SolarEdge P320 vs P400? SE7600 vs SE10000?

[wildfins]

I am planning a 9.75kW DC solar system for our home and have spoken with a few companies in the past few weeks. All came back with quotes that might use different panels (31 x LG315 or similar) but all with the same SE7600 inverter (SE7600 max DC input = 10250W / max AC output = 7600W) and P320 as optimizers.

Would anybody please confirm if there are any benefits to upgrade to P400 from P320 (price difference is negligible as both are priced at $72-$76/ea)? e.g. just wonder whether the P400 is more reliable in the long run as it has more "headroom"?

Same question for SE7600 ($1700) vs. SE10000 ($2000)?

https://www.rexelusa.com/optimizers/...222-4294955466
https://www.rexelusa.com/residential...222-4294955466

[sensij]

I don't think the "headroom" matters much on the optimizers, the difference between them is related more to the voltage range of the panels they support. The LG315's will never need the voltage range offered by the P400, the P320 or P350 is fine.

On the inverter, going over 7600 W means that you will need a breaker larger than 40 A. Depending on the rating of your main service panel and its supply breaker, going over 40 A may require an MSP upgrade that typically costs $1500 or more.

You can see how much clipping you might encounter with the 9.75 kW on a 7600 W inverter by using PVWatts for your location and array orientation. Try "premium" panels, "roof mount", and 8% loss. In the Advanced parameters, set the DC to AC ratio to 1.0 for unclipped output, and to 9750/7600 = 1.28 to see the difference in production.

[wildfins]

Thanks sensij, I checked the spec again and the SolarEdge P320 is made to match 60-cell panels (LG315), P350 for 72-cell and P400 for 96-cell. All P-series optimizers come with 25-year warranty so P320 it is.

I also revised my power need and sized down the system to 9.4kW DC. I reran PVWatts using the settings that you suggested and got (15075kWh with DC/AC ratio = 1.0) vs. (15062kWh with DC/AC ratio = 9400/7600 = 1.24).

http://www.solaredge.com/files/pdfs/...zing_guide.pdf

Based on the above SolarEdge inverters guideline, oversizing up to 135% is allowed so I think that the ($1700) SE7600/40A breaker should do fine in this case where DC/AC = 9400/7600 = 124% while the total kWh output stays almost unchanged. However, I might still want to negotiate to get the ($2000) SE10000/60A breaker instead (and for the same price if possible ) as "oversizing would cause inverter to operate at high power for longer period, increase heating and hence might shorten its lifetime". The existing main panel is an Eaton 200A so it should be able to accommodate either model.

PS: The 9.4kW DC system size was originally obtained based on forum general recommended settings using (System Loss = 11%) and (DC/AC ratio = 1.24) for a total output of 14588kWh/year to match the 14540kWh/year power usage requirement for our home. By the way, are these PVWatts settings good enough or any other tweaks to match real-world application in SoCal area?

[wildfins]

SolarEdge inverters oversizing guideline high-lights:

"In many cases, oversizing the inverter, i.e. having more DC power than the inverter AC power, may increase power output in lower light conditions, thus allowing the installation of a smaller inverter for a given DC array, or alternately, installation of more DC power for a given inverter."
(...)
"SolarEdge allows DC/AC oversizing of up to 135%. Oversizing SolarEdge inverters will not harm the power optimizers or the inverters. Maintaining this limit ensures the lifetime of the inverter and is needed for keeping the inverter covered by its warranty."

see full specs attached...

[sensij]

Assuming your MSP is end fed, a 200 A panel is not rated to accept a 60 A pv breaker unless the main supply breaker is dropped to 175 A.

Unless you've got shade, I think you'll find 11% loss to be too high. 8% is what I would suggest, although year to year variation in weather can mask some of the differences. Also, if you run the numbers carefully, you might find that offsetting 100% of consumption is less cost effective than aiming somewhat lower.

[wildfins]

wow, did not know that SE10000 / 60A would require the main panel be derated down to 175A.

Actually, a sub-panel to be located on the opposite wall of the main panel inside the garage is also needed to feed our 2 EV 240V charging station and the 6kWh radiant floor heating system.
- In this case, is it possible to connect the SE10000 to the new 125A sub-panel instead (60A SE10K + 30A EV Charging + 30A Heat floor) w/o modifying the main 200A panel?
- Or it would be better to upgrade the main panel to 225A and just add a 100A sub-panel (30A EV Charging + 30A Heat floor)?

[sensij]

wow, did not know that SE10000 / 60A would require the main panel be derated down to 175A.

Actually, a sub-panel to be located on the opposite wall of the main panel inside the garage is also needed to feed our 2 EV 240V charging station and the 6kWh radiant floor heating system.
- In this case, is it possible to connect the SE10000 to the new 125A sub-panel instead (60A SE10K + 30A EV Charging + 30A Heat floor) w/o modifying the main 200A panel?

No, the 60 A PV breaker will be tested against the rating of all busbars (assuming you are NEC 2011 or earlier, see 705.12(D)(7)), so putting it in a subpanel won't help.

- Or it would be better to upgrade the main panel to 225A and just add a 100A sub-panel (30A EV Charging + 30A Heat floor)?

This would work as long as you don't go higher than a 200 A main breaker on the 225 A panel.

The system is on the large side... have you had an energy audit? You might find that putting some money into energy efficiency (insulation, etc) might help reduce your consumption to a level at which you would be more comfortable with the 7600 W inverter (and save some money by going with a smaller system).

[wildfins]

Thanks sensij, I have been reconsidering different options based on your feedback as well as other forum posts. I think that I will keep it simple by just going with a 9.4kW DC system and the SE7600 w/o modifying the existing main panel to save costs (124% oversizing or 119% with 96% efficiency) as I can always buy extended warranty for the inverter ($300-$460) if longevity is a concern.

[schmoot]

I don't think that the LG panels are compatible with the P400, due to the higher Isc, the LG panels have a Isc of 10.02, and the P400 can only accept a max of 10.0, the P320 allows for a Isc of 11A.

[schmoot]

SolarEdge is updating the specs on their P400 optimizers for 2016, they now officially support 10.1A Isc, so would be compatible with the LG315 panels.