Any smart guys here able to estimate what I'm loosing with Clipping

[J.P.M.]

My panels are 300 watts each I have 34 of them.

Thank you.

[J.P.M.]

Dan: Thank you for the article. That is an excellent read, and clearly shows that an optimum system has some clipping.

In very broad terms, optimization is deciding how much to spend on panels & racking versus how much to spend on inverters. Is it a better investment to buy one more panel and one more small microinverter, or to buy larger microinverters?

Curiously, this is a moving target. Panel cost will drop with time, racking cost will go up with time, installation cost will go up with time, and inverter costs will go down with time. My crystal ball suggests that the optimum point will go towards larger inverters and less clipping in the future, but time will tell.

Optimization is about a lot more than cost. It is a process of balancing design goals and priorities using available resources, including financial resources to obtain the most fit for purpose outcome in the safest way possible. An optimum system is one that best meets the duty it's designed for. The best match between inverters and panels is a better design parameter than simple overpaneling that will give a better design, and if done correctly, minimize if not eliminate clipping. Such systems may or may not have clipping. Clipping is not a design goal in a fit for purpose system. Some clipping may need to be tolerated in a balance of design requirements, but it's not a goal, any more than designing a vehicle around a governor that limits engine output.

[Ampster]

Optimization is about a lot more than cost. It is a process of balancing design goals and priorities using available resources, including financial resources to obtain the most fit for purpose outcome in the safest way possible. An optimum system is one that best meets the duty it's designed for. ....

It all depends on how one wants to define "fit for purpose". If it means utility to the user it could be subjective, like the above responses to the OPs question. I have seen definitions of "fit for purpose" as, meeting the customer's needs.
We have not heard back from the OP if the installation is meeting his needs? It might take a year of data collection to precisely answer his question about how much he is losing to clipping. It will vary by weather. As the panels degrade it may decline over time but the system output may not decline as the clipping declines. To some that may be a optimum outcome.

[J.P.M.]

It all depends on how one wants to define "fit for purpose". If it means utility to the user it could be subjective, like the above responses to the OPs question. I have seen definitions of "fit for purpose" as, meeting the customer's needs.
We have not heard back from the OP if the installation is meeting his needs? It might take a year of data collection to precisely answer his question about how much he is losing to clipping. It will vary by weather. As the panels degrade it may decline over time but the system output may not decline as the clipping declines. To some that may be a optimum outcome.

Precisely. But the term "fit for purpose" (and not the legal term "fit for particular purpose" which has a particular meaning and is not precisely the same) has the usual meaning as I undersatnd it means a product or service is adequate for the duty or service for which the end user intended. Within some guidelines, the term fit for purpose is always a moving target - and I'd suggest its particular definition is mostly within the purview of and highly dependent on the goals of whoever is paying for the system, but it seems fairly obvious, to me anyway, that there's more to it than cost alone.

My comments were a response to Bob-n's seeming idea that fit for purpose is a concept that has only one criteria - lowest cost.
It ain't.

It's about a balance of priorities, goals and the compromises - including but not exclusively financial - made to meet and achieve those priorities and goals, one of which is cost.

[Skiman26]

I wish I could find out how much more juice above 8.4kwh my system would provide if I had larger inverters it seems like it would go quite a bit higher because it’s clipping for 3 hrs 30 minutes every day. Would it be normal for a 10.2kwh system to do that. That’s what I am curious of? Or would a person typicall install a larger inverter than an IQ7 for a 10.2kwh system?

[bob-n]

Skiman26,

Yes you can find out. To find out, go through the process previously mentioned (thank you J.P.M.), using PVWatts to model your system over a 1 year period with the two different inverters. Yes, it's a bit of work. For many of us, it's a worthwhile learning experience.

You ask if your system is "normal". There is no normal. Each system is a design based on what's available and how much money is being spent. As you know, there is nothing between the iQ7 and iQ7+. The designer had to pick one. They could have picked the iQ7+ and the system would have cost more and produced more. They also could have used more expensive or cheaper panels, used fewer or more panels, etc. There is no right answer.

If you want to know for certain whether it is a good investment to upgrade your inverters, you need to go through the model as described in the previous message from JPM, then go through the simple analysis of estimating the cost to upgrade, based on material and labor for your specific system (see my rough estimate).

If you're not interested in doing all of that work and you want someone to tell you, here's the answer. It's not worth the investment.

I welcome anyone to prove me wrong.

[Skiman26]

I appreciate your advise, thank you. There a part of me that’s frustrated with the design of this system it’s just hard to make sense of building something from scratch and not having it perform to its fullest potential.

[solardreamer]

Did you tell your installer that you wanted a system that doesn't clip ever? Otherwise, he followed standard practice.

