What Do Solar Panels Produce On Cloudy Days 

Main two factors for cloudy day production are the cloud deck thickness and time of year. There are many many other factors too. Day 900+ off grid here and on rainy winter days I’m lucky to even get 1kWh total daily production out of my 7kW array. On rainy summer days that number is around 5-6kWh produced. Really need a pyranometer for these types of tests.

I only have 330 watt system. I get about 5% on cloudy days. I use the 3 finger system. Hold up my hand and can count my fingers in my shadow, then I can expect 75-100% of rated output. Otherwise I get very little.

Thanks for the video. I have two systems my main system is 9.4kW and my SolarEdge system is 6.4kW but I don't really monitor it. On the 9.4 kW system I just finished upgrading to bifacial models for a portion of it which is 4.44kW, I just bought 12 more bifacial PV to upgrade my other half of this system because on overcast days the bifacials do better than the standard modules and I live in the western Catskills of NY and we get a lot of overcast days here. I wouldn't think bifacials would give much benefit on roof installs though, mine are on ground mounts, the high point is about 10 feet off the ground and they are at a 42 degree inclination. The thing is that I've noticed that there are different levels of overcast so it's hard to get a good measurement of output. Generally speaking I'd say I get about 1 to 1.3 kW on an average overcast day, the bifacials do help a lot.

Very interesting video! I have 16 cheap 250 watt used san tan solar panels and when I lived in Pueblo (Colorado) they did ok even on a cloudy day. Probably around 30% (of what I would get on a sunny day not standard test conditions numbers) . Wasn't cloudy much and very little humidity or particulates in the air. I am now in south central Oklahoma and on a cloudy day I get about 20%. And tons more cloudy/humid days. Lucky my load is lower here so the system still does pretty good. Not bad for old panels.

Well, you have an enphase system, it would be cool if you just posted a picture of it with "Month" selected that shows each day's generation for 30 days or so. That gives you 30 full-days-generation data points to show people that will include sunny, party cloudy, cloudy, and probably some rainy days too yes? For example, when I look at my brother's system for November, the sunny days run from 21 kWh to 18 kWh as the month progresses, and the cloudy days run mostly in the 13 kWh range with the worst day generating only 3.6 kWh. So at least for his system, the worst day's generation was around 18% of what he would get on a sunny day during November. And the system average for the whole month was considerably better than that. I don't think there is much of a point looking at a few wattage samples. What matters is the whole day's generation.

I have taken a lot of data on solar panel output versus sky conditions. The solar panel rating is based upon idea or slightly better than best-case scenario. The rating assumes the panels are perfectly aimed towards the sun, the sun is directly overhead (high noon), the sky is perfectly clear, humidity is low, the temperature of the panels is +25 degrees Celsius/+77 degrees Fahenheit, the rated power is being measured at the panel terminals, and the panels are brand new. Any kind of cloudiness quickly drops the panel output. For instance, if the day is bright and sunny, with an occasional white puffy cloud passing in front of the sun, panel output drops about 75%. On the maximum end of cloudiness, if a severe thunderstorm is about to strike, panel output drops about 99.5%. In both cases of cloudiness mentioned here, the sun is within +/- 2 hours of high noon. Add to these losses are the system losses: wiring voltage drop, solar controller loss, power inverter loss, battery charge loss (this assumes off-grid, grid-tie would not have the battery and solar controller losses). In short, with off-grid, you get about 50 to 70% of the panel power converted to house power. With grid-tie, it is 80 to 90%.

Industries & youtubers will have you believe this is a Freak & Odd day, in fact is just a Regular day 😳

Hard to calculate with any accuracy because cloud density would cause vastly different current readings.

thats why amorphous solar panels are a better choice... unfortunately , no one sells these panels anymore (lol)

Thanks for the video. I see you created an average for the test points. I am surprised it was so low for a cloudy day. I suppose that means if you get a lot of cloudy days it might mean having to severely oversize the total system.

The issue for some people they made massive investments, and this is not an odd cloudy day, is Just a Regular Day 😳 the Odd & rare day is when it's sunny & not a single cloud in sight How many times that happens in 1 year 🤔

simple solar value calculation. presume 1000kWh annual power for each 1 kW solar installed. Lots of public data, you need to know how to interpret for your area, but this works for almost all latitudes say above 40 degrees. Know your cost of install per watt. Example 10kW instaled for $3/watt = $30,000. Life expectancy if everything works perfectly, 25 years. 25 year mortgage calculator shows $30,000 would be $200/mo for 25 years(depends on rates). If your grid power cost is 10c/kWh and your 10kW system can earn 10,000kWh/yr x .10c/kWh = $1000/yr while annual payments are $2000/yr as shown above. Inverter life expectancy 10-12 years, solar panels degrade making less power every year, solar panels can fail, etc. Payback....if you are cashing in investments that should be earning you at least 6%/yr, I suggest you leave your money invested. And watch out for solar salesmen and their claims.

Not much. Plan accordingly.

Thanks for the info! This explains why solar panels won't work when placed inside my car. Also just in case anyone knows about this: any commercial product that can charge portal power station at low light (e.g. panel put inside car/indoors)? Thanks!

