Sanity check for a new system (San Diego)

[AMCSquared]

Ain't competitive bidding great ?!

I forgot to add that SDG & E allows (Actually, I think is mandated by CPUC) customers like you & I to try T.O.U. for a period of time & revert to "DR" (tier) schedule if we think T.O.U. sucks.

Sometimes vendors get slippery about pricing on long lead time jobs. FWIW, I'd suggest being doubly sure about escalators built into/buried in the contract. Caveat Emptor.

Oh: and make sure you do indeed get LG 300's for your money. Trust but verify. Read each nameplate and confirm for yourself w/ a good eyeball that they're not LG 260's - LG 290's. Sometimes mistakes happen.

Yeah, I think I saw on one of the form for T.O.U which states that we have the right to revert back to DR schedule after receiving the 1st T.O.U bill. Otherwise you are locked in for 12 months. Isn't the whole point of the "Smart Meter" that we get real-time consumption and be able to change the way SDG&E bill us us on the fly?

Company "S" contract is pretty straight forward. No hard to understand legalese. I will definitely double check the actual goods delivered.

I will update this thread once there are more interesting things happening. Please do PM me if anyone wants the exact company behind all these alphabet soup names.

[J.P.M.]

Two companies were bidding using LG300 panels. Another one was bidding with LG275 (and variations of LG2xx). Outside of SunPower, LG seems to be popular currently within San Diego. I didn't specify panel brand initially (except to say I did NOT want the premium SunPower). I am guessing there is still ample supply of LG panels locally.

I did size the system up from a 3kW to a 3.9kW system to accommodate the Prius Plug-In. I know, not a "true" EV, but close enough. Funny this whole project got kick started due to the purchase of the Prius. Also, we figured if we ever get a Tesla-like EV (something with "practical" battery range and not costing $100K fully loaded), we can always use EV related rate from SDG&E. It is harder to justify PV's cost to replace Tier 1 or T.O.U's lower rate. Replacing Tier 3 and 4's $0.37+ / kWh rate? Easy decision.

LG 300 availability - I haven't seen any installed in my neighbor yet. Hope/Maybe I'm wrong. Some vendors claim a private stock. Don't be surprised if you get a call.

[AMCSquared]

LG 300 availability - I haven't seen any installed in my neighbor yet. Hope/Maybe I'm wrong. Some vendors claim a private stock. Don't be surprised if you get a call.

Not having any personal insight on solar panel distribution channels, I have to rely on the contractor's word that they can get what they sold. Maybe both companies utilize the same upstream distributor and there is a bunch of LG's in the warehouse? It's just weird that almost all the vendor's I contacted quoted LG panel of some sort (I didn't specify LG). Only one company quoted something else, but they only utilize their own brand.

I am going to raise hell if they can't get what they sold, but I am not going to worry about availability right now. I will cross that bridge when I get there.

[SanDiego_installer]

LG 300's are currently in-stock in San Diego, no issue there. Keep in mind this configuration will result in "clipping", which is a shame because the cost per watt of the LG 300 is so much higher than the LG 275. The PTC rating of the LG 300 is 274.5 Watts. The M250 efficiency is 96.5%. If you multiply the two, the "potential" maximum AC power from each solar panel is 264.5 Watts. However the M250 inverter has a maximum output of just 250 Watts. I know the Enphase data sheet states the recommended DC input power is up to 300 Watts. Buy they also published a document admitting that clipping can occur, but not to worry, because it only happens part of the time. Think about a string inverter or solaredge with optimizers.

[AMCSquared]

LG 300's are currently in-stock in San Diego, no issue there. Keep in mind this configuration will result in "clipping", which is a shame because the cost per watt of the LG 300 is so much higher than the LG 275. The PTC rating of the LG 300 is 274.5 Watts. The M250 efficiency is 96.5%. If you multiply the two, the "potential" maximum AC power from each solar panel is 264.5 Watts. However the M250 inverter has a maximum output of just 250 Watts. I know the Enphase data sheet states the recommended DC input power is up to 300 Watts. Buy they also published a document admitting that clipping can occur, but not to worry, because it only happens part of the time. Think about a string inverter or solaredge with optimizers.

Thanks for the pointer. I have read their documentation (which is more about M215). According to their Table 5: Los Angles, 20 Degree (my roof is at 18 degree), and 285 Watt panel would have a 0.13% annual production loss due to clipping. Once again, this documentation is referring to the less powerful M215 and not the current M250.

