How can I tell if Solar Panels are working effectively?

[Tigermoose]

I have noticed a drop in generation from 2021, but i am thinking it could be just due to yearly differences in sunlight. I live in Southern California. Is there a website or app that shows the sunlight amount per month per year that I could use to help analyze this?

[jm1495]

Were they new in 2021?

Most panels have a an output loss of 2-3%/ year for the first few years until they plateau. Also most solar installers have a generation warranty /guarantee. It might be good to review the install documents.

My system has monitoring at the panel level that I can see the output over a day/week/month/year/ all time.

[Nate79]

Our experience is that there is enough year to year fluctuation that you would need many years of trend to really see the drop in efficiency. We live in Delaware so our sunshine would be different than in California but here is our year to year production from the install year:
2019: year of install
2020:12.23MWh
2021:12.30MWh
2022:12.57MWh
2023: 11.94MWh

As you can see the output increased in its first 3 years and then in 2023 it was down a little bit. It would be interesting if there was a solar output website to compare.

[Tigermoose]

They were on the house when we bought it in 2020. I think they were probably about 3 years old at that time.

If I could just find some kind of historical weather information on cloud cover or available sunlight for my area then I could graph that out and see if there is a correlation to the solar generation of each month/year.

[exodusNH]

They were on the house when we bought it in 2020. I think they were probably about 3 years old at that time.

If I could just find some kind of historical weather information on cloud cover or available sunlight for my area then I could graph that out and see if there is a correlation to the solar generation of each month/year.

Could they need a cleaning?

[cadreamer2015]

Our solar panels generated ~8% less in 2023 than in 2022. Early 2023 was very wet - we finally broke the drought. I’m in San Diego county.

[Tigermoose]

Our solar panels generated ~8% less in 2023 than in 2022. Early 2023 was very wet - we finally broke the drought. I’m in San Diego county.

Yes, I remember that. I am in Temecula. Was 2021 a great year for solar energy?

Also - I'm seeing a severe degradation in generation during July and August. I know some of that is supposed to be due to heat causing poorer solar performance, but is there something with how Southern California Edison accepts energy credits that reduces the amount? Some kind of cap?

[mrc]

I installed my solar system in 2009. I didn't begin recording weekly readings until 2016. So any first- or second years loss had already happened. Every week, I record the cumulative kWh the solar has produced at the inverter, and subtract the last week's reading to obtain the weekly net. I then plot the 4 week average of this weekly production to see how the array is performing. The four week average should smooth out some of the snow covered or extended periods of grey weather. You can see from my graph production is lower in winter and higher in summer. Production has inched downward every year. I wish I had the complete record.




Here's the total kWh produced (actual) each calendar year. The first year is incomplete.

[CloseEnough]

There are monitoring sites that you can use to answer your questions. One is SolarEdge, the one we use. It shows the output of each panel, per day, per week, per month etc., as well as of the entire system. Can do year-to-year comparisons. Notifies when there is a problem. Perhaps you can talk to your installation company and find out about software monitoring of the output, as well as identifying any problems.

[cadreamer2015]

Was 2021 a great year for solar energy?

We added solar panels on 3/1/2021 so I don't have a full year for comparison. For March-December 2022 was up about 3% from 2021. For those 10 months 2023 was down about 8% from 2022. Most of the negative delta was in the first 5 months of the year 2023 (probably because of rain/clouds).

[cerequio]

They were on the house when we bought it in 2020. I think they were probably about 3 years old at that time.

If I could just find some kind of historical weather information on cloud cover or available sunlight for my area then I could graph that out and see if there is a correlation to the solar generation of each month/year.

Could they need a cleaning?

Sorry to piggy back on this thread but I had to ask - are we supposed to get solar panels cleaned? We have never had ours cleaned and they are 8 years old. No noticeable drop in production over time either.

[exodusNH]

They were on the house when we bought it in 2020. I think they were probably about 3 years old at that time.

If I could just find some kind of historical weather information on cloud cover or available sunlight for my area then I could graph that out and see if there is a correlation to the solar generation of each month/year.

Could they need a cleaning?

Sorry to piggy back on this thread but I had to ask - are we supposed to get solar panels cleaned? We have never had ours cleaned and they are 8 years old. No noticeable drop in production over time either.

It depends how dusty / pollen-y they get and how much rain. They are pretty slick, but depending on the nature of the contamination, you may need them cleaned.

[curmudgeon]

Last year had substantially more cloudy days here in N Cal. We definitely had reduced solar production both in the winter and spring. It's good to be aware of tree growth or any other factors that can cause shading to increase over time. Our solar install came with a little monitoring device that can collect date from the inverters and upload it to the web. I never bothered to set up continuous data collection, but I do fire it up every year or two to see what's happening in real time.

A simple and easy check that I do every few months is to pull up my utility account and drill down into the hourly data for a sunny day when nothing much electrical is running in the house. That lets me see my max power going to the grid at peak generation time, which should be consistent year to year. If that is lower that it should be, it would give me the clue to go looking for a failed panel or inverter.

