---
title: "Can Solar Panels Still Generate Power on Cloudy Days?"
canonical: "https://solarpanelgreen.com/how-well-do-solar-panels-work-on-cloudy-days/"
author: "David Vance"
published: "2026-10-28T11:00:00+00:00"
modified: "2026-09-25T08:56:45+00:00"
language: "en-US"
site: "Solar Panel Green"
description: "You've been wondering whether solar panels are even worth it when the sky turns gray. It's a fair question. After all, the image of a solar panel usually…"
categories: "Solar Panels"
attribution: "Solar Panel Green (https://solarpanelgreen.com/)"
---

# Can Solar Panels Still Generate Power on Cloudy Days?

You've been wondering whether solar panels are even worth it when the sky turns gray. It's a fair question. After all, the image of a solar panel usually involves bright sunshine, blue skies, and a meter spinning backwards.

 

But the reality is more interesting. In our research, **how well do solar panels work on cloudy days** comes down to three factors: the thickness of the clouds, the type of panel you own, and a temperature twist that might surprise you.

 

Manufacturer specifications tell us that modern photovoltaic panels still generate electricity from diffuse light. Even under heavy overcast, a typical residential system produces 10 to 25 percent of its rated capacity. The key insight is that solar panels don't need direct sunlight; they need light.

 

And light, even scattered through clouds, still reaches the panel surface. Let's walk through exactly what changes, why it matters, and whether your system will keep your lights on when the weather turns.

 

## Why This Isn't a Simple Yes-or-No Answer

 

If you've ever asked a solar installer "how well do solar panels work on cloudy days" and got a vague shrug, there's a reason. The answer depends on a handful of variables that shift day to day, even hour to hour. It's not a flat percentage you can stick on a chart.

 

Think of it this way: your panels are light collectors, not heat collectors. Direct sunlight delivers the most photons per square inch. But clouds scatter those photons, bouncing them in different directions.

 

Your panels can still capture them, just less efficiently. The thickness of the cloud layer is the biggest lever. A thin, wispy overcast might let 70 to 80 percent of the light through.

 

A thick, dark nimbostratus ceiling could drop that number to 10 percent or less.

 

The decision tree we'll work through later starts with one simple question: what kind of clouds are above you right now? From there, we'll branch into panel technology, temperature effects, and your specific energy needs. The goal is to give you a practical tool, not a textbook answer.

 

## Quick Answer

 

Solar panels generate 10 to 25 percent of their rated power under thick clouds. Light overcast allows 50 to 80 percent output. Panel temperature drops on cloudy days, which helps efficiency.

 

Net metering credits can offset low-production periods. Modern panels work fine in overcast climates.

 

## The Three Cloud Types That Change Your Output (and How to Spot Them)

 

![cloud cover types](https://solarpanelgreen.com/wp-content/uploads/2026/07/cloud-cover-types-mruivhyj.jpg)

 

Image source: Bing (Web (fair-use with source credit))

 

You don't need a meteorology degree to estimate your solar output. You just need to look up and identify which cloud family is overhead. Each one affects your panels differently.

 

**Cirrus clouds** are thin, wispy, high-altitude streaks. They look like someone dragged a comb across the sky. These clouds let most sunlight through.

 

Expect 70 to 90 percent of normal output. Your panels barely notice them.

 

**Stratus clouds** are the gray, uniform blanket that turns the entire sky the color of wet concrete. These are the classic overcast. They scatter light heavily.

 

Output typically drops to 10 to 30 percent depending on thickness. This is the scenario that worries most solar shoppers, and it's the one we'll focus on.

 

**Cumulus clouds** are the puffy cotton balls. On a partly cloudy day, you get alternating bursts of full sun and deep shadow. This creates a roller coaster for your inverter: output surges when the sun breaks through, then plunges.

 

Microinverters handle this fluctuation better than string inverters.

 

Image source: Bing (Web (fair-use with source credit))

 

**Nimbostratus clouds** are the heaviest rain-bearing layer. They are dark, thick, and low. Under these, output can fall to 5 to 10 percent.

 

If you live in the Pacific Northwest or the UK, this is your winter reality. The good news is that these days are relatively rare in most climates, and they usually don't last more than a day or two.

 

## How Your Panel Type Affects Low-Light Performance

 

Not all solar panels are born equal. If you're shopping for panels in a cloudy region, the technology inside the frame matters a lot. Here's the breakdown.

 

**Monocrystalline panels** are the most efficient overall. They use single-crystal silicon cells. Their uniform structure lets them capture scattered light better than polycrystalline panels.

 

Most premium residential panels on the market as of 2026 are monocrystalline. If you live somewhere with frequent overcast, these are your best bet.

 

**Polycrystalline panels** use multiple silicon crystals fused together. They are slightly less efficient and tend to perform worse in low light. However, they are cheaper.

