Question about SolarEdge inverter sizing and clipping

[Ampster]

Thanks for the update. Multiple azimuths illustrate how different ratios work for different situations. Keep us informed as you progress through the soltice.

[Snipely]

This has been a very instructive thread and I appreciate everyone's contribution that helped my understanding. I recently expanded to a 7000W array with an SE5000A-US inverter (no worries on the DC side, as I have multiple azimuths) The specs say this inverter should clip at 5400, and I'm seeing around 5200 W. (Still unsure if this is a real number - is it?) I looked at my last few years of data and I found that I generally peak in April and May at ~4.35 kW, which was with a 5.5 kW system, and on occasion only. Doing the math, the new peak should be about 5.5 kW. I've seen some of the calculations here and fairly confident I am not losing much production overall. Even though my setup is not typical, I hope this adds some useful data to the clipping discussion.

[ButchDeal]

Why would a line side tap be more expensive? If anything it is cheaper because you don't have to buy a circuit breaker.

thats funny
there are special taps required that cost money, often a box or trough that costs money, fused disconnect (or breakers), more electrician time...

[macaddict]

or switching from using main panel to doing lineside tap ($1k?)

Why would a line side tap be more expensive? If anything it is cheaper because you don't have to buy a circuit breaker.

[macaddict]

Thanks for the reply. I do not think I will use the EV charger as the inverter is mounted outside my house to the electric meter box far from my garage. My electric provider does 1 to 1 metering too so I do not think I will need a solar EV charger since I can use the electric grid provider as my "backup battery". I'll have to have a circuit run to the garage from my internal panel, though, for a future electric car...if I go that route in a year or two.

I am not familiar with PVWatts. I know that JPMs output seemed to show that there wasn't a major increase going from the 7600 W inverter to the 10,000 W inverter, it seemed. But, it does seem like there can be some increase there over the 7,600.

I still am not sure what to do. However, I've left a note with my installer asking if they could replace the 7,600 inverter with a 10,000 inverter. This may be an issue for them but I will see what they say.

Any other advice would be appreciated.

If you are not using the EV charger part and are already using a line side tap, I would replace the inverter with a larger one.

[J.P.M.]

I know that JPMs output seemed to show that there wasn't a major increase going from the 7600 W inverter to the 10,000 W inverter, it seemed. But, it does seem like there can be some increase there over the 7,600.

Yea, to the degree my misuse of PVWatts makes any sense, something like about 0.6 % increase in annual output for a 10 kW inverter over the 7.6. That was the purpose of the exercise.

[nwdiver]

Any other advice would be appreciated.

I have a 4.5kW array on a 3.8kW inverter in SE NM that I've seen clip <5 times in a year. Panels lose ~0.5%/C so on a warm day 4.5kW is really ~4KW and on a hot day ~3.5kW. You may not get much more output by upgrading to a 10kW inverter.

For Illinois PV Watts is estimating a 32kWh/yr increase from a 7.7kW inverter to 10kW inverter....

[Jeff72]

I didn't say that...

You ask if there was truth in the installers statements.

from what we are seeing and from JPMs calculations you are seeing pretty little clipping and you would lose the EV charger if you changed.
You can use PVWatts to calculate the production with a 1:1 inverter to DC ratio and see the difference as he has done

Thanks for the reply. I do not think I will use the EV charger as the inverter is mounted outside my house to the electric meter box far from my garage. My electric provider does 1 to 1 metering too so I do not think I will need a solar EV charger since I can use the electric grid provider as my "backup battery". I'll have to have a circuit run to the garage from my internal panel, though, for a future electric car...if I go that route in a year or two.

I am not familiar with PVWatts. I know that JPMs output seemed to show that there wasn't a major increase going from the 7600 W inverter to the 10,000 W inverter, it seemed. But, it does seem like there can be some increase there over the 7,600.

I still am not sure what to do. However, I've left a note with my installer asking if they could replace the 7,600 inverter with a 10,000 inverter. This may be an issue for them but I will see what they say.

Any other advice would be appreciated.

[Jeff72]

That is nonsense. Below is a graph typically used to justify clipping. This may have been true 15 years ago, but now with high efficiency inverters it is simply not true.