[mjg]

Our solar panels generated ~8% less in 2023 than in 2022. Early 2023 was very wet - we finally broke the drought. I’m in San Diego county.

Yes, I remember that. I am in Temecula. Was 2021 a great year for solar energy?

Also - I'm seeing a severe degradation in generation during July and August. I know some of that is supposed to be due to heat causing poorer solar performance, but is there something with how Southern California Edison accepts energy credits that reduces the amount? Some kind of cap?

I'm basically due south of Temecula. I also had 8% less generation in 2023 than 2022. I track my generation and consumption in a spreadsheet with daily data. Weather varies. The best way to figure out if you system is degrading is to compare the max production in a given period -- ie the peak day in a given month. If the peak production for a single day for the period comparing this year vs last year is within a few percent, then it's unlikely you have a degradation issue.

As to cleaning, our biggest issue is dust. Never pay someone to clean - you will never earn back the cost. You might see 2% to 5% for fouling. If it's been a loooooong time between rain, you can use a hose to spray off your panels - but do not use a pressure washer. The rains we got in the last several weeks (and now) are doing an excellent cleaning.

[Tigermoose]

I think my reduction in net generation is due to increased electricity use. I didn't previously understand that your home will use electricity generated by your solar panels and then any excess will be sent to the electrical grid (SCE). I had thought that you just send your solar powered electricity directly to the grid, and then you just pulled the power you need. I did not understand that you actually use some of that solar power you are generating before sending any excess back to the grid.

So the reason my summer month net generation showed so low on my SCE statements is that I was using a ton of it and only had a small amount to send back to the grid.

I think we are using a lot more energy now than we did in 2021. Next step is to figure out why.

[corduroysuit]

It sounds like you have narrowed it down to the usage, but I'll add that I've seen drastic drops in production during years where we had wildfires in the region. It reduces your PV production during what should be the peak months (longer, sunnier days).

Editing to Add: Here's a site where you can compare weather history, including cloud cover. Might be worth comparing temperatures too, since higher summer temps could mean that you are running the A/C more than before.

https://weatherspark.com/h/y/1903/2023/ ... emperature

[gwanghoops]

Our solar panels generated ~8% less in 2023 than in 2022. Early 2023 was very wet - we finally broke the drought. I’m in San Diego county.

2023 was definitely a down year, here's my #s for a 2019 install in N. San Diego County and my 2023 is close to 8% down

2020 12197 kwh
2021 12472 kwh
2022 12279 kwh
2023 11458 kwh

[snackdog]

There are monitoring sites that you can use to answer your questions. One is SolarEdge, the one we use. It shows the output of each panel, per day, per week, per month etc., as well as of the entire system. Can do year-to-year comparisons. Notifies when there is a problem. Perhaps you can talk to your installation company and find out about software monitoring of the output, as well as identifying any problems.

SolarEdge can also show you the data from many nearby solar installations that should have the broadly same sun conditions as yours so you can compare.

https://monitoringpublic.solaredge.com/ ... cale=en_US

Here is our solar output by month in 2023 compared to a SolarEdge public site at a winery 12 miles away. The winery has about twice the installed capacity, so I scaled them back by half. Differences may be due to panel orientation, shading. We had an outage in August when an inverter died.

[Cobbles&Cols]

As others have noted, comparison of total solar output on specific clear-sky/peak production days during similar times of the year is a reasonable starting point for benchmarking.

If you really want to get into the weeds, you could download historical satellite-derived solar radiation data from NREL (https://nsrdb.nrel.gov/data-viewer). They currently have hourly data through 2022 available. For a quick first-order approximation, the annual sum of Global Horizontal Irradiance ("GHI") tells you how sunny (or not) a particular year was.

[WhyNotUs]

So the reason my summer month net generation showed so low on my SCE statements is that I was using a ton of it and only had a small amount to send back to the grid.

I think we are using a lot more energy now than we did in 2021. Next step is to figure out why.

Did you add air conditioning or electric vehicle, they are most likely big ticket users.

Kill a Watt meters are fun to check things that plug in. They cost about $30 and your electric utility may have them to loan.

[Point]

If you don’t have the ability to monitor your production and consumption vs what you send to the grid, you can look at the product from sense.com and see if their solar monitoring product will give you better insight.

Yiu probably have the ability to view your individual panel production to determine if a panel is not performing well. Also, eliminate any question of shading- ie trees growing into the panel view and blocking part of the day.

[mkc]

[Topic is now in Personal Consumer Issues - mod mkc]

[yankees60]

Were they new in 2021?

Most panels have a an output loss of 2-3%/ year for the first few years until they plateau. Also most solar installers have a generation warranty /guarantee. It might be good to review the install documents.

My system has monitoring at the panel level that I can see the output over a day/week/month/year/ all time.

My understanding was that it was on the order of 0.5% per year?

[lazydavid]

My understanding was that it was on the order of 0.5% per year?

The panels I’m awaiting installation on are guaranteed to be at 92% or better at the end of the 25-year warranty period. That is broken down as a degradation of no more than 2% in the first year, and no more than 0.25%/year in years 2 through 25.

