Sanity check for a new system (San Diego)

[J.P.M.]

Here are some real world data after running the system for about 2 weeks. Last Saturday (Aug 23rd) had been the best day in terms of production so far. My 3.9kW (13 LG300 + 13 Enphase M250) system produced a total of 25.5kWh energy for that day. That is about 6.538kWh per kW of installed panels. Since I paid the extra $250 for the individual panel data access from Enphase, I also got some individual panel data. Both East and West facing panels produced roughly 1.97kWh for each panel for that day. South facing panels produced 2.07kWh per panel.

- East facing panels (97 degree az.): 10:30a to 12:45a or roughly 2 hours and 15 minutes where M250 "peaked" at 250W AC output. Assuming 265W AC theoretical max output, so 15W * 2.25 hours = 33.75Wh or roughly 1.7% of total output (33.75 div 1970).

- South facing panels (187): 11:30a to 2:45p or roughly 3 hours and 15 minutes peaked. 15W * 3.25 hours = 48.75Wh. 2.4% lost.

- West facing panels (277): 1:15p to 3:15p or roughly 2 hours peaked. 1.5%.

So the LG300 + M250 combo definitely clips in San Diego. LG285 or less panel is probably a better fit with the M250. However, this is the "worst" day in terms of clipping for these 2 weeks. Most of the days the clipping are shorter or non-existent.

According to Enphase's website, I am about 17% over PVWatt's estimated output. Of course 2 weeks is too short of a time frame to draw anything meaningful. That said, I am still more than happy with the output I am getting.

Thank you for the info and the consideration.

1.) I'm not surprised by the results. For San Diego anyway, SAM actually predicts that a LG 300 equipped array will outperform a S.P. 327 array of similar size, if clipping does not occur.

2.) New & clean, you'll clip more this time of year than in, say winter, due to the sun angles, with more clipping in the spring for sim. angles but generally lower temps. I'll stand by my SWAG of 150 to 300+ hrs. of clipping/yr., depending on orientation+/- 10-20% or so. .

3.) You may clip a bit less after the 3% 1st yr. burn in, and less with larger solar zenith angles late fall to early spring.

4.) I'd note, as several others besides me have found, your find that PVWatts underpredicts output at least on a clear day. If you rerun and check hourly output from PVWatts for a clear day near 08/23, you'll get a SWAG of how much overestimation and/or a dart throw of what the PVWatts correction factor needs to be to get closer to reality.

5.) I'd also note that your LG 300 output/installed kW (6.54 kWh/kW) is higher than at least one S.P. array in S.D. which faces at 195 deg., (mine (6.24 kWh/kW)) for that day. I've got 2 months of dirt on mine as I'm running fouling tests and S.P. claims a 5%/-3 tolerance. Anyway, IMO, your #'s seem to add support, even if anecdotally, that most (similar sized) arrays have the same or close output.

Thanx again for the info.

[silversaver]

Here are some real world data after running the system for about 2 weeks. Last Saturday (Aug 23rd) had been the best day in terms of production so far. My 3.9kW (13 LG300 + 13 Enphase M250) system produced a total of 25.5kWh energy for that day. That is about 6.538kWh per kW of installed panels. Since I paid the extra $250 for the individual panel data access from Enphase, I also got some individual panel data. Both East and West facing panels produced roughly 1.97kWh for each panel for that day. South facing panels produced 2.07kWh per panel.

- East facing panels (97 degree az.): 10:30a to 12:45a or roughly 2 hours and 15 minutes where M250 "peaked" at 250W AC output. Assuming 265W AC theoretical max output, so 15W * 2.25 hours = 33.75Wh or roughly 1.7% of total output (33.75 div 1970).

- South facing panels (187): 11:30a to 2:45p or roughly 3 hours and 15 minutes peaked. 15W * 3.25 hours = 48.75Wh. 2.4% lost.

- West facing panels (277): 1:15p to 3:15p or roughly 2 hours peaked. 1.5%.

So the LG300 + M250 combo definitely clips in San Diego. LG285 or less panel is probably a better fit with the M250. However, this is the "worst" day in terms of clipping for these 2 weeks. Most of the days the clipping are shorter or non-existent.

According to Enphase's website, I am about 17% over PVWatt's estimated output. Of course 2 weeks is too short of a time frame to draw anything meaningful. That said, I am still more than happy with the output I am getting.

As I recall reading one of Enphase whitepaper, undersizing inverter yield better overall output and I believe that since I did get better output undersizing my central SMA inverter. I use a 6KW for 7.1kW array

[AMCSquared]

For the Enphase M250's, same format as prior:

1.) New, clean:

97 deg. az.: 479 kWhrs/yr. per panel, 1.9 kWhrs./yr. lost to clipping, 0.4%, 190 hrs. >0 W clipping.