 

If your budget is tight and your climate has long sunny stretches, polycrystalline can still work.

 

**Thin-film panels** (like cadmium telluride or CIGS) have a reputation for better low-light performance. That's partially true. In lab tests, some thin-film panels maintain higher output under diffuse light compared to crystalline silicon.

 

The trade-off is lower overall efficiency and a larger footprint. You need more roof space to hit the same wattage rating.

 

![panel type comparison low light](https://solarpanelgreen.com/wp-content/uploads/2026/07/panel-type-comparison-low-light-mruivjes.webp)

 

Image source: Bing (Web (fair-use with source credit))

 

Our research shows that for most homes, modern monocrystalline panels with a high temperature coefficient (we'll get to that next) are the smartest choice for cloudy climates. They offer the best balance of low-light performance, efficiency, and warranty coverage.

 

If you want a deeper dive into panel construction, our guide to the types of solar panels covers each technology in more detail.

 

## The Temperature Twist: Why Cooler Clouds Can Boost Voltage

 

Here's the counterintuitive part. Solar panels are tested at 25 degrees Celsius (77 degrees Fahrenheit). As the temperature rises above that, panel efficiency drops.

 

This is called the temperature coefficient, usually expressed as a percentage loss per degree Celsius above 25.

 

Most panels have a temperature coefficient between -0.3 percent and -0.5 percent per degree Celsius. That means on a blazing 40 degree Celsius summer day, a typical panel loses about 5 to 7 percent of its rated output just from heat. The panels get less efficient even though the sun is brighter.

 

Now think about a cloudy day. The temperature is lower, often 15 to 20 degrees Celsius. That's below the 25 degree reference point.

 

The panel operates in a cooler range, so its voltage is actually higher than the rated value. This effect partially offsets the light loss from the clouds.

 

It's not a huge gain, maybe 3 to 5 percent improvement in voltage. But it means your panels are working more efficiently on a cool, gray day than on a scorching summer afternoon. That's a fact most people don't know until they check the numbers on their monitoring app.

 

The combined result is that a cloudy but cool day can still deliver usable power, especially if the clouds are thin or broken. The temperature twist is a real, measurable advantage that makes solar more viable in overcast climates than many people assume.

 

## Decision Tree: Should You Expect Enough Power Today?

 

This is where we turn theory into action. The question isn't "do solar panels work on cloudy days?" It's "will I have enough power right now?" Work through these four steps in order. Each step narrows the answer for your specific situation.

 

### Step 1 – Check Your Peak Sun Hours by Region

 

Peak sun hours (PSH) measure the equivalent number of full-sun hours your location gets per day. The National Renewable Energy Laboratory (NREL) publishes maps showing average PSH across the US. A place like Phoenix gets about 6.5 PSH in December.

 

Seattle gets around 1.5. That difference matters more than any single cloudy day.

 

You can look up your average monthly PSH for free using the [NREL PVWatts Calculator](https://pvwatts.nrel.gov). Enter your address. The tool shows the average daily solar radiation for each month.

 

Use the worst month (typically December) as your baseline for cloudy climate planning.

 

### Step 2 – Identify Today's Cloud Cover (Thick vs. Thin vs. Mixed)

 

Look up. If you see a solid gray blanket that hides all sun shape, you are under thick overcast (nimbostratus). Expect 10 to 25 percent of rated output.

 

If you see thin haze with faint sun disc visible (cirrostratus), expect 50 to 80 percent. If you see broken clouds with blue gaps (cumulus), expect wide swings but an average of 60 to 90 percent.

 

Weather apps report "cloud cover percentage." Use that as a rough guide. 100 percent cover with dark base equals the low end. 50 percent with high clouds equals the mid range.

 

### Step 3 – Estimate Your Real-Time Output (10%, 50%, or 80%?)

 

Now combine your panel type and cloud condition. A monocrystalline system under thick overcast lands near 20 percent. A polycrystalline system under the same clouds might drop to 15 percent.

 

Thin-film panels can sometimes hold 25 percent.

 

Multiply your system's rated capacity (in kilowatts) by the percentage you estimated. A 6 kW system under thick overcast produces roughly 1.2 kW. That is enough to run a refrigerator, lights, and a few electronics, but not your air conditioner or electric water heater.

 

### Step 4 – Decide: Run from Solar, Use Battery, or Draw from Grid?

 

If you are grid-tied, the decision is automatic. Your system feeds whatever it produces into the house. Any shortfall comes from the grid.

 

Net metering credits from sunny days offset the cloudy ones. You do nothing.

 

If you are off-grid with batteries, check your state of charge. If the battery is above 50 percent and the clouds are light, run normally. If the battery is below 30 percent and the forecast shows more clouds, shift heavy loads to later.

