Do Solar Panels Work When It’s Cloudy? The Surprising Results of a Winter Experiment
If you’ve considered going solar, but you live in a place with long, snowy winters, you have probably wondered, "Do solar panels even work when it’s cloudy or during winter?" This is a really common question, as the thought of long months of overcast skies would make anyone think twice about investing their hard-earned money into solar equipment that might only work for half of the year.
But contrary to popular belief, solar panels can generate power year-round, even on some of the cloudiest and snowiest of days. To prove this fact, we went outside to do some solar experiments on a really cloudy day right after a major snowfall.
Want to discover the results of our real-world testing, keep reading!
So, Do Solar Panels Work in Cloudy Weather?
It’s a widely held belief that if you live in an area with regular cloud cover and harsh winters, going solar is a bad investment because your panels won’t generate enough power for you to see any serious returns. However, this is actually a bit of a myth.
When you think about it, if the sunlight is bright enough that you’re able to see during the day, doesn’t that mean that there’s sunlight that solar panels will be able to use to generate electricity? Sure, thick cloud coverage does block some sunlight, but light still penetrates the clouds, otherwise you wouldn’t be able to see. So, the reality is probably more that solar panels work on cloudy days, but not to their peak potential. This means it’s more of a question of efficiency, rather than whether they work at all.
This sounds logical in theory, but we wanted to test this out for ourselves. To do so, we tested different types of solar panels in various conditions. This included testing them on a winter day with extremely thick cloud coverage, as well as a second day winter day with clear blue skies. Let’s take a closer look at these tests.
The Setup for the Tests
For our tests, we wanted to make sure that we weren’t using some over-the-top solar array. Instead, we decided to use some basic, entry-level solar equipment that is similar to the type of stuff beginners would be likely to own. So, we used:
Two 100W Jackery Solar Panels
Two EcoFlow DELTA Pro Power Stations
Two 200W Rich Solar Solar Panels
One Jackery Explorer 1000 PLUS Power Station
To kick off the experiment, we plugged the 100W Jackery solar panels into the two fully-drained EcoFlow DELTA Pros. Since both units had 0% battery power remaining, we figured they’d start registering a charge right away, even though the cloud coverage was really thick. The results were a little different than our expectations.
The Initial Results: Nothing... At First
Even though the solar panels were plugged into the two EcoFlow Delta Pro Power Stations, neither power station registered any sort of input. This definitely wasn’t a connection issue, as the display screen on the Delta Pros even showed the symbol that indicates you are connected to solar panels, but no power was coming in. This situation was a bit frustrating, but for the purpose of our experiment, it was actually perfect. It replicated a realistic scenario for people hoping to run a smaller solar panel setup on a cloudy day.
While solar panels will generate power with any amount of sunlight exposure, they need a certain amount of it to produce a high enough voltage to meet the minimum power requirements of a power power station. In this case, the panels weren’t producing the 11 volts required for an EcoFlow Delta Pro to start recognizing a solar input. Basically, the 100W panels we were using simply couldn’t reach that voltage under heavy cloud cover. So, while they were generating power, it wasn’t enough to work with the specific type of power stations we were hoping to charge.
Second Attempt: Switching to 200W Solar Panels
The 100W panels didn’t work with the cloud coverage, but we didn’t give up there. After swapping the 100W panels for two 200W solar panels from Rich Solar, we saw immediate results.
The Delta Pros both registered an input, and we started generating enough electricity to charge their internal batteries! This happened because the larger surface area of the 200W panels allowed them to produce a higher voltage, surpassing the 11-volt threshold needed to charge a power station the size of an EcoFlow DELTA Pro.
So, it’s not that the clouds were preventing the solar panels from generating power, it’s that the power station we were using had too high of a voltage rating for running low-wattage solar panels on a cloudy day.
Monitoring the Input on a Cloudy Day
We left the 200W solar panels and DELTA Pros out for an hour to generate and store as much solar power as possible. We checked the input levels roughly every 10 minutes, and the results were surprisingly consistent.
Both EcoFlow Delta Pro units were pulling in about 40 to 47 watts of power every time we went out to check. To make sure the 100W solar panel wasn’t completely useless on a cloudy day, we left it out and connected it to a Jackery Explorer 1000 PLUS Power Station, which has a lower voltage requirement to the much larger EcoFlow DELTA Pro. The Jackery 1000 PLUS was consistently getting around 22 watts from that small 100W foldable panel, even in the same cloudy conditions.
Considering the thick cloud cover and cold winter temperatures, these results were actually better than we expected. Typically, on days with the type of partial cloud coverage you tend to get during the fall or spring, you’d expect even better performance, but during our test, the thick winter clouds significantly reduced sunlight. Still, both the 100W and 200W panels worked!
Testing with Blue Skies
We wanted to run a bit of a control to see just how big of an impact the cloud coverage had. Luckily, the next day we had completely blue skies, even though it was still the middle of the winter.
Unsurprisingly, without the heavy cloud cover, the panels performed much better. One of the 200W solar panels, now more strategically angled against the side of the house to capture more sunlight, was able to pull in 120 to 150 watts, a major improvement from the 40 to 47 watts we saw on the cloudy day.
For comparison, in the middle of summer with the same setup, these panels can typically produce around 180 to 185 watts. So, you’re not talking about a huge reduction in efficiency if you’re running solar panels in the winter if you have blue skies.
As for the cloudy conditions, while the clouds and the low angle of the winter sun cut down the efficiency, it’s still impressive to see the panels generating around 20-25% of their rated output on a cloudy day in the dead of winter. Basically, it busts the myth that solar panels don’t work when it’s cloudy, or in the dead of winter.
The Big Takeaway: Solar Panels Do Work on Cloudy Days!
The experiment shows that yes, solar panels still work on cloudy days, but the output will be lower compared to clear, sunny conditions.
In our real-world test, we saw about 20 to 25% of the rated output on a day with seriously thick cloud coverage, which is still usable power, especially if you have a bigger solar panel array. Larger panels or more panels combined together are likely to keep your power stations charging even in less-than-ideal conditions.
Plus, if you get lucky and get a few bright winter days in a row, you can almost pull in the same amount of power that you would on a sunny day in the middle of the summer.
A Quick Note on Solar Panel Ratings:
If you’re new to solar panels, you might just assume that they always generate the amount of power they’re rated for. For example, a 100W solar panel would always generate 100 watts if it's running, and a 200W solar panel would always generate 200 watts.
The truth is, solar panels are rated according to Standard Test Conditions (STC), which refers to the ideal laboratory conditions under which the panel’s performance is tested. These conditions include perfect sunlight exposure, an ideal temperature of 25°C (77°F), and a specific air mass that mimics the Earth's atmosphere in ideal circumstances. Essentially, it’s a best-case scenario for power generation.
But, as you can probably guess, real-world conditions—like temperature variations, the sun’s angle, and cloud cover—differ drastically from STC. So, while a panel might be rated for 100 watts under STC, it’s rare to see that flawless output in a typical outdoor environment.
Still, the higher the rating, the more power your solar panels are capable of generating, and the more power they’ll be likely to pull in, even in the dead of winter.
Our Final Thoughts: Solar is a Worthwhile Investment
While the sun's angle and cloud cover impact how much power your solar panels will generate, our tests show that even on the cloudiest, coldest winter days, those same panels will still produce electricity.
This might not be the peak efficiency you’d get on the type of perfect summer day that would have you headed to the beach, but it’s far from useless. If you're in an area with long winters or you regularly get cloudy days, having a larger solar array or investing in more efficient panels can help you make the most of solar power year-round.
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