[oregon_phil]

I appreciate your advise, thank you. There a part of me that’s frustrated with the design of this system it’s just hard to make sense of building something from scratch and not having it perform to its fullest potential.

FWIW, also realize that your new system has super clean panels from the factory and are probably putting out maximum watts being spring time. In the first year, in the spring, my panels were often putting out Pmax on cold clear sunny days. Now that farm dirt, bird droppings and environmental dust has settled on the panels, they have mellowed out. In other words, less energy is getting to the solar cells.

[J.P.M.]

I appreciate your advise, thank you. There a part of me that’s frustrated with the design of this system it’s just hard to make sense of building something from scratch and not having it perform to its fullest potential.

Well, FWIW, that's what you get when inverters are not large enough to handle everything they're being fed from the array(s). It takes a bit of analysis to see if increasing the inverter'(s') size makes economic sense. If the amount of clipping is small, I'd agree with what Bob-n writes - it probably doesn't.

[Ampster]

I appreciate your advise, thank you. There a part of me that’s frustrated with the design of this system.......

Your DC to AC ratio is not that agressive at 1.25 to 1. What other aspect of system design are you referring to? As others have said your system seems to be putting out a lot of kWhs.
I have a system that is 1.5 to 1 and I see clipping also. I did the math when i first saw the clipping and I am not losing much . Do that comparision, as suggested by others . Until you do the math and get objective numbers, your imagination about the area under that hypothetical curve will continue to bug you.
Focus on the power that you are producing not on the power that you think you could produce on a perfect day. Also on hotter days the panels output could taper off. I see less clipping on hot summer days than I did in the cooler days of Spring. The good news is that as the panels get dirty and old, the clipping will be less and your inverters will still be going full blast and you will be getting the same kwhs as you are today.

[theoak]

Skiman26,

Yes you can find out. To find out, go through the process previously mentioned (thank you J.P.M.), using PVWatts to model your system over a 1 year period with the two different inverters. Yes, it's a bit of work. For many of us, it's a worthwhile learning experience.

You ask if your system is "normal". There is no normal. Each system is a design based on what's available and how much money is being spent. As you know, there is nothing between the iQ7 and iQ7+. The designer had to pick one. They could have picked the iQ7+ and the system would have cost more and produced more. They also could have used more expensive or cheaper panels, used fewer or more panels, etc. There is no right answer.

If you want to know for certain whether it is a good investment to upgrade your inverters, you need to go through the model as described in the previous message from JPM, then go through the simple analysis of estimating the cost to upgrade, based on material and labor for your specific system (see my rough estimate).

If you're not interested in doing all of that work and you want someone to tell you, here's the answer. It's not worth the investment.

I welcome anyone to prove me wrong.

I went through the PVWatts process. My installer wanted a 1.36 ratio. The next inverter size up gave me a 1.03 ratio; hence, almost 1:1. Via PVWatts though with the 1:1 inverter gave me about 5% more yearly output. If I lose 1% per year I felt that was like losing 5 years right off the bat if I went with the 1.36 inverter. PVWatts also said that I had a 90% likelihood to get 95% output and a 10% chance to get 102% output. I interpreted that as for my area my panels would be running at peak for a good chunk of time and hence having a lower ratio would be in my best interest which is also what their analysis results concluded when I plugged in both ratios. It was no extra cost, so I went with the 1:1 based system. I still clip.

[J.P.M.]

I went through the PVWatts process. My installer wanted a 1.36 ratio. The next inverter size up gave me a 1.03 ratio; hence, almost 1:1. Via PVWatts though with the 1:1 inverter gave me about 5% more yearly output. If I lose 1% per year I felt that was like losing 5 years right off the bat if I went with the 1.36 inverter. PVWatts also said that I had a 90% likelihood to get 95% output and a 10% chance to get 102% output. I interpreted that as for my area my panels would be running at peak for a good chunk of time and hence having a lower ratio would be in my best interest which is also what their analysis results concluded when I plugged in both ratios. It was no extra cost, so I went with the 1:1 based system. I still clip.

If cost effectiveness and things like life cycle costing weren't in play, good design might well point to a DC/AC ratio of closer to 1.00 or maybe a few % higher to handle any panel overspec tolerance.

But since cost effectiveness is usually a big, if not the biggest reason for residential PV's existence and because inverter incremental watts cost less than panel incremental STC watts, it's usually more cost effective to size the array to meet the annual load fraction desired (which may be <100 % load fraction), then initially size the inverter(s) to meet the maximum modeled 1 hour clear sky array generation for that array size, and then iterate the inverter size downward until the clipping affects the lifecycle cost effectiveness of the whole system or until clipping becomes noticeable and/or problematic or a concern.