 

Prioritize charging devices and refrigeration. Postpone laundry and dishwashing.

 

If you have a hybrid system with a generator, let the batteries drain to 20 percent before firing the generator. That maximizes solar harvest even on weak days.

 

![decision tree solar output](https://solarpanelgreen.com/wp-content/uploads/2026/07/decision-tree-solar-output-mruivk6q.jpg)

 

Image source: Bing (Web (fair-use with source credit))

 

## How to Size Your System for a Cloudy Climate (Worst-Case Month Math)

 

Most solar installers size systems based on annual usage. That works fine for sunny climates. For cloudy regions, you need to size for the worst month.

 

Otherwise you face a big utility bill in December.

 

The math is straightforward. Take your monthly electricity usage in kilowatt-hours. Divide by the peak sun hours for your worst month.

 

That gives you the minimum system size in kilowatts.

 

Example: your home uses 900 kWh per month. In December your location averages 2.5 PSH. 900 divided by (2.5 x 30) equals 12. That means you need a 12 kW system to cover December usage entirely.

 

A 6 kW system sized for annual average would only produce half your December needs.

 

The trade-off is cost. A larger system costs more upfront. But in a cloudy climate, the extra panels pay for themselves through avoided grid purchases.

 

Our solar panel buying guide walks through the full cost calculation.

 

Manufacturer datasheets also list "low-light performance" in their spec tables. Look for panels with a high current output at low irradiance (200 W/m² test conditions). That number tells you how the panel behaves under clouds.

 

## Common Mistakes That Kill Cloudy-Day Performance (and How to Fix Them)

 

**Mistake 1: Ignoring partial shading from trees.** A single branch throwing shade on one panel in a string can drop the whole string's output. That effect is worse on cloudy days because the total light is already low. Fix: trim trees seasonally or install microinverters to isolate each panel.

 

**Mistake 2: Assuming rain cleans the panels.** It doesn't. Clouds bring moisture, but rain often leaves dirt streaks that block light. On cloudy days, dirty panels lose even more output.

 

Fix: rinse panels twice a year with a hose. Use a soft brush if needed.

 

**Mistake 3: Using an undersized inverter.** Some inverters clip peak production but also underproduce in low light. A good inverter maintains high efficiency even at partial load. Fix: check your inverter's European Efficiency rating.

 

Look for values above 96 percent.

 

**Mistake 4: Setting the wrong panel tilt angle.** Panels tilted for summer sun catch less diffuse winter light. Adjust tilt seasonally if your mounting allows. A steeper tilt (60 degrees) in winter captures more low-angle clouds.

 

**Mistake 5: Ignoring the snow factor.** Snow blocks all light. But snow slides off tilted panels quickly on sunny days. On cloudy days, snow can linger.

 

Fix: install panels at a tilt of at least 30 degrees. Avoid ground-mounted arrays in heavy snow regions unless you can brush them.

 

## Pros and Cons of Solar in Overcast Regions (Honest Trade-Offs)

 

| Pros | Cons |
| --- | --- |
| Panels produce some power every daylight hour, even under clouds | Lower total annual output compared to sunny regions |
| Cooler temperatures improve panel efficiency | Longer payback period, typically 10 to 15 years vs 7 to 10 |
| Net metering credits smooth out seasonal dips | Requires larger system size to cover winter usage |
| No extreme heat degradation risks | More panels needed, higher upfront cost |
| Consistent diffuse light reduces angle sensitivity | Snow accumulation can block production for days |

 

For most homeowners in overcast regions, solar still makes financial sense. The key is honest expectations. You won't zero out your electric bill every month.

 

But over a full year, the savings add up. The advantages and disadvantages of solar panels are well documented, and the conclusions hold for cloudy climates too.

 

State and federal incentives help close the gap. The federal Investment Tax Credit (ITC) still offers a 30 percent deduction as of 2026. Combined with net metering in many states, the math works.

 

## Real Scenarios: Seattle vs. Phoenix vs. London – The Numbers

 

Let's look at real numbers. We compared three cities with drastically different cloud patterns. All numbers assume a 6 kW system with monocrystalline panels and microinverters.

 

| City | December PSH | Estimated December Output (kWh) | Typical December Home Use (kWh) | % of Use Covered |
| --- | --- | --- | --- | --- |
| Phoenix, AZ | 6.5 | 1,170 | 1,000 | 117% |
| Seattle, WA | 1.5 | 270 | 900 | 30% |
| London, UK | 1.2 | 216 | 800 | 27% |

 

Phoenix overproduces even in December. Seattle covers only 30 percent of December usage. London is similar.

 

But look at the annual picture. Seattle gets about 4.0 PSH on average across the year. That means a 6 kW system produces roughly 8,760 kWh annually.

