Advice on Residential Solar proposals (San Diego)

[robertwinz]

I'm looking at getting solar for my house. I've had proposals from 5 different installers and have narrowed it down to a few preferred options. They're actually very similar, but I would appreciate any inputs.

Option 1:
16 x Sunpower 327 panels
Sunpower (SMA) string inverter
Sunpower rack mounting
5.232 kW DC
Installer kWh estimate = 8443 kWh / year
PVWatts.com estimate = 8519 kWh / year (premium panels, 10% system loss)
~$4.40 / kW before tax credit

Option 2:
16 x Sunpower 327 panels
SolarEdge SE5000A-US w/ optimizers
Not sure on mounting
5.232 kW DC
Installer kWh estimate = 8427 kWh / year
PVWatts.com estimate = 8519 kWh / year (premium panels, 10% system loss)
~$4.65 / kW before tax credit

Option 3:
17 x LG 315 Panels
SolarEdge SE5000A-US w/ optimizers
Not sure on mounting
5.36 kW DC
Installer kWh estimate = 8589 kWh / year
Haven't done PVWatts.com estimate for this system, but it's more or less the same as Option 2 in DC kW and the installer estimates seem reasonable.
~$4.00 / kW before tax credit


I have a few specific questions / concerns:

1. Price! Is this reasonable for San Diego?

2. The LG warranty is ambiguous: the module warranty is 12 years, but the performance warranty is 25 years. The installer I asked about that today said LG has told them then the 12 year period applies to "factory defects"... but what would cause performance to fall out of spec other than a factory defect? So I'm just not sure where I would stand with the LG warranty.

3. I've been told that the Sunpower panels will start producing power about 30 mins earlier in the morning and for about 30 mins later in the afternoon than other panels. Anyone have any experience with this?

4. One installer told me that they have not installed any gen 3 SolarEdge inverters because the first two generations had so many issues (100% 1st gen installations replaced, 60% gen 2 replaced), so they're waiting for more evidence that gen 3 has fixed the problems. He also said that in my case where there are no shading issues there would be no advantage to the SolarEdge w/ optimizers anyway. Sounds reasonable to me, can anyone comment on this?

Thanks in advance for all advice!

[J.P.M.]

I've got the same #/type/mfg. as your options 1 & 2. SAM and my own est. come out at ~ 9,300 - 9,500 kWh/yr. @ 18.5 deg. tilt, 195 deg. az. PVWatts is a bit light, even at system losses at 10%.

This doesn't mean much, but my 1st yr. actual production was 9,594 kWh, 2d yr. was 9,032 kWh. 2d yr. had about 6% less insolation.

According to SAM, LG 300's will match the SP's annual output in terms of kWh/yr. per nameplate kW. I haven't run the LG315's on SAM, but they may do better yet.

FWIW, I'd see if I couldn't get the LG 300's or 305's for closer to $3.50/Watt. as others around here have done. $4.00/Watt for the 315's seems high, especially since the year end scramble is over and the ITC and NEM issues seem to be settling down.

Panels produce power when the sun shines. that earlier production smack is B.S., and anyway, early morning production is usually about squat. Today, the sun broke the horizon at my house at 7:07 A.M. Production through 7:40 A.M. was 0.23 kWh. Day total was 22.48 kWh with about a 1.1 kWh shading loss after 3 P.M.The generation on the tails of the day are relatively small, making the diff. in output, such as it may exist, from one mfg. panel to the next close to miniscule.

Opinions vary, but w/ no shading I'd go w/ the SMA and LG 300's or 305's and shoot for $3.50/Watt. Call around.

Sunpower's good stuff, but for a buck/Watt, or ~ $0.70 /Watt after ITC, ~ $3,500 is a lot for not much more than bragging rights and equal annual output.

[sensij]

With regard to question 4, the installer might be mixing up Enphase and SolarEdge. Early generations of Enphase products have had higher failure rates, but more recent designs seem to be holding up better. SolarEdge optimizers have had a design spin or two, but other than what Solarix has reported from some early product testing, the rate of infant mortality in the optimizers seems low. Many SolarEdge systems have been installed by forum members in the last couple years and most have been working fine (including mine).

If you are leaning toward a string inverter, I would give the Fronius Primo series a close look... less expensive than SMA's stuff, but with better data access and at least on paper, functionally equivalent except for missing the grid-down secure power supply.

To put it bluntly, the sunpower salesman is feeding you a load of B.S. At those prices, you should be getting the 335's or 345's, not 327's, and even then it is probably still higher than some.

[robertwinz]

Thanks for both the replies.

