Is this the Right Inverter for the job?? (Seems underpowered 14.5kW System)

[adam61]

I've had great luck with my installer's knowledge, but this didn't quite add up so I wanted the proverbial second opinion. My system will have 38x390w LG N2W Panels producing 14.43kW. The original project was only about 12.4kW, but I had some higher usage needs while we were waiting on approval so we made the adjustment. It also has 38 P400 Power Optimizers.

Where I'm confused is the original system was only about 1kW above the Solar Edge 11.4kW (SE11400H) rating, and I was told since with 90% AC conversion I would only have a max theoretical of 11.2kW and it should work just find since they can handle a bit extra.

Since I've upped the system size I asked again as I'm at 14.43kW DC and 13kW or so max AC. The converter no longer appears large enough. The answer I got was that was SolarEdge's largest consumer model (that appears accurate) and 2 inverters will cause further losses from the additional connections. Does this sound correct? My panels are in such a way they all face the same way and get sun at the same time creating a huge spike during probably 4-6 hours of the day and much less other times. I'm feeling like I'm wasting money if I have quite a bit of trim during the hottest part of the day, Especially, since all the panels get or don't get sun at exactly the same time.

Please help!! Trying to finalize documents today and I've done a lot of research, but this is one area that was a little too specific to ask and probe with the right questions.

[ButchDeal]

Well they have a few problems.
First the P400 is the wrong optimizer for the LG390N2W which has an Isc of 10.39 but the P400 has a max Isc rating of 10.1. They should be using the P505

not sure where they get 90% AC conversion figure from...
Two inverters do NOT cause any more losses than a single inverter.

With your PV modules all in the same plane you will definitely have clipping.
Do you have shadows? maybe a photo of the layout.


Yes the SE11400H is rated to allow upto 17.65kW DC on the input side but it will not inverter any more than 11.4kW. SolarEdge does not make recomendations on inverters on their site, they just tell installers if something is allowed.

You best install would be two SE7600H inverters but should definitely have the P505 optimizer not P400

[adam61]

So both are an issue? Is the 10.1 vs 10.4 a big issue on the optimizers, they say that's all they love ever used on those panels? I'm no electrician. They agreed I'd get trim but that the 11.4 was rated for 155% so it would be a loss of production at the best part of the day not a overload issue. They are looking into 2 smaller ones but reiterated there would be 3-5% loss, potentially harder to monitor and a small price difference.

[JSchnee21]

Butch is definitely the expert on all things Solar Edge -- he won't steer you wrong. If your installer uses the wrong optimizer, even if the numbers are close, SE won't honor the warranty. SE optimizers and inverters are super efficient so I would be skeptical of the 3-5% loss the installer is claiming.

I have a 11.4kW SE inverter (older A-series) with 37 @ 330W panels (12.2kW) with the P400's. Although all of my panels face 175 degrees, my pitch (20 degrees) is sub-optimal for my latitude (NJ). I occasionally (maybe 5 or 10 times per year) reach full output (11.5-12kW) but never clip for more than a few minutes at a time.

While the newer HD's series "support" higher DC to AC ratios without voiding the warranty, that does not mean that higher ratios should be used -- in particular in your case with a single roof face. It sounds like your installer is not all they're cracked up to be.

But, it is true that 2x7600HD will cost more than 1x11,400HD both for the inverter and for the electrician to wire it. Not a lot more, perhaps $500-1500. Each inverter will have two strings -- one 9 panels and one 10 panels.

I assume you're getting a line side tap? Or you have a very large breaker panel -- 400amps (or 2x200)?

I strongly recommend the Solar Edge Consumption monitoring option. And be sure to use Ethernet for your uplink -- NOT cellular or Zigbee. The comms for the two inverters should be wired together via 485. I think only one Ethernet is required -- but I'm sure Butch will correct me if I am wrong.

When the Solar Edge Monitoring portal in configured correctly, it will be no more difficult to manage / understand what is going on than if you had only a single inverter.