187 deg. az. : 552 , 4.3 , 0.8%, 336

277 deg. az. : 481 ,1.2 ,0.2%, 146

2.) Same but 3% dirt, 3% burn in reduction after 1st yr.


97 deg. az.: 472 kWhrs./yr per panel, .1 kWhrs/yr. lost to clipping, 0.1%, 36 hrs. > 0 W clipping.

187 deg. az.: 523 , 0.8 , 0.2%, 101

277 deg. az.: 454 , 0.1 ,0.0%, 19

Again, my apologies for my error.

One possible saving grace for my embarrassment: Both of the above may serve as SOME comparison between M215's and M250's.

Here are some real world data after running the system for about 2 weeks. Last Saturday (Aug 23rd) had been the best day in terms of production so far. My 3.9kW (13 LG300 + 13 Enphase M250) system produced a total of 25.5kWh energy for that day. That is about 6.538kWh per kW of installed panels. Since I paid the extra $250 for the individual panel data access from Enphase, I also got some individual panel data. Both East and West facing panels produced roughly 1.97kWh for each panel for that day. South facing panels produced 2.07kWh per panel.

- East facing panels (97 degree az.): 10:30a to 12:45a or roughly 2 hours and 15 minutes where M250 "peaked" at 250W AC output. Assuming 265W AC theoretical max output, so 15W * 2.25 hours = 33.75Wh or roughly 1.7% of total output (33.75 div 1970).

- South facing panels (187): 11:30a to 2:45p or roughly 3 hours and 15 minutes peaked. 15W * 3.25 hours = 48.75Wh. 2.4% lost.

- West facing panels (277): 1:15p to 3:15p or roughly 2 hours peaked. 1.5%.

So the LG300 + M250 combo definitely clips in San Diego. LG285 or less panel is probably a better fit with the M250. However, this is the "worst" day in terms of clipping for these 2 weeks. Most of the days the clipping are shorter or non-existent.

According to Enphase's website, I am about 17% over PVWatt's estimated output. Of course 2 weeks is too short of a time frame to draw anything meaningful. That said, I am still more than happy with the output I am getting.

[wrlsguy]

I don't have a disconnect up on my roof. Mine is next to my electrical panel.

Will the utility actually come out, or are they just waiting for the city inspection? Let us know if your city inspector actually gets onto the roof.

SCE was waiting for a copy of my city approval and then they mailed me a permission to operate. There was an inspection months later for the CSI rebate verification. I wouldn't be surprised if your system was left on accidentally after the city inspection.

https://enlighten.enphaseenergy.com/...ems/XeXh243874 is the public Enlighten page for my system, and I am running 16x250w with M215s. Today was a good solar day for me. I got 24 kWh.

[AMCSquared]

Congrats on the start. Did they tell you which brand(s) they were using for mounting? The rails look like super strut that you can get at Home Depot. I'm curious because when I installed in Irvine, all the mounting hardware (roof hooks, rails, and clamps) had to be from the same manufacturer, per the city inspector. I suspect it was a city liability thing as manufacturers typically have a PE certify their own branded complete racking solutions.

Sorry, didn't know what the brand is for any of the mounting materials. I did briefly see the engineering drawings (ones submitted to the city), but I didn't notice any brand information. You are correct to say that the super struct looks awfully like the stuff you can get from Home Depot. Couple more pictures of the finished install (hopefully they show up OK, I had to do some "tricks" on DropBox for the pictures to work in the forum).

The system is 13 x LG300 and 13 x Enphase M250. They did briefly turn the system on for testing. It was producing about 2.5kW AC around 3:30PM (system is 3.9kW DC). This is according to my whole house usage meter (about 2.0kW going into the grid plus another 0.5kW for the usage right before turning it on). The company will install the Envoy monitoring gateway once we receive permission to operate from SDG&E.

Now just waiting for city and SDG&E inspections.


6 panels facing west:



2 Facing south and 5 facing east:



This is at the end of the string. It does have an on/off switch. AC disconnect?



Anchor underneath the flat concrete roof tile.

[wrlsguy]

Some updates. Company "S" started the installation today. It was going to be an one day job, but some of the workers was out sick today. So two dudes did as much as they could today. This includes all the anchors, railing, and the Enphase M250 micro-inverters. They also did about 80% of the conduits from the electrical panel to the 2nd floor roof.

West facing roof (6 panels)
[ATTACH=CONFIG]4488[/ATTACH]

East facing roof (5 panels)
[ATTACH=CONFIG]4489[/ATTACH]

There are 2 more south facing roof (sorry, no picture).

