Panels for a 6.8 kw system

[ian04]

I'm in the planning stage of a 6.8 kw system in Northern California that will supply power for vineyard irrigation. I have three bids that all are around $32,000 which includes a site specific engineered ground mount. All three companies come with good recommendations and one I've done business with before on a non-solar electrical job. They all recommend using 25-27, 250-260W panels and Enphase M215 micro inverters claiming that will be the most efficient for my situation--I do not have a space or shade problem. I was little surprised that none of them suggested maximizers/string inverters and I'm debating whether I should seek more bids.

The three proposals offer me the choice of 7 different makes of panels, with a 'slight' cost adjustment for some of them. They appear to have identical warranties, etc. From this list are there ones you would avoid or favor? I don't mind paying a bit extra for better quality or for a brand that will be around.

ReneSola 156 poly 255W
Canadian Solar CS6P 255W or 260W
Q-Pro BFR-G3 260 BLK 260W
Sunmode plus 255 poly
CSUN 250W poly
Axitec AC-250W
Hyundai Solar HiS-S255MG-BK

Thanks for your help,
Ian

[silversaver]

Two system I monitoring in my area using both CS 255W and Hyundai 250W, both have excellent output.

https://enlighten.enphaseenergy.com/pv/public_systems/g7yQ437318#null/production/graph/days

https://enlighten.enphaseenergy.com/pv/public_systems/nsvH307960#null/graph/days

I'll talk with other installers if possible, they they are all offering the cheapest price panels to you....

[thejq]

If it's a grid tied system, $4.7/W sounds a little expensive for that combination of panels + micro inverter, even for ground mount. Maybe you should make some more calls. Start with solarreviews.com and yelp.com.

[foo1bar]

I'm in the planning stage of a 6.8 kw system in Northern California that will supply power for vineyard irrigation. I have three bids that all are around $32,000 which includes a site specific engineered ground mount.

I'd think string inverter would be more cost effective with no shade...
Maybe there's something unique about your situation though?

Since you're talking about vineyard irrigation, I'm thinking rural - so maybe you have some long distances? (which might actually be better done with the long wires being done in DC so they aren't carrying as much current.)

It's possible that the electricians want to only deal with what they know - which is AC. And enphase are pretty straightforward for someone who does residential electric, while string inverters would require them to do a little research to make sure they're doing everything right.

[SanDiego_installer]

Of the list you have provided, I prefer Canadian Solar. They have the highest PTC/STC ratio, an indication of real world performance. They have been manufacturing solar panels for 10+ years and are highly regarded. And I have installed thousands with zero issues.

If you want the most reliable system (we all do) and you have no shading, then request a quote using an SMA SB7000TLUS-22 inverter. SMA has a 30 year track record and will work flawlessly for the next 15-20 years. You can also purchase a 10 year extended warranty, for a total of 20 years, for under $600. Personally you will get nearly 20 years of use anyway, so the extended warranty may not be money well spent. The cost savings to switch from Enphase to SMA should be at least $1,700, not including the extended warranty. Keep in mind, if you have no shading, there is nothing to be gained from using Enphase.

A system with 25 micro inverters will have failures during it's lifespan, that's inevitable. You are adding more complexity and points of failure. Therefore a huge red flag should be that Enphase no longer covers labor in their warranty. That shows a complete lack of confidence in their product. Remember Enphase only has an 8 year track record and their second generation inverter failed miserably and they continue to do so. I know, I keep replacing them every month.

[ian04]

Thanks everyone for the help. I'm going to request quotes using a string inverter and see what I get.

Part of my problem is the support for the system is complicated. I need to fit it along a vineyard access road and partly over, but not supported by, a metal shed which means an L shape structure high enough at one end so a tractor can park under it. The installers I've talked to sub that out and it seems expensive. I'm considering building the structure myself and already have a $500 bid for the engineering. I have some of the materials on hand to build a PT post and beam structure--like a very basic unadorned pergola. I'm aware of the drawbacks of wood but I've got PT posts in my vineyard that are perfectly sound after 25 years even with irrigation. Also with bracing the posts won't have to be buried just fastened to a concrete foundation, at least according to the engineer.

I'm glad to get the recommendation for Canadian Solar. It was listed on two of my bids. One installer wants to use the CS6P 260W with Enfase 250 micro inverters. Wouldn't the 215's work just fine? Is the 250 the second generation?

Thanks again and on to more bids.

[sensij]

Yes, M215's would be fine with the 260 W panels. The M250's might generate slightly more, but not likely enough to cover their extra cost. You might want to get quotes both ways... if the installer doesn't price them any differently, then might as well use the M250's.

The fist generation was M175, the 2nd was M190, 3rd was M215, and 4th is M250. The M190 in particular seems to have developed a bad reputation for reliability, but the two more recent models have been holding up so far. Only time will tell...

[dat]

The new M215 IG (Intergrated ground) is better than the old M215 (obsoleted). I have Canadian Solar CS6P 255W with the new M215. This month, they produced 115% of the PvWatt's estimate.

[ian04]

After consulting with an engineer and getting feedback from a county planner I've had to make some adjustments--it's the 'two steps forward one step back process'. My original 'pergola' design proved to be expensive for what I would get out of it. I'll actually save money by using fewer but more powerful panels on a simpler structure--two rows of 11 or 12 each. One installer is suggesting using 22 LG300A1C-B3 with Enphase M250 microinverters. Any thoughts on that combination? Are there other 300W panels out there that I should consider? 72 cell panels are not going to work.

I got two bids using an inverter and both were about $1500 cheaper. The problem now is it looks like the county will require a small but significant shift in location that introduces a bit of shading. Whether it precludes the use of a string inverter or not is still being evaluated.

On researching the use of M250's I came across a recommendation to center-feed the branch circuit to minimize voltage rise in a fully-populated branch of 16 panels. Is this common done? Would it be a good idea for a branch of less than 16 panels?

I'm learning a lot from this project and want to thank you all again for your help.

[sensij]

One installer is suggesting using 22 LG300A1C-B3 with Enphase M250 microinverters. Any thoughts on that combination? Are there other 300W panels out there that I should consider? 72 cell panels are not going to work.

You probably mean LG300N1C-B3's. The A1C has the microinverter built in, and would not require the Enphase micros. The LG300's seem to be going at reasonable prices these days, I'm not aware of anyone else that is competing at that power level.

The LG300's pair well with the M250's. You'll see a little bit of clipping, especially this time of year, but the amount of energy actually lost over the course of the year is typically <1%.

On researching the use of M250's I came across a recommendation to center-feed the branch circuit to minimize voltage rise in a fully-populated branch of 16 panels. Is this common done? Would it be a good idea for a branch of less than 16 panels?

Sounds reasonable, especially if that configuration won't cost you any extra wire.