[JSchnee21]

Comparing pricing at the AltE store for example.

One SE 11400HD is
$2,245.00

One SE 7600HD is
$1,579.00

So that's $913 more for 2x7600HD plus the addition parts the electrician will to wire them up.

The P400 is $69 each. While the P505 is $82.79 each. So that's $524.02 more for the optimizers.

Of course other distributors may be more or less.

How's your DC STC price per watt looking? It should be in the range of $2.75-$3.25 / W DC STC (before any discounts, incentives, or Federal rebate).

38 * 390W = 14,820W * $3/W = $44,460 for example.

You are purchasing, correct? Do not lease or PPA.

[ButchDeal]

So both are an issue? Is the 10.1 vs 10.4 a big issue on the optimizers, they say that's all they love ever used on those panels? I'm no electrician. They agreed I'd get trim but that the 11.4 was rated for 155% so it would be a loss of production at the best part of the day not a overload issue. They are looking into 2 smaller ones but reiterated there would be 3-5% loss, potentially harder to monitor and a small price difference.

Yes it is an issue and would void the warranty from SolarEdge.
Yes I figured it that that "is all they have ever used" some installers are lazy and my experience is the worst offenders tend to try to use the P400 for everything.
The P505 is new and so is the PV modules..

Also yes the SE11400H is rated to have up to 155% over sized but that does not make it always a good idea. In your case with all facing the same direction and no shadows it is a bad idea.
For someone else that might have half facing east and half facing west with a few shadows, it would be a good idea. SolarEdge allowed the flexability for that but it is not recomended to oversize that much in cases like yours.

The inverter and optimizers will be running a lot hotter than normal trying to manage the load and it would be a lot of loss of production.

There would be NO losses with two smaller inverters. There WILL be losses with the one undersized inverter.

The monitoring will NOT be any harder at all. They just link the two together and set up one for monitoring. SolarEdge has sites with a hell of a lot more inverters and easily monitors them.

[ButchDeal]

I strongly recommend the Solar Edge Consumption monitoring option. And be sure to use Ethernet for your uplink -- NOT cellular or Zigbee. The comms for the two inverters should be wired together via 485. I think only one Ethernet is required -- but I'm sure Butch will correct me if I am wrong.

When the Solar Edge Monitoring portal in configured correctly, it will be no more difficult to manage / understand what is going on than if you had only a single inverter.

I would recomend the consumption monitor as well
Also might be a good opportunity to ask for one or both of the inverters to have a built in EV charger

[adam61]

They switched to the 2 inverters at 7.6kW instead of the single 11.4kW, no cost to me. They still insisted the optimizers were fine, but were having their engineer check with SolarEdge.

Is the consumption monitor an upgrade I need to order or ask for? Are there any other things I should push for? My Tesla has a dedicated 100Amp (80Amp net) charger so that's not necessary. My panel is only 200 Amp so it's all line side tapped in the Solar PV design.

I'm at $2.65/w gross after a lot of negotiation so theres not much wiggle room.

[ButchDeal]

They switched to the 2 inverters at 7.6kW instead of the single 11.4kW, no cost to me. They still insisted the optimizers were fine, but were having their engineer check with SolarEdge.

Is the consumption monitor an upgrade I need to order or ask for?

it is an add on. You only need one of them to monitor consumption.

It is pretty clear cut and dry that that LG module is outside the operating range for the P400 and this is exactly why SolarEdge created the P505

Intact if you go to the Solaredge web based design tool it gives an error if you try to pair the LG390N2W to the P400 saying "Module Impp above the power optimizer max input current"
The P505 is the only one that it accepts.

[JSchnee21]

I think mine was a ~$500 add on. It has two CT's that measure consumption in your load center, and then it feeds the data into the inverter where it uplinks to the monitoring portal. For me, it's essential to see when my AC is running and how much I'm using versus making on a daily, monthly, and yearly basis. Yes, you can get some of this detail (monthly resolution) on your PoCo bill for free.

