Mon. Jun 24th, 2024

Credit to Dave Llorens – from his article in – Reprinted here October 27, 2017 –

Solar panels generate the most electricity on clear days with abundant sunshine (not surprisingly). But, do solar panels work in cloudy weather? Yes… just not quite as well. On a cloudy day, typical solar panels can produce 10-25% of their rated capacity. The exact amount will vary depending on the density of the clouds, and may also vary by the type of solar panel; some kinds of panels are better at receiving diffuse light. SunPower solar cells, for example, have been designed to capture a broader range of the solar spectrum. By capturing more red and blue wavelengths, their solar panels can generate more electricity even when it’s overcast.

Ultraviolet light also reaches the earth’s surface in abundance during cloudy days (if you’ve ever been at the beach when it’s cloudy and gotten a sunburn, you’ve experienced this firsthand). Some solar cells are in development that can capture UV rays, although these are not out on the market yet. Even with a standard solar panel on a cloudy day, though, you will be able to generate some power when it’s daylight. The same thing is true in foggy weather. If you live in a city with frequent fog, like San Francisco, you’ll still be able to generate electricity when the fog rolls in.

One cloudy day isn’t as important as the amount of sunshine over a full year…

When you’re looking at how solar power can help you save money on your electric bill, you’ll be considering how much sunshine you get over an entire year, not any particular day. If you’re generating more power than you need, your electric company will look at what you’ve produced over a full year as they calculate how much to pay you.  The good news is that even if you live in a city that isn’t known for its sunshine, you likely still get enough bright light over a year that solar power can make sense for you. Some of the places with the most installed solar, in fact, aren’t known for their sunshine.

Cloudier locations are still a good match for solar

Germany gets only about as much sunshine as the state of Alaska, but Germans have successfully installed about 25 gigawatts of solar power– half of the entire world’s supply. Portland, Oregon is known for its rainy, dreary winters, but is another good location for solar power: over a full year, despite the winter weather, Portland gets as much sunshine as the average U.S. city. Cities like Portland also have slightly cooler weather than average, which is an advantage for solar panels. Because of the electronics inside, solar panels work best when they aren’t too hot. In a city with extreme summer heat, solar is a little less efficient, which is part of the reason why solar panels in cloudy San Francisco can actually produce more power over a year than the slightly sunnier, hotter city of Sacramento.

A silver lining to that cloud: how the “edge of cloud” effect can produce more solar power than a sunny day

If you have solar panels and keep a close watch on your power output, you may have noticed a strange phenomenon: on a partly cloudy day, it’s possible to exceed your solar system’s power rating and produce more power that you could on a sunny day. Known as the “edge of cloud” effect, this happens when the sun passes over the outer edge of a cloud, magnifying the sunlight. The intense light causes your solar system to boost power output temporarily, which can help balance out losses from full cloud cover. Solar installers typically select system components that can handle temporary power boosts of this nature (similar effects can occur when sunlight is reflected off snow or water). If you live in a city with frequent partly-cloudy weather, like Seattle, you may choose to install an over-sized solar inverter to take the best advantage of these power boosts. Sign up with us to learn more.

So, bottom line – do solar panels work in cloudy weather?

Yes, yes they do. But only 10-25% as well. However – this doesn’t matter, what matters is how much sun you get year-round. Cloudy days will come and go, but on the average, it’s not going to affect the return on investment of solar panels at all.



7 thoughts on “Do solar panels work in cloudy weather?”
  1. Homeowners with decent credit can generally purchase a grid-tied system with a monthly expense of less than what they’re paying for electricity.

    Although the Tesla power wall is an option for some people now, soon you will see lithium ion batteries coming down as electric prices continue to rise.

    Within a couple of years, new type of lithium ion battery will be hitting the market. These new batteries far surpass the current capacities of current Lithium-ion batteries and should be half price as well.

    As solar power becomes more mainstream in the United States, you should expect electric rates to rise proportionally as they have in Australia and in Hawaii.

    More and more you should see the Advent of the micro grid. This is where a community shares the cost of energy production storage and distribution.