My installer put 11.25 kW on a SE7600 inverter and I clipped 4 to 5 hours almost every day from March until October. Below are two of my graphs from this year after my installer admitted that they were way too aggressive with the oversizing. My inverter would also overheat and did derate a few times as well. The day I got over 76 kWh is interesting. I peaked at 11.34 kW with a 11.25 kW system on three separate facing arrays. If I only had the SE7600 inverter for that day, I would have maybe produced 60 kWh.

Thanks. Yes, that is what I am thinking. I think my installers are going by old traditional methods of design and am now under the impression that I would mostly see benefits if I swap the inverter from 7,600 to 10,000 inverter.

[Jeff72]

Yes, I see that. Understood. I appreciate your predicament. But you asked what I'd do.

I'm aware I mouth off a lot. Folks accuse me of telling them how to build a watch if/when they ask me what time it is. In rereading my reply, I now realize that in an attempt at concise brevity, I gave an incomplete answer.

Bottom line for what I'd do: A lot of use reduction and conservation upfront and see what that does to my load. Then, a serious cost analysis as part of a preliminary design that addresses whether or not PV makes sense from a life cycle cost standpoint at all, including the effect that obstruction has on system cost effectiveness and also system design and overall project goals.

What I left out was that, for me only, after safe design, a major design goal among others including serviceability, is the lowest long term cost means of providing reliable power to a residence by using the most cost effective mix of use reduction, conservation measures, grid power and PV - and probably in that loose order. So, and again since you ask, I'd do it differently than you appear to have done it.

To your question, if I had your situation, after setting goals and doing the other, more cost effective stuff first, I'd first spend some time estimating the effect on system design and complexity, and the effect on the cost effectiveness of the system of a big obstruction in just about the worst possible location relative to the array as well as what complications and other impacts that obstruction would have on the rest of the design.

If it was my situation, since one of my goals is the least long term cost of providing electricity rather than PV as the first and maybe only line of defense against high and mostly self inflicted electric bills, I might still do PV. But if I did, I wouldn't be surprised to find out the best system for my money would be smaller. It would probably, and reluctantly (because of what I see as more complexity and more failure points from that added complexity), include optimizers because life is not perfect and is usually a set of compromises. But in this case, if I was doing it that way, if I did PV at all - which is not a slam dunk BTW - I'd consult with someone like Butch who, even though we probably disagree on their worth and efficacy, knows more about optimizer systems than I do.

Take what you want of the above. Scrap the rest.

Thanks, I appreciate your info. I have done many things already like use LED bulbs in the house and add insulation in the attic and spray foam around the box area in the basement and such. Solar has always been an interest of mine so I finally made the decision. I wanted to maximize my south facing two roofs solar generation for current house usage plus a possible future electric car or even two eventually. I feel that we did what we could with the roof and the 27 LG 365 panels in an arrangement that could do the best we can with what we had. I just feel limited now by the inverter. I originally though the 7600 would oversupply on the AC side, but that is not the case. I feel that I should get closer to the DC side 9855 W generation I would think if I get a 10,000 W inverter instead of the 7,600 W inverter and maximize the solar generation I can get.

[discodanman45]

So, if I had to do it again, go with 10k inverter? Is there any benefit to 7600 inverter besides price?

Installer claimed 7600 inverter would begin generating earlier in day and generate later in day versus 10k inverter...does that sound right? he said due to voltage needed to start generating being less on 7600 inverter.

That is nonsense. Below is a graph typically used to justify clipping. This may have been true 15 years ago, but now with high efficiency inverters it is simply not true.

My installer put 11.25 kW on a SE7600 inverter and I clipped 4 to 5 hours almost every day from March until October. Below are two of my graphs from this year after my installer admitted that they were way too aggressive with the oversizing. My inverter would also overheat and did derate a few times as well. The day I got over 76 kWh is interesting. I peaked at 11.34 kW with a 11.25 kW system on three separate facing arrays. If I only had the SE7600 inverter for that day, I would have maybe produced 60 kWh.

[J.P.M.]

I do have that chimney so I kind of need the Optimizers. I was originally going for microinverters but chose the Optimizer route for a variety of reasons.