The only minor wrinkle when I had mine installed was that the monitor itself requires 240V power. So the electrician needed to install a small breaker to feed it in the external enclosure where it was installed. Could be installed in the house/garage, too, if you have room. Then only the comms need to run out to the inverter. Mine was one of the first my installer installed, so they weren't familiar with its requirements / setup yet,

https://www.solaredge.com/sites/default/files/system_owner_consumption_monitoring.pdf

If your installer bundled the Cellular modem for the inverter (most do) if you cut this it will roughly pay for the consumption monitoring. Ethernet or Ethernet (from the inverter) to a wireless bridge is a much better solution. With the Cellular option you get less detailed data (broader time slices) and the uploads are heavily delayed. Ethernet give 15min resolution with near real time (~30min) updates -- when the SE portal isn't lagging.

[adam61]

They changed to the P505's the engineer confirmed that was recommended and there was no cost to me, but reiterated the P400's had never had any issues. Have the 2 7600 SolarEdge inverters now. Also, switched to the 395w LG panels as the 390w are out of stock. No extra cost except the per watt cost there (38x5x$2.85=$541.50). Consumption Monitoring by Ethernet was included already they said it included an app and was connected to my home internet at all times could see each panel in real time and current usage. Hopefully, this is what you were discussing. All changes didn't change the $2.65/w cost gross installed. So should be good, I should see final design with changes mentioned by tomorrow. Thanks for the help!!

[JSchnee21]

Consumption monitoring is an optional add on unit separate from the inverter. Production monitoring via Ethernet is a standard feature of all SE inverters. You want both of these. Production measures what your PV makes. Consumption measures what your house uses -- I doubt they include it for free at that price. Most likely they don't know what it is.

Revenue grade metering is an upgrade to the inverted itself. Most folks in the USA don't need this as the PoCo generally replaces the home's electric meter with a bidirectional one.

[ButchDeal]

Revenue grade metering is an upgrade to the inverted itself. Most folks in the USA don't need this as the PoCo generally replaces the home's electric meter with a bidirectional one.

Revenue grade metering has nothing to do with net metering.

revenue grade meters are required for SRECs in mostly north east states which ALSO require a net meter from the power company.

[ButchDeal]

They changed to the P505's the engineer confirmed that was recommended and there was no cost to me, but reiterated the P400's had never had any issues. Have the 2 7600 SolarEdge inverters now. Also, switched to the 395w LG panels as the 390w are out of stock. No extra cost except the per watt cost there (38x5x$2.85=$541.50). Consumption Monitoring by Ethernet was included already they said it included an app and was connected to my home internet at all times could see each panel in real time and current usage. Hopefully, this is what you were discussing. All changes didn't change the $2.65/w cost gross installed. So should be good, I should see final design with changes mentioned by tomorrow. Thanks for the help!!

Totaly incredible that even after being explained the problem with the p400 they still insist in it. They never had a problem but have been installing them for close to a decade even as pv modules get more powerful year after year...
glad you got a decent quote in the end.

[adam61]

Do you have a link to what they likely bundled and what I want added re: consumption monitoring. They were pretty excited about what it had in Ethernet functionality, but are right they focused on each panel and other things, not my usage. Is this because it's texas and it's not real net metering and a line side tap so it doesn't know my usage? Or am I thinking about it wrong?? I know I have to buy a fake net metering plan (Green Mojntain Energy, M2, Reliant) as per Texas' 'F' net metering grade any other plan would see me use 2,500 produce 2,300 and instead of charging me 200 charge me the full 2,500 despite listing on the bill a big thanks for the 2,300 I sent back lol.

It's Oncor as provider. They are doing a 30% rebate, and then Fed rebate of 30% of the net of that so about 55% off net.

$39,800 (@$2.65/w*15.01kW)-$13,900 Oncor(they calculate it weird)-$7,800 Federal Credit on Net=$18,100 Net or $1.21/w, seems like a great deal and about the only way to get a reasonable ROI in Texas.