  2. Thanks for posting this story.

    As an advocate for solar power, and one who’s followed the industry for decades, as the technology has come more and more to the mainstream, I’m very pleased to know that the economic advantage of solar power has finally put it into the mainstream, allowing homeowners and business-owners the ability to generate clean, renewable energy on their own roofs and land that competes with the utility.

    Although the economic advantage of “going solar” varies quite a bit, it’s easy to find out just how much you’d save by employing solar power. The more you spend on energy, the higher is the percentage that you will save. This is due to what we call “soft costs” that are not directly related to the (falling) cost of the panels themselves, and the high cost of permitting, labor, etc.

    Considering that solar is accepted (per this story) as working fine in Portland and Sacramento, and that solar works better in cool weather (not only with more sunny days), let’s compare Crescent City to the other cities for these criterion, shall we?

    City Number Sunny Days Aver. Annual Temp (high/low/average)
    San Francisco 259 63.8 / 50.8 / 57.3
    Sacramento 269 73.6 / 48.3 / 60.95
    Portland 144 63.3 / 45.7 / 54.5
    Crescent City 182 59.6 / 44.3 / 51.95
    * Data compliments of Google

    Based on the comparison, an argument can be made that a solar power system installed in Crescent City will actually outperform the same size system in either Sacramento or Portland.

    Because of this, Crescent City might actually have an advantage over all these other cities. Indeed, the science cited indicates that Crescent City is at least on-par with these other locations, where solar power is immensely popular, and growing faster with every passing day, sunny or otherwise.

    Perhaps then the actual reasons Crescent City doesn’t have an exploding solar market is due only in part to the common misconception regarding cloudy weather, and more likely due to:
    * A narrow hwy 101 & 199 corridors which add cost to sales efforts
    * Energy from PP&L is, on average, somewhat less costly than energy from PG&E
    * The county’s small relative population and density compared to other counties

    Thanks for learning about solar power.

    I’m quite confident as the facts are exposed, you’ll be seeing more and more solar power installed throughout Crescent City.

    1. EXCELLENT POST! Thanks!

      I am also an advocate for solar and have been encouraging people to look into it, but being careful as there are a lot of “solar sharks” out there who are trying con people into bad deals.

      When talking solar, I like to divide solar into two main types of systems: Off grid and Grid-tie systems. The typical system is grid-tie. When discussing solar systems for off grid, I specifically call it “Off grid solar system”. This helps me make that distinction.

      A grid-tie system is a cleaner install but as far as i’ve learned, it does not actually provide power to your home during power outages. I like the off-grid type because i don’t need to have grid power to use it. It is independent from the grid, however the downside is the requirement for batteries and various other electronics that can get quite expensive, like a quality pure-sine power inverter. I use very little in the way of electronics and use very little power, meaning off-grid systems are ideal for me. (I also don’t watch TV and I like to do laundry by hand. I use a Macbook computer which has a very long battery life as well)

      In addition to solar, there is the Powerwall by Tesla. It is a whole house battery that provides power automatically during peak usage time and absorbs power to store when power is cheapest. How many people do their laundry during night to avoid the costs of using the machines in the day? I know quite a few!

      The last time I checked you can buy a Tesla Powerwall for around $3,500. The major advantage on top of cost cutting which will help justify the cost to most people is the fact that this removes the need for a short term whole house generator. That alone can cost more than the powerwall to install. For extended power outages, a generator is still advisable, however.

      For people building their homes, check into “solar tubes” as an option where Windows are not. They bring light into a home from the rooftop down into ceiling. The primitive version of this can be found in 3rd world countries where poverty is rampant and it’s as simple as filling a clear soda bottle with water and installing it through the ceiling so that it sticks out the roof. This works very well for bringing outside light in.. thus saving the need for excessive lighting expenses. The advantage of solar tubs is that they can be installed after the house is built and you can place each side of the tube where you need it. For example, the outside lense can be installed on a side of a house where light is more abundant, with the tube coming through the attic to where you need that light further away. I have even seen solar tubes used to get light into basements.