[yankees60]

Do you not have some way of monitoring performance? I'm in the process of investigating solar and that is one of my questions to all of them? How am I going to be able to monitor performance.

[jm1495]

With string inverters there are monitoring options per panel.

[yankees60]

With string inverters there are monitoring options per panel.

That is true? That does not describe the microinverters, which seems to logically follow?

[lazydavid]

With string inverters there are monitoring options per panel.

That is true? That does not describe the microinverters, which seems to logically follow?

Microinverters are one per panel, so by definition any monitoring solution that reads data from microinverters can give you performance data about individual panels.

[cmr79]

I have IQ8 microinverters. I can see my exact production in kWh per panel for every individual day my system has been installed as a feature of the microinverters themselves.

With a string inverter, because it is centralized, it doesn't know how individual panels are producing...it has to aggregate and balance everything. Power optimizers can be added to a string inverter system to do this (if attached to each individual panel, much like a microinverter), and there are other specific monitoring systems that can be added, but none of them are strictly required as part of a string inverter. Because there are so many ways of doing this, though, monitoring per panel production probably shouldn't sway someone from one inverter method to another.

[yankees60]

I have IQ8 microinverters. I can see my exact production in kWh per panel for every individual day my system has been installed as a feature of the microinverters themselves.

With a string inverter, because it is centralized, it doesn't know how individual panels are producing...it has to aggregate and balance everything. Power optimizers can be added to a string inverter system to do this (if attached to each individual panel, much like a microinverter), and there are other specific monitoring systems that can be added, but none of them are strictly required as part of a string inverter. Because there are so many ways of doing this, though, monitoring per panel production probably shouldn't sway someone from one inverter method to another.

So, was this a correct or incorrect assertion?

"jm1495 wrote: ↑Tue Oct 01, 2024 11:12 am
With string inverters there are monitoring options per panel."

[Coastingthrulife]

Tiger,

I had solar panels installed in 2017 and, because I like it, I track daily weather (amount of sun, ow and high temp), production, usage in a spread sheet. I do it for a couple of reasons - to see how to limit our consumption and to see if the panels are producing like they are designed to do. Our system is rated at 4,550 watts (14 panels @ 325 watts each) on two strings (this was before microinverters).

Specific comments:
- Our panels carry a 20 guarantee of at least 95%
- I wash the panels 3-4x each year (pollen and dust) with a soft bristle brush on a long pole. This can make as much as 5% difference.
- I monitor instantaneous generation and compare to the theoretical 4,550 watt capacity. You can do this by checking the system's inverter at the display screen. My panels face due south with no obstructions.

To date, we have seen 0% degradation across the system. I know this because our max daily production is as high this year as the first year and our instantaneous production has not declined either.

I suggest you track daily production, how much goes to the grid, and net usage every day for a month. Get the readings at the same time each day. This will tell you which days are high usage. For us, it is laundry day. And, as it is getting darker sooner, our lights are on more and drawing power. A/C is our biggest single consumption source. The winter months see higher usage as the furnace blower runs more and x-mas lights add usage for December. You would be surprised how much the stove/oven use if you use those appliances alot.

[TomatoTomahto]

I have IQ8 microinverters. I can see my exact production in kWh per panel for every individual day my system has been installed as a feature of the microinverters themselves.

With a string inverter, because it is centralized, it doesn't know how individual panels are producing...it has to aggregate and balance everything. Power optimizers can be added to a string inverter system to do this (if attached to each individual panel, much like a microinverter), and there are other specific monitoring systems that can be added, but none of them are strictly required as part of a string inverter. Because there are so many ways of doing this, though, monitoring per panel production probably shouldn't sway someone from one inverter method to another.

Yes. I have both string and micro inverters. Both report per panel.

[yankees60]

I have IQ8 microinverters. I can see my exact production in kWh per panel for every individual day my system has been installed as a feature of the microinverters themselves.

With a string inverter, because it is centralized, it doesn't know how individual panels are producing...it has to aggregate and balance everything. Power optimizers can be added to a string inverter system to do this (if attached to each individual panel, much like a microinverter), and there are other specific monitoring systems that can be added, but none of them are strictly required as part of a string inverter. Because there are so many ways of doing this, though, monitoring per panel production probably shouldn't sway someone from one inverter method to another.

Yes. I have both string and micro inverters. Both report per panel.

Are there power optimizers on your micro inverters?

[TomatoTomahto]

I have IQ8 microinverters. I can see my exact production in kWh per panel for every individual day my system has been installed as a feature of the microinverters themselves.

With a string inverter, because it is centralized, it doesn't know how individual panels are producing...it has to aggregate and balance everything. Power optimizers can be added to a string inverter system to do this (if attached to each individual panel, much like a microinverter), and there are other specific monitoring systems that can be added, but none of them are strictly required as part of a string inverter. Because there are so many ways of doing this, though, monitoring per panel production probably shouldn't sway someone from one inverter method to another.

Yes. I have both string and micro inverters. Both report per panel.

Are there power optimizers on your micro inverters?

They were installed before I bought the house, but I think so.