So basically, if you live in the rustbelt such as Michigan, New York or anywhere around here, Minnesota, Wisconsin, etc. etc. these things are worthless because we have 7 to 8 months of cloud cover and barely any sun when the sun does come out in a nutshell a big waste of money

I picked up (2) Rich Solar 200 w panels last year. I did this because i wasn't 100% sure where i was going to put my pa els when i got the system i wanted. I figured I'd play around with 2 cheap panels for a while to help decide what panels i needed where. The absolute best output I've ever seen was 305 watts. In cloudy conditions, I'm getting less than 10 watts.

I have 5.5KW off grid solar inverters, and they word well. NICE!

Hello we have attempted to fix/ upgrade our solar system to accommodate our family to no avail. We are Army Veterans that decided to move totally off grid with our 3 kids. Despite our efforts we have problems when we get very little sunshine. It seems the batteries aren't charged enough to take us through the night. On an average day the sun would have charged our system and the inverter will go into the night displaying 50 volts. However, during a heavy rain we had 2 days ago that started at 9am and lasted all day, we went into the night at 44 volts! By midnight the alarm was sounding on the inverter and the power went off shortly thereafter. We also have this issue when we attempt to turn on the air conditioning...using it too close to sun down can cause the same issue. I was thinking we need a larger battery bank but someone told me I need more panels. Honestly I'm confused. Please help.

So far, My 10.3 kw system has a daily low of 2.0kwh(Nov 21st) and a daily high of 56.6kwh(Aug 19th) since Aug 1st. Huge range. I am starting to hate rainy days, from a Solar generation point of view. The max I have seen so far is 7.1kw, 69% of my system. Thanks for the video.

On a fully overcast day my EcoFlow was showing 0 input on 400w panel. It is about to snow though so when the sun was behind clouds it was very dark thick clouds

This probably shows that installer solar panels are the cheapest ones and don't perform that well in cloudy days, while the other ones are more efficient during those types of days.

my friend,it doesnt matter how small ammount of energy we get from solar panels in winter it is god that we have some energy for free,for me one light builb is fortune iin winter time because i live in forest away from city..

Hi I would like my house mini inverter 5600w installer direct ac plug and play ist possible

thin film panels are better for cloudy conditions...just sayin'

hello ，would you have interested in testing our foldable solar panel ?

Haven't watched the video yet, but I'm staking my response right now: Is it Electricity? I hope it's electricity! Imagine if they made angry spirits, or disturbing smells!

Those were some cool setups! I just got a Tesla system installed last winter and have been having a fun time exploring the app. Out of curiosity I really tried to drill down into what was affecting the maximum output on different days, and in addition to the cloud cover and time of year, I'm pretty sure I've been seeing effects from temperature and even windspeed as well. Very cool stuff!

1/10th - 1/100th of rated power its misarable

What about Polycrystalline vs mono crystalline ?

What are those legs on the 100w panels?

Would linking in parallel instead of series give better results?

4-5%

I was expecting basically zero percent production so better than expected.

I had read in a scientific solar article a year or so ago that a solar panel with good efficiency (21-22% efficient) can produce about 10% of rated power on even a full overcast day so your percentages may be a bit off (low) but you are getting the point that even on a dreary cloudy day the panels can produce power.

on cloudy rainy days I'm lucky to get 20 percent

How about 14.6 kW Bifacial ground mount solar array, EG4 18 k inverter/charger, 32 kWh Lifep04 battery with 2 amp active balancing BMS and a EG3 Chargeverter all for $16.000. and our system still works when the Grid is down.

It is cloudy here today, the highest my panels reached 120Watts, on a sunny day the highs will be around 2200Watts, so that's 5.45%. The maximum my panels can produce is 2700W, so I got 4.4%, so we will call it 5% on a cloudy day, and 82% on a sunny day

🤔 S. Fl. No problem....

you have no idea how the bms works

Good info.

As soon as I saw the video with the clouds and the lighting I made the guess of 8% of rated capacity. Really depends on that power point tracking to some extent, but I was pretty confident in my diy experience to say 8% right off the bat.

EcoFlow Delta Pro? You've got to be kidding. No experienced off gridder is going to use a low cost, high frequency, transformerless inverter charger like a EcoFlow for their residential application. With over 24 years of experience in the inverter repair industry, we know full well that the vast majority of low cost, lightweight, Chinese made, high frequency inverters on the market simply don't last. Especially when powering inductive loads like refrigerators, microwave, ovens, portable air conditioners, power tools or motors. You may be able to start some of these loads when your high frequency solar generator is new, but over time, typically after less than a year of repeated use, powering high inductance loads, your lightweight, high frequency solar generator WILL fail. They simply were not designed for powering inductive loads. That's why the big name brand inverter manufacturers like Schneider Electric, Outback Power, Magnum Energy, Sigineer Power, Victron Energy and others, all use a low frequency topology in their design.

I have a 6kwh (2x3 at 370v) array especially for cloudy weather, a very shallow angle works best, pretty much 10 to 20 degree tilt. It captures maximum diffused sun from the clouds.