Congrats on the start. Did they tell you which brand(s) they were using for mounting? The rails look like super strut that you can get at Home Depot. I'm curious because when I installed in Irvine, all the mounting hardware (roof hooks, rails, and clamps) had to be from the same manufacturer, per the city inspector. I suspect it was a city liability thing as manufacturers typically have a PE certify their own branded complete racking solutions.

[russ]

Good to see your progress!

[AMCSquared]

Some updates. Company "S" started the installation today. It was going to be an one day job, but some of the workers was out sick today. So two dudes did as much as they could today. This includes all the anchors, railing, and the Enphase M250 micro-inverters. They also did about 80% of the conduits from the electrical panel to the 2nd floor roof.

West facing roof (6 panels)
image-10.jpeg

East facing roof (5 panels)
image-11.jpeg

There are 2 more south facing roof (sorry, no picture).

[J.P.M.]

Please do not apologize. You are doing me and the rest of the community a favor. So Enphase is not totally disingenuous to quote 300W for the M250. Basically I would be loosing about 31kWh (a tad over $5) for the first year. That is almost statistically insignificant. By year 2, clipping become virtually a non-issue.

Not totally, at least by my estimate for this application. But opinions vary as do applications, and while I have confidence in my #'s and believe them to be reasonable, I could still be wrong.

[AMCSquared]

For the Enphase M250's, same format as prior:

1.) New, clean:

97 deg. az.: 479 kWhrs/yr. per panel, 1.9 kWhrs./yr. lost to clipping, 0.4%, 190 hrs. >0 W clipping.

187 deg. az. : 552 , 4.3 , 0.8%, 336

277 deg. az. : 481 ,1.2 ,0.2%, 146

2.) Same but 3% dirt, 3% burn in reduction after 1st yr.


97 deg. az.: 452 kWhrs./yr per panel, .1 kWhrs/yr. lost to clipping, 0.1%, 36 hrs. > 0 W clipping.

187 deg. az.: 523 , 0.2 , 0.8%, 101

277 deg. az.: 454 , 0.1 ,0.0%, 19

Again, my apologies for my error.

One possible saving grace for my embarrassment: Both of the above may serve as SOME comparison between M215's and M250's.

Please do not apologize. You are doing me and the rest of the community a favor. So Enphase is not totally disingenuous to quote 300W for the M250. Basically I would be loosing about 31kWh (a tad over $5) for the first year. That is almost statistically insignificant. By year 2, clipping become virtually a non-issue.

[J.P.M.]

Really no good reason other than all the San Diego installers quotes Enphase.

On a side note, here is one San Diego system on PVOutput with similar LG300 + M250 combo. There appears to be clipping around 11:50AM to 1:50PM. So about two hours worth of "flat top" on the bell curve. If I had to guess, the system "lost" at most 0.42kWh ((265W AC theoretical max output minus 250W) * 14 panels * 2 hours) due to clipping or about 1.5% of total output (0.42 div 28.4). I picked the "worst" day in terms of hours of clipping from the data available.

So there will absolutely be clipping with the LG300 + M250 combo in San Diego. However, I really don't think couple percentage points is a big deal. I bet this particular system will not see much clipping after 2 or 3 years worth of usage (due to panel degradation).

Based on my last post to this thread, FWIW, I agree w/ your estimate.

[J.P.M.]

06/09/2014 :SCRAP THE INFO BELOW - IT'S FOR THE ENPHASE M215'S. M250'S TO FOLLOW. I apologize for the error.

All only a bit better than SWAGS and all figures are per panel, NO SHADING 18 deg. el.(tilt):

1.) New, clean, no dirt, no burn in tolerance, assume 250 Watt clip point on the Enphase:

Output/panel,hrs. w/some clipping, kWhrs./yr. lost, and % lost from clipping"

97 deg. az: 464 kWhrs./yr. per panel, 16.4 kWhrs./yr. lost to clipping, 3.5%.

187 deg. az.: 529 , 27.3 , 5.2%

277 deg. az: 468 ,13.95 , 3.0%


2.) Same but with 3% dirt reduction, 3% burn in reduction at end of 1st yr.


97 deg. az.: 452 kWhrs./yr. per panel, 8.33 kWhrs./hr lost to clipping, 1.9%

187 deg. az. 509 ,14.9 , 3.00%

277 deg. az. 447 , 6.76 , 1.5%


Using TMY3 data for Miramar, 1.3% wiring losses, 96.5 inverter eff. All figures are per panel, LG 300 using published specs.

Because the array will be oversized (at least initially), most of the clipping penalty will cost you at tier 1 rates. Using latest rates in effect 05/01/2014, the blended clipping cost penalty will be about $.17/kWhr.