If you read M250's specification, Enphase says M250 is good for 240W continuous and 250W peak. They also don't specify how long it can operate at 250W. They basically said that M250 will dial back the production to protect the unit when it get "too hot." However, 240W is rated if it operate within the designed environmental range. That said, we all know that solar panel looses its efficiency as it gets hotter also.

Another point, according to LG 300's spec, it can loose up to 3% on the first year usage (and then about 0.7% for the remainder of the 25 year production warranty). I think after one or two years and dirty panels, LG 300 probably would be producing closer to like a 285W panel. I have looked at PVWatt's hourly output using my location, orientation, tilt, and 0.84 derate. I have only seen a handful of time where the average AC production is over 250 watts (on a per panel basis in one hour block). I think PVWatts data does consider temperature as one of the variables. Of course 0.84 derate may or may not be realistic with the LG 300 + M250 combo.

You don't need an engineering degree to know it is probably not a good idea to run things at the theoretical limit. Also, I would never take a "marketing" study from the manufacturer at face value. I have not doubt there will be times when M250 will clip with LG300W in San Diego. The question becomes how often, how long (i.e. half an hour vs. couple hours), and how much loss. I would certainly not run SunPower 325W+ type of panel with the M250. However, I think Enphase is probably close to being right saying M250 shouldn't be used with anything above 300W.

[J.P.M.]

Thanks for the pointer. I have read their documentation (which is more about M215). According to their Table 5: Los Angles, 20 Degree (my roof is at 18 degree), and 285 Watt panel would have a 0.13% annual production loss due to clipping. Once again, this documentation is referring to the less powerful M215 and not the current M250.

If you read M250's specification, Enphase says M250 is good for 240W continuous and 250W peak. They also don't specify how long it can operate at 250W. They basically said that M250 will dial back the production to protect the unit when it get "too hot." However, 240W is rated if it operate within the designed environmental range. That said, we all know that solar panel looses its efficiency as it gets hotter also.

Another point, according to LG 300's spec, it can loose up to 3% on the first year usage (and then about 0.7% for the remainder of the 25 year production warranty). I think after one or two years and dirty panels, LG 300 probably would be producing closer to like a 285W panel. I have looked at PVWatt's hourly output using my location, orientation, tilt, and 0.84 derate. I have only seen a handful of time where the average AC production is over 250 watts (on a per panel basis in one hour block). I think PVWatts data does consider temperature as one of the variables. Of course 0.84 derate may or may not be realistic with the LG 300 + M250 combo.

You don't need an engineering degree to know it is probably not a good idea to run things at the theoretical limit. Also, I would never take a "marketing" study from the manufacturer at face value. I have not doubt there will be times when M250 will clip with LG300W in San Diego. The question becomes how often, how long (i.e. half an hour vs. couple hours), and how much loss. I would certainly not run SunPower 325W+ type of panel with the M250. However, I think Enphase is probably close to being right saying M250 shouldn't be used with anything above 300W.

Are you coastal, inland, mountain or desert ? Closer to Miramar or downtown ? Depending on how much I believe Enphase, I can SWAG clipping hrs. and yearly total kWhrs clipped for no shade scenario using some stuff I wrote. SAM will do the same, but takes a bit of finesse. Holler back w/ confirmed elevations & azimuths or PM if interested.

[peni007]

Hi AMCSquared

I am in a similar situation (living near coast in SD) and looking at a system between 3-4 kW. I know we cannot divulge an installer's name but is company "S" have another S and P in its name?

Thanks!

[J.P.M.]

Hi AMCSquared

I am in a similar situation (living near coast in SD) and looking at a system between 3-4 kW. I know we cannot divulge an installer's name but is company "S" have another S and P in its name?

Thanks!

FWIW, my guess is they're a Gaelic outfit.

[AMCSquared]

Are you coastal, inland, mountain or desert ? Closer to Miramar or downtown ? Depending on how much I believe Enphase, I can SWAG clipping hrs. and yearly total kWhrs clipped for no shade scenario using some stuff I wrote. SAM will do the same, but takes a bit of finesse. Holler back w/ confirmed elevations & azimuths or PM if interested.

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.

[AMCSquared]

Hi AMCSquared

I am in a similar situation (living near coast in SD) and looking at a system between 3-4 kW. I know we cannot divulge an installer's name but is company "S" have another S and P in its name?

Thanks!

Just do a search for "San Diego Solar" on Google. The company does show up in the 1st page (non-paid). I won't be anymore specific in order to not run afoul of the rules. All I can say is that there are only so many Company "S". Please PM me if you want specific.

[HX_Guy]

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

[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.

[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.]

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.

[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.