Do Solar Panels Work On Cloudy Days?

When it comes to solar panels, there tends to be two camps – those who love solar and those who hate it.

The haters are easy to spot as they’re always talking about how bad the manufacturing of panels is for the environment – as if relentless fracking and burning of coal is somehow better. For an in-depth look at that argument, check out this article.

And while the haters can be willfully blind to certain realities, I have found that some solar fans can be equally as blind.

## Fact ##

Photovoltaics require direct sunlight in order to perform at their best. Any interference, including cloud cover, can greatly reduce power output.

As someone who has lived off-grid since 2015, I can say with confidence, that solar panels do NOT work well on cloudy days.

While it is technically true that they will generate some power in overcast conditions, realistically speaking, it will probably not be enough to power your home.

Let me give you an example.

Our current home-power system, requires roughly 3 hours of good sunlight, in order to operate our house for 24 hours. For those times where sunlight is inadequate, we have a backup generator to assist in charging our batteries.

Today was cloudy.

Consequently, I had to run the generator for 2.25 hours.

In other words, despite the fact that we had 9+ hours of daylight today, we only produced the equivalent of 45 minutes of good sunshine.

This is why I always urge caution for those who would oversell the capabilities of solar panels on cloudy days. There are a host of variables that can influence power output.

For the record, I have seen days where our solar array manages to produce power in less than ideal conditions. But generally speaking, clouds and solar panels are not a good mix.

Types Of Clouds

To understand clouds and their relationship to power generation, it pays to differentiate between the different types of cloud cover.

  • Bright white fluffy clouds, with spots of blue sky in between, have very little impact on our ability to power the house.
  • Precipitation clouds, such as rain or snow, is devastating to power generation.

Remember, photovoltaics require direct sunlight and the more interference there is between the sun and your panels, the less productive they will be.

And it doesn’t have to be just clouds. Fog can completely render your panels inert, as well as, small airborne ice crystals.

I can tell you, there is nothing more puzzling (and extremely frustrating) than having the winter outdoors be bright and sunny, while your solar array – which is capable of producing 7,800 watts – only generating 200 watts.

In this particular situation, the extreme cold formed very small flakes of ice that seemed to hover in the air – essentially acting as miniature mirrors as they interrupted the path of direct sunlight. And while they were virtually impossible to see with the naked eye, they were present enough to render our panels ineffective.

Conclusion

So now that we’ve established that clouds can greatly reduce the output capacity of solar panels, are we to discount solar as a means to power our lives?

Not at all!

I have heard qualified solar installers make the claim that solar in Michigan is just not feasible. This is not so much a fault of the panels, but rather of the precipitation related to the Great Lakes – specifically during the winter months before the lakes have frozen over.

And in truth, it can be brutal! There have been days where our solar array produces no power at all.

But, as we continue to learn from our off-grid adventure, panel technology also continues to improve. The panels that are available today are notably more productive and less expensive to acquire than they were when we went off-grid in 2015.

I am confident, that if we were to take another house off-grid, with the improvements in panels and the knowledge that we have gained, we could reduce our reliance on the backup generator by 50%.

To put that into perspective, our total fossil fuel consumption for a family of three is currently right around 500 gal. of propane – for the entire year. And it’s worth noting that 80+% of that is used by the backup generator.

The overwhelming majority of power we use comes from solar… even in the cloudy winter skies of Michigan. And as technology moves forward, the capacity to produce power is only going to improve.

So while clouds and solar panels do not mix, solar power is most certainly a viable energy solution!