 

A typical Seattle home uses around 10,000 kWh. The system covers 87 percent of annual usage.

 

![cloudy region solar production comparison](https://solarpanelgreen.com/wp-content/uploads/2026/07/cloudy-region-solar-production-comparison-mruivkk3.jpg)

 

Image source: Bing (Web (fair-use with source credit))

 

The gap in December is real. But net metering credits from summer overproduction fill the winter deficit. In Seattle, net metering credits at retail rate make the system cash-flow positive over the year.

 

London has less favorable net metering, but solar still cuts the bill significantly.

 

The takeaway: don't judge a system by December alone. Run the annual numbers. If your climate has decent summer sun, the cloudy winter months are manageable with net metering and proper sizing.

 

## Expert Tips for Maximizing Generation on Gray Days

 

**Adjust your panel tilt if you can.** A steeper angle (50 to 60 degrees) captures more diffuse light from the low winter sun. Fixed-roof systems may not allow this, but ground mounts and some adjustable roof racks do.

 

**Use a monitoring app to track real-time output.** Apps like Enphase Enlighten or SolarEdge show exact wattage. Compare cloudy day numbers to clear day baseline. A sudden drop below 10 percent might mean a dirty panel or wiring issue.

 

**Shift high consumption to midday.** Cloudy days often have a brief brighter window around noon. Run your dishwasher, washer, or EV charger then. Your panels produce peak power between 11 a.m. and 2 p.m. even under clouds.

 

**Consider bifacial panels.** These capture light from both sides. On overcast days, reflected light from the ground adds to output. Bifacial panels can gain 5 to 15 percent more energy in snowy or reflective environments.

 

## Net Metering & Batteries: Your Backup Plan for Cloudy Weeks

 

Net metering is your best friend in a cloudy climate. Your utility credits you at retail rate for excess power you send to the grid during sunny months. You draw those credits back in winter.

 

The result is a near-zero annual bill if your system is sized correctly.

 

Batteries help if your net metering policy is weak or if you are off-grid. A 10 kWh battery (like the Tesla Powerwall or LG Chem RESU) can run essential loads for one to two cloudy days. Pair it with a larger array to recharge faster when the sun returns.

 

Check your utility's net metering cap. Some states limit the system size or credit rate. If your utility offers time-of-use rates, charge your battery during off-peak hours and use it during peak evening hours.

 

That strategy works even on cloudy days.

 

If you want to understand the broader picture, our advantages and disadvantages of solar panels article covers net metering trade-offs in more detail.

 

## Final Decision Guide: Is Solar Worth It Where You Live?

 

Ask yourself three questions.

 

**Do you have net metering at retail rate?** If yes, solar works in any climate. The summer credits cover winter deficits. If no, you need a battery or a larger array to make the math work.

 

**What is your winter peak sun hours?** Below 2.0 PSH in December means you need a big system. Above 3.0 PSH means standard sizing works. Check NREL PVWatts for your address.

 

**Can you install panels at a 30 degree tilt or steeper?** Steeper tilts shed snow and catch low winter sun. Flat roofs or low slopes hurt cloudy day performance.

 

If you answered yes to all three, solar is a sound investment in your location. If you answered no to two or more, it still might work but expect a longer payback. Our solar panel buying guide can help you run the full numbers.

 

## Frequently Asked Questions

 

### Do solar panels work at night on cloudy days?

 

No. Solar panels need light to generate electricity. They produce zero power at night regardless of cloud cover.

 

Batteries or grid power cover nighttime usage.

 

### How much power do solar panels produce on a cloudy day?

 

Thick overcast yields 10 to 25 percent of rated capacity. Light overcast yields 50 to 80 percent. Partly cloudy with breaks can reach 80 to 90 percent.

 

A 6 kW system under thick clouds produces roughly 1.2 kW.

 

### Should I clean my solar panels after a cloudy stretch?

 

Yes. Rain does not fully clean panels. Dust and pollen accumulate.

 

A simple rinse every six months improves output by 5 to 10 percent. Use a soft brush and deionized water if possible.

 

### Can solar panels work in rainy climates like the Pacific Northwest?

 

Yes. Seattle and Portland have high solar adoption. Annual production is lower than Phoenix, but net metering and federal incentives make the economics work.

 

The key is proper system sizing for winter months.

 

### Do thin-film solar panels work better on cloudy days?

 

Thin-film panels (CdTe, CIGS) perform slightly better than crystalline silicon under diffuse light. However, they have lower overall efficiency and require more roof space. For most homes, modern monocrystalline panels offer the best balance.

 

### Will a battery help on consecutive cloudy days?

 

Yes. A 10 to 13 kWh battery powers essential loads for one to two days of heavy overcast. Pair it with a larger array to recharge faster.

 

Without battery, you draw from the grid when production drops.