To oversize SolarEdge Inverter OR NOT?

[posol]

Hello,
I am installing 11 x LG315 panels and considering either SolarEdge 3800 or 5000 ones. 3800 will be more than enough for my current systems, but I may want to add some additional panels later on (cannot afford them right now). So for just 70$ extra I can get SolarEdge 5000 which is a no-brainer financial wise. BUT, it is too good to be true and perhaps there is something that I am missing in this equation ... So is there any downside to this over-sizing?

Thanks for the help

[thejq]

Hello,
I am installing 11 x LG315 panels and considering either SolarEdge 3800 or 5000 ones. 3800 will be more than enough for my current systems, but I may want to add some additional panels later on (cannot afford them right now). So for just 70$ extra I can get SolarEdge 5000 which is a no-brainer financial wise. BUT, it is too good to be true and perhaps there is something that I am missing in this equation ... So is there any downside to this over-sizing?

Thanks for the help

Sure $70 is a no brainer IMO if you think it will get you more freedom later on. But to add more panels later, it might not be as straight forward. Most likely you have to get the original installer to do it to keep the warranty intact. Also SDGE NEM agreement only allow you to increase the system size by up to 10%, or 1 panel in your case, without reapplying. And the permit also needs to be amended. So unless you are adding a lot of panels at once, the additional cost may make it not economically worthwhile.

[posol]

Thanks. But any technical reason that it is a bad idea and will degrade my current system efficiency?

[schmoot]

Why not the 6K inverter? It's only like $30 more than the 5K inverter.

[foo1bar]

And the permit also needs to be amended.

I would expect it to be a brand new permit. I don't think normally you amend a permit that has had it's final inspection.
The permit may be pretty cheap. I'd guess for me it might be $50 (the minimum permit cost) - but at most it'd be the same ~$300 I paid for the full project.

I don't know what it takes to deal with SDGE and get a new NEM - so can't comment on the cost of that.

I think if adding new panels did something that caused problems (ex. broke a optimzer plug) there would be problems getting a claim on a warranty claim. But I don't think that would affect my decision much.

[FFE]

A few things. Do you know what size your main panel breaker is? Do you have three phase or two phase coming from the power company?

Keep in mind that the 3800 is rated up to 5100 watts STC and that the LG315 are PTC rated at 287.4 watts. You will only get above 300 watts from each panel under ideal conditions. Like cool day with lots of clouds to reflect unobstructed direct sun close to solar noon. So, the 3800 should be good up to 13 panels without clipping and rated for up to 16 panels.

[ndabunka]

Everyone replying is missing the ACTUAL question

The OP is asking if there is a TECHNICAL reason not to go with the larger inverter. He's not asking if there are REGULATORY considerations (which is what it seems like others on here have defaulted to). LIke him I have heard others saying that using too large a inverter COULD be problematic. I believe it has something to do with the fact that the inverter "requires" a certain amount of voltage/watts/power to come through it in order for it to function correctly.

I have heard some say that the inverter might not work AT ALL if it is significantly oversized. Is that true? If so, what is the math behind it. How large of an inverter COULD be used on a system the size he has specified and it still function as designed?

[solarix]

Do the 5kW inverter. That is a very typical size for most homes and someone down the road will be thankful they can up the array size without hassle. Going beyond 5kW means upping the wiring to the next size (8ga instead of 10ga, and 60A disconnect instead of 30A etc) so involves additional expense. 5kW is definitely the "sweet spot" in cost effectiveness. SolarEdge systems are very flexible and adding more panels later on will be easy. Your building dept will no doubt want another donation to approve adding on more panels, but if the inverter is not changing then whose to know?

[sensij]

Along the lines of some other recent posts, here are the breaker requirements:

3800 W - 20 A
5000 W - 40 A
6000 W - 40 A
7600 W - 40 A

If you have 100 A electrical panel, stay with 3800.
If you have 200 A panel, any are fine.
If you have 125 A panel, you may need to drop the main breaker down to 100 A, then any are fine.

[solarix]

5000W inverter is 30A breaker. 5000/240 *1.25 =26A
6000W inverter can be 35A breaker (probably a special order) 6000/240*1.25 = 31A

[FFE]

The OP is asking if there is a TECHNICAL reason not to go with the larger inverter.

The OP asked if there is any downside. So, if it is a 100 Amp panel and the OP installs a 16A breaker, installs the 5000, adds more panels and gets a super sunny day it might trip the breaker. Seems like a downside.

What are the efficiency curves? What is the efficiency at 2000-3000 watts for both inverters. Probably the same. However if there is a greater loss for one than the other...

And it is three pounds heavier.

[foo1bar]

The OP is asking if there is a TECHNICAL reason not to go with the larger inverter. He's not asking if there are REGULATORY considerations (which is what it seems like others on here have defaulted to).

Actually we were discussing ECONOMIC considerations - not regulatory. (or at least I was)

I haven't seen a solaredge efficiency curve for any of their inverters. So really I don't know whether you would gain or lose a little efficiency by running 2kW through their 3800W inverter vs. their 5000W inverter. I have seen curves for Sunnyboy - and on those I think it's pretty flat until you get down below 10% of the rated power. So my best guess is that the effect of upsizing is largely going to be unnoticed in overall power production. That it'll be within 1-2% overall (and that could be either better or worse, since at least some of the graphs have higher efficiency at ~20% than they do when running at 50% or 100%). Quite possibly keeping a nearby tree pruned will make more difference.

[posol]

Thank you all for the insight.

My Panel is 200A, so I am fine with either. However, I have heard that there is "startup voltage" for some of the inverters and if I go very oversize then the number of the panels may not be enough to reach the starting operation for a big inverter when the light is low (early morning or late afternoon). But I cannot find such information for SolarEdge inverters nor their operating range graphs.

Any thought of these?

[foo1bar]

So, if it is a 100 Amp panel and the OP installs a 16A breaker, installs the 5000, .

There are no 16A breakers.
But lets assume you meant 20A. (16 * 1.25)
Installing a 5000W inverter with a 20A breaker is not up to code.
Therefore it would not be installed that way.
If it was installed it correctly, it'd be a 30A breaker, with appropriate wire size for 30A. With a correct installation the breaker would not trip even if the inverter reached it's peak output.

[FFE]

Thank you all for the insight.

My Panel is 200A, so I am fine with either. However, I have heard that there is "startup voltage" for some of the inverters and if I go very oversize then the number of the panels may not be enough to reach the starting operation for a big inverter when the light is low (early morning or late afternoon). But I cannot find such information for SolarEdge inverters nor their operating range graphs.

Any thought of these?

Some inverters have adjustable startup voltage.

Oops 20 Amp breaker that trips is what I should have typed. Also, I looked it up the 5000 can be set to limit power anyway, so if you didn't follow code you could limit power.