Regarding production: I'll have 6 panels at 170 az. and the rest (up to 13) at 260 az, 18.5 tilt.


What is SAM?


LG 305s is an interesting idea - if I assume that the total output drops by 305/315 then that takes me to 8316 kWh nominally, which is right on target.


Regarding inverters: he definitely meant SolarEdge - he specifically said that the issue was with the optimizers overheating. I'll ask the other contractor if they're familiar with that issue.

Someone else pointed out that SolarEdge gives you the advantage of individual monitoring of panels, thoughts on that?


What do people think about warranties? I have a couple of things I can't decide on:

1. Do I care that the SPR warranty is 25 years vs the LG 12 years? Like I said, I don't really even understand the LG warranty. But chances are that most if not all the LG panels are going to last much longer than 12 years if that's the warranty period, and the ROI isn't too bad even if the system died completely after 12 years, which isn't going to happen. OTOH, if I were to sell the house in 10 years (you never know) then having 15 years left on the warranty is going to look a lot better than 2.

2. Option 1, which is the all SPR system, comes with a production warranty from SPR, guaranteeing 97.5% of predicted output and reimbursed at actual cost. I'm pretty skeptical about these production warranties - I'm sure the estimates are very conservative to the point that if it wasn't met then there would be something seriously wrong that would be covered by the individual parts warranties and (hopefully) fixed quickly. The other options also have a production warranty, but not as good on paper.

[J.P.M.]

For my part, you're welcome.

SAM = System Advisor Model. It's PVWatts on steroids. It uses the same weather data, but gets much more detailed than PVWatts in the analysis, both from an engineering and economic standpoint. The output is also more detailed. The results seem to match reality a bit better. Still, unless you really know what you're doing it can be like giving a 2 yr. old a loaded pistol. I only mentioned SAM in my response as a comparison in the sense that PVWatts spits out about 8,800 kWh/yr. for my stuff vs. SAM's ~ 9,400 kWh/yr.

On warranties, S.P. does have a good one - for which you will pay a high up front premium of ~ 20+ % or so. Also, the way it looks now, quality panels will last a long time - S.P's or anyone else's, giving warranties a lower probability of being needed and more expensive ones like S.P.'s closer to overkill.

As I wrote, you want extra (IMO overkill) buy an extended warranty - buy the LG's and an extended warranty - it's cheaper, and the quality will still be as good.

At the end of the day, all warranties are marketing tools, particularly production warranties. From the discussion about output above, note that output is, just like and mostly because of the weather, variable. Next, how do you verify a drop in output ? Read the S.P. warranty, particularly the verification part(s). Performance of any system will decrease somewhere between probably 2 and 5 % or more simply due to dirt, and it won't take long. Even if in writing, that 97.5% is B.S. with more holes than swiss cheese.

Your skepticism is well placed and well considered. You have a lot of company in that regard.

A respectful suggestion: Download and read "Solar Power Your Home for dummies". Free on the net.

You're going in the right direction, but knowledge is power. Read the book and you'll know more than about 90% of the peddlers who are trying to get in your knickers.

[solarix]

imho, Sunpower sells hype for a premium price. PV panels are a commodity anymore, pick any name brand and negotiate for best $/w. The most important consideration on inverters is reliability, reliability, reliability - and SMA is the only brand I trust anymore. I know the People's Republic of CA is a higher standard of living but prices here are below $2.75/watt

[Drastyn]

WoW , I’m not in US-market so I’m not aware of prices, but in my opinion this price is something crazy also for a Sunpower. In EU this same plant Option 1:
16 x Sunpower 327 panels
Sunpower (SMA) string inverter
Sunpower rack mounting
5.232 kW DC
Installer kWh estimate = 8443 kWh / year
PVWatts.com estimate = 8519 kWh / year (premium panels, 10% system loss)

will cost not more than 2.200 €/kWp before tax credit.

[darinf]

We just got our solar installation done in San Diego.

Forgive the newbie question, but how are you calculating cost per kW? Is it just the total cost of the system divided by the size of the system in kW DC?

If I have a 10540 watt DC system, do I just divide the total cost by 10540? Or is there some other way to calculate it? If that's it, then our system costs $3.25/kW.

We have 34 LG 310 panels with Enphase M215 inverters. (Yes, we use a lot of power...)

Anyway, our installer was awesome and the whole thing from the day I e-mailed them to book to the day we flipped the switch on with SDG&E was about 40 days total.

[ButchDeal]

We just got our solar installation done in San Diego.

Forgive the newbie question, but how are you calculating cost per kW? Is it just the total cost of the system divided by the size of the system in kW DC?