After the 1st yr. drop the penalties by .7% yr. for SWAG of how long the clipping penalty will cost you money.

SWAG on # of hrs. SOME clipping (>0 W) will occur varies w/condition and orientation from 423 hrs/.yr. at 277 deg, dirty to 939 hrs./yr. new & clean at 187 deg.

For the Enphase M250's, same format as prior:

1.) New, clean:

97 deg. az.: 479 kWhrs/yr. per panel, 1.9 kWhrs./yr. lost to clipping, 0.4%, 190 hrs. >0 W clipping.

187 deg. az. : 552 , 4.3 , 0.8%, 336

277 deg. az. : 481 ,1.2 ,0.2%, 146

2.) Same but 3% dirt, 3% burn in reduction after 1st yr.


97 deg. az.: 472 kWhrs./yr per panel, .1 kWhrs/yr. lost to clipping, 0.1%, 36 hrs. > 0 W clipping.

187 deg. az.: 523 , 0.8 , 0.2%, 101

277 deg. az.: 454 , 0.1 ,0.0%, 19

Again, my apologies for my error.

One possible saving grace for my embarrassment: Both of the above may serve as SOME comparison between M215's and M250's.

[AMCSquared]

Quick question...how come you decided to go with Enphase over SolarEdge?

Really no good reason other than all the San Diego installers quotes Enphase.

On a side note, here is one San Diego system on PVOutput with similar LG300 + M250 combo. There appears to be clipping around 11:50AM to 1:50PM. So about two hours worth of "flat top" on the bell curve. If I had to guess, the system "lost" at most 0.42kWh ((265W AC theoretical max output minus 250W) * 14 panels * 2 hours) due to clipping or about 1.5% of total output (0.42 div 28.4). I picked the "worst" day in terms of hours of clipping from the data available.

So there will absolutely be clipping with the LG300 + M250 combo in San Diego. However, I really don't think couple percentage points is a big deal. I bet this particular system will not see much clipping after 2 or 3 years worth of usage (due to panel degradation).

[J.P.M.]

Thanks for the offer. Before wasting more of your time, I am pretty much set on the LG300 + M250. My gut feeling is that I may see minimum clipping with brand new panels. However, degradation of the panels within the first couple years will minimize if not totally eliminate such clipping. It would be interesting to see what the theoretical calculation would be. I can report back once the system is installed (I already signed the purchase contract). Yes, I also paid for the individual panel monitoring so I will be able to report back to see if theory matches reality.

I am located at the western part of PQ (i.e 56 between 5 and 15). As is, I will have 1.2KW (4 panels, not all together) facing South-ish (187 degrees), 1.5KW facing West (not all together again, 277 degrees), and 1.2KW facing East (97 degrees). My roof is 18 degrees. Due to the complexity of my roof, micro inverter is probably one of the easiest solution for me.

If we trust PVWatts, there are only a few days (and only an hour or so for these days) where the panel output will approach the theoretical limit of M250.

06/09/2014 :SCRAP THE INFO BELOW - IT'S FOR THE ENPHASE M215'S. M250'S TO FOLLOW. I apologize for the error.

All only a bit better than SWAGS and all figures are per panel, NO SHADING 18 deg. el.(tilt):

1.) New, clean, no dirt, no burn in tolerance, assume 250 Watt clip point on the Enphase:

Output/panel,hrs. w/some clipping, kWhrs./yr. lost, and % lost from clipping"

97 deg. az: 464 kWhrs./yr. per panel, 16.4 kWhrs./yr. lost to clipping, 3.5%.

187 deg. az.: 529 , 27.3 , 5.2%

277 deg. az: 468 ,13.95 , 3.0%


2.) Same but with 3% dirt reduction, 3% burn in reduction at end of 1st yr.


97 deg. az.: 452 kWhrs./yr. per panel, 8.33 kWhrs./hr lost to clipping, 1.9%

187 deg. az. 509 ,14.9 , 3.00%

277 deg. az. 447 , 6.76 , 1.5%


Using TMY3 data for Miramar, 1.3% wiring losses, 96.5 inverter eff. All figures are per panel, LG 300 using published specs.

Because the array will be oversized (at least initially), most of the clipping penalty will cost you at tier 1 rates. Using latest rates in effect 05/01/2014, the blended clipping cost penalty will be about $.17/kWhr.

After the 1st yr. drop the penalties by .7% yr. for SWAG of how long the clipping penalty will cost you money.

SWAG on # of hrs. SOME clipping (>0 W) will occur varies w/condition and orientation from 423 hrs/.yr. at 277 deg, dirty to 939 hrs./yr. new & clean at 187 deg.

[HX_Guy]

Quick question...how come you decided to go with Enphase over SolarEdge?