhode Island, battery owners can also earn $225-$275/kW annually through ConnectedSolutions demand response programs. This revenue shortens battery payback regardless of cloud cover.
Best Panel Technology for Cloudy Conditions
Not all solar panels perform equally in low light. If you live in a cloudier area, choosing the right technology matters:
Monocrystalline PERC
Best mainstream choiceRear-side passivation captures more diffuse photons. 3-5% better low-light performance than standard cells. This is what most quality residential panels use today.
Heterojunction (HJT)
Premium low-light kingCombines crystalline silicon with thin-film layers. 5-10% better in diffuse light. Lower temperature coefficient (-0.26%/C) means even better cold-weather gains. Used in REC Alpha and select high-end panels.
Half-Cut Cells
Reduces internal lossesSplitting each cell in half reduces resistive losses by 75%. Especially helpful in partial shade from passing clouds where some cells produce less than others.
Microinverters (Enphase IQ8)
Panel-level optimizationEach panel operates independently. When a cloud shades one panel, the rest produce at full capacity. String inverters drop the entire string to the weakest panel.
6 Tips to Maximize Solar Output on Cloudy Days
Optimize tilt angle for your latitude
Panels tilted at your latitude angle (roughly 42 degrees in New England) capture the most diffuse light year-round. Flat panels miss oblique-angle diffuse light. Steeper tilt also helps shed snow and rain.
Keep panels clean
Dirt, pollen, bird droppings, and leaf debris reduce light transmission by 2-5%. On cloudy days when light is already limited, every percent matters. Clean panels annually or rely on rain for natural washing.
Choose microinverters over string inverters
Passing clouds create uneven shading across your roof. Microinverters let each panel produce independently, so one shaded panel does not reduce the entire array. This is the single biggest upgrade for cloudy-day performance.
Trim trees and reduce shading
On overcast days, diffuse light comes from all directions — including low angles. Trees that barely shade your panels on sunny days can block significant diffuse light. Trim branches within 20 feet of your array.
Monitor production daily
Use your Enphase, SolarEdge, or other monitoring app to track daily output. This helps you understand your system's real cloudy-day production and catch any issues (failed panel, inverter error) that reduce output.
Size your system for annual usage, not daily
Do not oversize your system to compensate for cloudy days — net metering handles the daily variation. Design for annual kWh match. An oversized system wastes money producing credits you cannot use.
Common Myths About Solar and Clouds
Myth: “Solar panels need direct sunlight to work”
False. Panels convert all visible light — direct and diffuse — into electricity. Even on heavily overcast days, there is enough light to read outdoors, which means there is enough light for solar production.
Myth: “Rain damages solar panels”
False. Solar panels are tested to IEC 61215 standards, including 1-inch hail at 52 mph, salt mist, and 5,400 Pa mechanical loads. Rain is beneficial — it naturally cleans panels and can improve next-day production by 2-5%.
Myth: “Solar only makes sense in sunny states like Arizona”
False. Massachusetts (#3 solar per capita) has higher electric rates than Arizona and competitive payback periods despite fewer sun hours. Solar ROI depends on rates and policy — not just sunshine.
Myth: “Panels produce nothing in winter”
False. Winter production is lower due to shorter days, but panels produce 15-20% of annual output from Nov-Feb. Cold temperatures actually boost per-hour efficiency by 8-10% compared to summer heat.
Frequently Asked Questions
Do solar panels work when it is cloudy?
Yes. Solar panels produce electricity from all daylight, not just direct sunlight. On overcast days, panels produce 10-25% of their rated capacity using diffuse light (sunlight scattered by clouds). On partly cloudy days, panels produce 50-80% of rated output. Even heavy overcast produces some electricity.
How much do solar panels produce on a cloudy day?
On a fully overcast day, solar panels typically produce 10-25% of their rated capacity. On a partly cloudy day, production ranges from 50-80%. Light clouds or haze reduce output by only 10-20%. A 10 kW system rated for 40 kWh on a clear day would produce 4-10 kWh on an overcast day and 20-32 kWh on a partly cloudy day.
If Germany is so cloudy, why does it produce so much solar energy?
Germany gets about 30% less annual sunshine than the New England average, yet it has over 80 GW of installed solar capacity. Solar economics depend on electricity prices and policy, not just sunshine. Germany's high rates (over $0.36/kWh) make solar extremely cost-effective despite clouds. New England has similar high rates ($0.25-$0.32/kWh) and more sunshine than Germany.
Do solar panels work in the rain?
Yes, solar panels work in the rain at reduced output (5-15% of rated capacity). Rain actually helps by washing dirt, pollen, and debris off panel surfaces, which can improve production by 2-5% the following day. Rain does not damage panels — they are built to IEC 61215 standards and withstand heavy rain, hail up to 1 inch, and extreme weather.
Are some solar panels better in cloudy conditions?
Yes. Monocrystalline PERC and heterojunction (HJT) panels outperform standard polycrystalline panels in diffuse light by 5-10%. Half-cut cell designs reduce resistance losses in low light. Microinverters (like Enphase IQ8) optimize each panel independently, so one cloud-shaded panel does not drag down the entire array.
Do solar panels produce more in cold weather?
Yes. Solar panels are semiconductors that become more efficient as temperature drops. With a typical temperature coefficient of -0.3%/degree C, panels at 25 degrees F (-4 degrees C) produce about 8% more per sun-hour than at 95 degrees F (35 degrees C). Cold, clear winter days produce excellent per-hour output — the main winter limitation is shorter daylight, not clouds or cold.
How does net metering help on cloudy days?
Net metering lets you bank excess solar credits from sunny days and use them when it is cloudy. In summer, a well-sized system may produce 30-50% more than you use daily. Those credits carry forward to offset cloudy days and winter months. Over a full year, your system is designed to match or offset your total annual electricity usage.
Should I get battery storage if I live in a cloudy area?
Battery storage is more about outage protection than cloudy-day performance. Net metering already smooths production across days and seasons. However, a battery like the Tesla Powerwall 3 or Enphase IQ Battery provides backup power during grid outages (which often accompany storms). If outage resilience matters, batteries are worth considering regardless of cloud cover.
See How Much Solar Produces at Your Address
Our satellite-based design tool uses your exact location, roof angle, shading, and local weather patterns — including every cloudy day — to estimate year-round production. Get an accurate estimate in minutes.
Get My Free Solar Estimate