      The investment is well worth it in the long run.

      1. Nicholas, With the kind of money that you are talking about in reference to the Powerwall alone, it would seem to limit the market to people who have a relatively substantial income. One thing lacking in terms of cost is what will a modest, yet complete solar system cost a home owner? If I was to be a buyer, with regard to the rather harsh climate we live in, what are the expected maintenance costs per year? Are they factored in when you say “the investment is well worth it”? I am sure you are aware that the financial make up of Del Norte County would make $3500 out of the reach of many of its residents. If the initial cost was substantially north of the $3500, plus yearly maintenance, plus the cost of cleaning the panel surfaces, and the factor of the useful life span of a solar panel, it would seem that the recovery costs from electrical savings just might exceed the useful life span of the panels. One other item that I am curious about is the efficiency of the storage system, the batteries? and their life span, plus their maintenance costs and how much energy efficiency is lost when converting DC power to AC power, or the conversion cost of your appliances from AC consumers to DC consumers? And last but not least, it seems that most installations both here and abroad are that of government entities and not those of private residents or businesses. Is there some kind of correlation between spending tax payer dollars over those spent by private individuals and businesses? The fact that Germany produces only 25 gigawatts and it is half the world’s production, seems to me that solar power research has a ways to go before it will become cost effective for most people. 50 Gigawatts is a relatively miniscule amount of electricity compared with the total electrical use world wide. If it is such a great investment it would seem that the interest would be far greater? What say you, Nicholas?

        1. I went a different way I put in a wood stove my power bill is never over 100.00 so solar would never pay off for me as far as cutting wood I like it gets me out of the house

        2. I actually think anyone with a job can afford it, but they have to be willing to not continue to live a lifestyle of spending all their money as soon as they get it. A couple of easy choices for me include not paying for cigarettes and cable TV. I have never paid for cable TV in my entire adult life. That’s a lot of money not spent.

          Financing cars, mortgaging houses.. or even paying high rent on a place that will never be theirs, that is money thrown away.

          I think that the benefits of solar are only possible if people change their electric usage. In my case I use virtually no electricity other than a fridge to keep food cold (that’s a luxury item for me), keeping my laptop charged and my other electronics like my bluetooth headsets, tablet and phone.

          Then again, I just went back to living in an RV rent free, but this time up top of a mountain near Susanville, CA, with a view overlooking Honey Lake. I have 19 acres all to myself. I work from home as a software developer and the RV I am living in I just spent $1,500 on and in surprisingly excellent condition. If more people would follow my example in life, they too could enjoy huge financial savings and be able to afford the luxury things that could save them later. Imagine living in an RV or trailer off-grid for 5 years rent-free.. take that money that would have been spent on rent and put it into a bank account. Take that cable bill and scrap it, put that money into the bank also. Buy a beater vehicle and drive it until it’s dead and replace it for another cheap beater. The savings over financing alone would be good money that could also be put in the bank.

          Wouldn’t take very long to have the wealth, would it?

          If I would have paid for cable TV at say, $50/mo for the last 18 years of my adult life, that’s getting close to $11k right there. Couple that with cigarettes which were if I remember right somewhere around $3-4 a pack back in 1999 and today they are far higher.. most people I know smoke 1 pack a day. That’s nearly $200/mo for 1 person. Most smokers who have a significant other, well that significant other most likely smokes as well so there’s 400/mo that will eventually lead to health problems and higher health care costs. Most people I know in Del Norte smoke and have cable TV and are financing at least 1 car. These people could afford to change things up a little.

          People might look down at me for being the guy who lives in an RV, but I have a plan in life. I guess i’m not a typical American. Those people can continue to watch the good life on television while people like me get to live it.

          I am sorry I didn’t answer your question more directly.

          1. Not to worry. I suspect that the cost of a solar system for power remain something that tax payer funding is a key component. Otherwise, it would be a far greater component of electrical usage, and quite frankly solar power only accounts for a very small percentage of over all electrical production. Clearly there are some challenges yet to over come for residential and private businesses to main stream solar power as a wide spread source of power.t

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