If I have a 10540 watt DC system, do I just divide the total cost by 10540? Or is there some other way to calculate it? If that's it, then our system costs $3.25/kW.

We have 34 LG 310 panels with Enphase M215 inverters. (Yes, we use a lot of power...)

Anyway, our installer was awesome and the whole thing from the day I e-mailed them to book to the day we flipped the switch on with SDG&E was about 40 days total.

it is price per WATT not KW. so you divide the total price by the total watts. In your case you have $3.25/w
I would question the quality/integrity of an install that put in LG310 modules with M215 optimizers:

https://enphase.com/en-us/products-and-services/microinverters

[Yaryman]

We have 34 LG 310 panels with Enphase M215 inverters. (Yes, we use a lot of power...)

Did they really put Enphase M215's on that system?
As ButchDeal mentioned, those are undersized for those panels.

Worse yet, a quick search for prices ( retail ) of the M215's and M250's show them to be about the same price.

[darinf]

it is price per WATT not KW. so you divide the total price by the total watts. In your case you have $3.25/w
I would question the quality/integrity of an install that put in LG310 modules with M215 optimizers:
https://enphase.com/en-us/products-a...microinverters

Did they really put Enphase M215's on that system?
As ButchDeal mentioned, those are undersized for those panels.

Worse yet, a quick search for prices ( retail ) of the M215's and M250's show them to be about the same price.

Thanks for the feedback on my system.
Sorry about hijacking this thread...

But I talked to my installer and here's the explanation he gave me: (I hope I am explaining this right)

Our breaker panel is maxed out, so he could fit 30 M250 inverters (250W) or 34 M215 inverters (225W).
Yes, we have 34 LG310 panels, but he said that due to the azimuths and angles of our roof, it would be very unlikely that all the panels ever hit their ideal max output of 250W per panel.
So, rather than have 30 panels that might rarely hit full capacity, he would rather have 34 panels outputting during non-ideal perfect conditions.

This is hard to explain...

Say there's a few days out of the year where the sun is at the right angle so that the panels could be outputting 250W. Yes, during those days, the M215 inverters would be clipping and I am in theory "losing" 25W on each panel (compared to the M250's) that is facing the sun at an ideal angle. This "ideal" time is also not during the whole day, but just during a small window of time during that particular day. (How often do panels hit their max? I have no idea.)

But, for all the other times, the extra 4 panels could be generating a lot more power than I would be losing on those few days where they could be outputting 250W.

So he would rather "lose" the amount of generation that is clipped some of the time but gain the generation from the extra 4 panels all the time.

If say the 15 panels that I have that are facing at an ideal angle for one day, for one hour, I would be clipping out 25Wx15 panels = 375Wh lost, but during that same day, suppose the extra 4 panels are outputting 225W during that same 1 hour period. That's an extra 900Wh. So even with the clipping, I would still be getting 525Wh more than I would if I had 30 panels with M250's. And this is just for one hour of one day.

For all other days where none of the panels are hitting over 225W, then I am not clipping or losing anything and I am getting 4 more panels worth of generation.

Does this make sense? It made sense to me when he explained it and drew some graphs. (Maybe some of my assumptions are off.)

[Yaryman]

Darinf, thanks for replying. What direction do your panels face? From the description you gave, it sounds like many face East or West,
with the panels that might max out facing South.

[J.P.M.]

Darinf: How about starting a new thread ?

In the mean time, in retrospect, it might have been better to upgrade service. The price diff. of the Enphase 215 vs. 250 isn't that much. As for how much clipping, that's always an estimate, and anyway variable, yr./yr.

Provide zip, system size and wattage per orientation. A few of us can take a SWAG at clipping penalty in kWh/yr. Or, self help: Use PVWatts and use the advanced parameters DC to AC size ratio, following the instructions.

[ButchDeal]

Darinf: How about starting a new thread ?

In the mean time, in retrospect, it might have been better to upgrade service. The price diff. of the Enphase 215 vs. 250 isn't that much. As for how much clipping, that's always an estimate, and anyway variable, yr./yr.

Provide zip, system size and wattage per orientation. A few of us can take a SWAG at clipping penalty in kWh/yr. Or, self help: Use PVWatts and use the advanced parameters DC to AC size ratio, following the instructions.

My thought was not so much at price difference between M215 and M250 but that with M215 you could use lower cost modules like 300W or even 280w for nearly the same production as the LG310w. That would have a cost saving.

[J.P.M.]

My thought was not so much at price difference between M215 and M250 but that with M215 you could use lower cost modules like 300W or even 280w for nearly the same production as the LG310w. That would have a cost saving.

+1. I hadn't thought of that.