Yes, I see that. Understood. I appreciate your predicament. But you asked what I'd do.

I'm aware I mouth off a lot. Folks accuse me of telling them how to build a watch if/when they ask me what time it is. In rereading my reply, I now realize that in an attempt at concise brevity, I gave an incomplete answer.

Bottom line for what I'd do: A lot of use reduction and conservation upfront and see what that does to my load. Then, a serious cost analysis as part of a preliminary design that addresses whether or not PV makes sense from a life cycle cost standpoint at all, including the effect that obstruction has on system cost effectiveness and also system design and overall project goals.

What I left out was that, for me only, after safe design, a major design goal among others including serviceability, is the lowest long term cost means of providing reliable power to a residence by using the most cost effective mix of use reduction, conservation measures, grid power and PV - and probably in that loose order. So, and again since you ask, I'd do it differently than you appear to have done it.

To your question, if I had your situation, after setting goals and doing the other, more cost effective stuff first, I'd first spend some time estimating the effect on system design and complexity, and the effect on the cost effectiveness of the system of a big obstruction in just about the worst possible location relative to the array as well as what complications and other impacts that obstruction would have on the rest of the design.

If it was my situation, since one of my goals is the least long term cost of providing electricity rather than PV as the first and maybe only line of defense against high and mostly self inflicted electric bills, I might still do PV. But if I did, I wouldn't be surprised to find out the best system for my money would be smaller. It would probably, and reluctantly (because of what I see as more complexity and more failure points from that added complexity), include optimizers because life is not perfect and is usually a set of compromises. But in this case, if I was doing it that way, if I did PV at all - which is not a slam dunk BTW - I'd consult with someone like Butch who, even though we probably disagree on their worth and efficacy, knows more about optimizer systems than I do.

Take what you want of the above. Scrap the rest.

[ButchDeal]

OK, on that note, and correct me if i'm wrong here, in my case with the 9,855 kW panel array, it will be worthwhile to gain the clipping loses and to go to a 10k inverter, right?

So now i'm back on the plan to asking the installer for a 10k inverter replacement. Since I have a line side tap, should the existing wiring for the 7600 inverter work for the 10k inverter? I'm not sure what gauge wire they used but I am wondering if the gauge required for 7600 inverter will work for 10k inverter also?

I didn't say that...

You ask if there was truth in the installers statements.

from what we are seeing and from JPMs calculations you are seeing pretty little clipping and you would lose the EV charger if you changed.
You can use PVWatts to calculate the production with a 1:1 inverter to DC ratio and see the difference as he has done

[Jeff72]

Since you're asking, my preference, for single orientation arrays, and until I found out differently, would be to mimimize shading on the array, And KISS as a time tested (for me anyway) method to help avoid problems, and skip the more parts to fail optimizer design, and size a string inverter ~ = (STC rating of the array) * (inverter efficiency).

However, in the quest to find out differently, and keeping in mind that none of us is as smart as all of us, I'd consult with folks like Butch because he knows more about SolarEdge than I know about them and their products, and he might convince me that all the problems I seem to read about popping up around here in inordinate quantities about SolarEdge quirks, problems and crappy customer service are simply due to ignorant users.

Otherwise, see Butch's comments about the rest of your post.

I do have that chimney so I kind of need the Optimizers. I was originally going for microinverters but chose the Optimizer route for a variety of reasons.

[Jeff72]

Nope no truth at all.
Voltage is irrelevant as the optimizers will boost the voltage anyway, however both inverters have the SAME operating voltage.
the 10000kw inverter is ever so slightly less efficient but way less so than cliping losses
the 7600 has optional EV charger and usually doesn't require a line-side tap
10000kw usually does require a lineside tap...

line side tap being a slight added cost.

OK, on that note, and correct me if i'm wrong here, in my case with the 9,855 kW panel array, it will be worthwhile to gain the clipping loses and to go to a 10k inverter, right?

So now i'm back on the plan to asking the installer for a 10k inverter replacement. Since I have a line side tap, should the existing wiring for the 7600 inverter work for the 10k inverter? I'm not sure what gauge wire they used but I am wondering if the gauge required for 7600 inverter will work for 10k inverter also?