About to install LG300A1C-B3 300W AC microinverters, got some Q's

[AaronG]

They started installing today. The roof is prepped with the posts. The rails go down tomorrow and probably panels too. The inverter install tomorrow, but the AC disconnect was done today. New service panel last week...

So the stack of panels I got looks to be newer models than when I ordered. Cool. They are LG305N1C-B3. Initially I was going for LG300N1C-B3.
More to come. I'm excited though
lg.jpg

[J.P.M.]

Yes, the rates I'm pulling through SAM include the DWR charge, and match what is shown as the total rate in the Schedule DR effective 8/1/14. There are two entries listed for each of the climate zones to choose from though, but only the first one is correct.

Days per billing period variation definitely sets a ceiling to SAM's ultimate accuracy, and so I've typically been just averaging the days per generation season and using that to set the level of tiers for summer and winter. Not perfect, but it has agreed reasonably well with some of the other numbers you've shared. It supports 12 rate periods, so for a motivated user, each month could be tweaked to have an appropriate number of billing days. It doesn't solve the problem of the number of days changing from one year to the next, but would probably be more accurate than just the seasonal averages.

Also, the 0.17 / day min charge needs to be manually set as a $5.17 minimum monthly charge. Again, an approximation, but close enough for what I've been doing with it. Mostly, I've been relying on SAM for hardware specific energy production estimates that should be slightly improved over PVWatts, and doing the cost estimation work in a spreadsheet. Testing assumption sensitivity in SAM is kind of a pain with either re-simulating or running "parametrics", which itself has some UI quirks, while a spreadsheet can handle it more cleanly, once validated.

Understood. Sounds like the 2 entries may be for "standard" or "all electric" service - two more conditions in tiered rates that determine daily allowance that sets the baseline tier size which sets the other tier sizes. Glad the SAM rate sit. seems to have improved some. If the entries are for the purposes I describe, both entries for each climate zone are correct, but only one is applicable. See P.U.C. Sheet #24222-E, Sheet 5. I'm "all electric w/generally higher winter daily allowances and thus a bit lower annual bill than someone with "standard" (elec. and gas) service. On the old(er) SAM, I sort of patched the variable # of rate days by messing with the rates some (and corrected them at the same time), and using a rate schedule as close to the 1st of the month as possible for the general case in S.D., and billing cycle 3 from 2009 for my use. Didn't completely solve the problem, but helps some perhaps, keeping in mind it's all an estimate anyway.

I've done some stuff with the parametric anal. and agree it's kind of cranky. Hopefully, it's improved. I'll be using it again soon and get back up to speed on it for the fouling data I've been conjuring up since last spring.

[sensij]

Do they have the DWR bond charge and misc. taxes in them yet ? Missing before. Also, one of the bigger problems w/ SAM's rate structure, besides inaccurate or completely missing energy charge portion was the 20 different billing schedules SDG & E uses with varying # of days/billing period (29 to 32) that rarely conformed to or start on a calendar month and that changed every year on top of that.

Yes, the rates I'm pulling through SAM include the DWR charge, and match what is shown as the total rate in the Schedule DR effective 8/1/14. There are two entries listed for each of the climate zones to choose from though, but only the first one is correct.

Days per billing period variation definitely sets a ceiling to SAM's ultimate accuracy, and so I've typically been just averaging the days per generation season and using that to set the level of tiers for summer and winter. Not perfect, but it has agreed reasonably well with some of the other numbers you've shared. It supports 12 rate periods, so for a motivated user, each month could be tweaked to have an appropriate number of billing days. It doesn't solve the problem of the number of days changing from one year to the next, but would probably be more accurate than just the seasonal averages.

Also, the 0.17 / day min charge needs to be manually set as a $5.17 minimum monthly charge. Again, an approximation, but close enough for what I've been doing with it. Mostly, I've been relying on SAM for hardware specific energy production estimates that should be slightly improved over PVWatts, and doing the cost estimation work in a spreadsheet. Testing assumption sensitivity in SAM is kind of a pain with either re-simulating or running "parametrics", which itself has some UI quirks, while a spreadsheet can handle it more cleanly, once validated.

[J.P.M.]

In the new beta version, the biggest problem with the SDG&E imported rates is that the Baseline and Tier values are based on kWh per day, when all of SAM's calculations are done based on monthly usages. The tiers need to be scaled to an average monthly level for winter and summer to get results that make sense. The actual $ / kWh are reasonably accurate.

There are a few other bugs... fields that should accept decimal numbers that don't, and some of the automated sizing routines seem flaky. Actual calculations have appeared solid so far.

Do they have the DWR bond charge and misc. taxes in them yet ? Missing before. Also, one of the bigger problems w/ SAM's rate structure, besides inaccurate or completely missing energy charge portion was the 20 different billing schedules SDG & E uses with varying # of days/billing period (29 to 32) that rarely conformed to or start on a calendar month and that changed every year on top of that.

[sensij]

Be careful on SAM's SDG & E rates. I haven't checked the newest SAM rev's but the rates on the prior rev. were WAY off. I'd bet if correct are still an approx. due to complications of SDG & E rate fine points. Maybe they've been fixed. I've been using SAM for several years and will download the BETA version once I'm convinced the bugs/crap are puked out. Great tool, but it does strange things at times.

In the new beta version, the biggest problem with the SDG&E imported rates is that the Baseline and Tier values are based on kWh per day, when all of SAM's calculations are done based on monthly usages. The tiers need to be scaled to an average monthly level for winter and summer to get results that make sense. The actual $ / kWh are reasonably accurate.

There are a few other bugs... fields that should accept decimal numbers that don't, and some of the automated sizing routines seem flaky. Actual calculations have appeared solid so far.

[J.P.M.]

Good point, Miramar would be a better test. That would bump it up to 12267 kWh output, with 9 hours of clipping. One interpretation is that more sun in Miramar brings the overall output up, but warmer temps cut down slightly on the peak power hours.

Agreed. BTW, on temps. - one thing I've known as a blinding flash of the obvious, but more firm in my mind as a result of all the panel fouling measurements I'm doing is that my air roof temps at min. incidence angle on the array and probably to a lesser degree all day are about 8 to 12 deg. F warmer than the ground ambient or "porch" temp. That's good for my roof only, but I'd suggest it's likely for a lot of other locations as well, at least to some degree. .

[J.P.M.]

That is a really cool tool. I plugged in my area, set the tilt, azimuth, and got sdge rates, etc. and then ran some simulations. very neat. There are so many dang metrics though. I dont think I'll put in the time to try to master this tool, but I can see how valuable it could be. It'd be neat to see someone who knew this thing perfectly run through some scenarios with me. oh well, no biggy. Still, neat tool. Thanks... Up until now I only knew about PVWatts.

Be careful on SAM's SDG & E rates. I haven't checked the newest SAM rev's but the rates on the prior rev. were WAY off. I'd bet if correct they are still an approx. due to complications of SDG & E rate fine points. Maybe they've been fixed. I've been using SAM for several years and will download the BETA version once I'm convinced the bugs/crap are puked out. Great tool, but it does strange things at times.

[AaronG]

Yes, exactly. The simulation conditions are with a bigger system in better sunshine and with better panel orientation. So to the extent that a simulation run by a random person on the internet can be trusted, your system will have even less clipping. SAM is free if you'd like to run your own simulations, although some concurrent time with the documentation might be well spent.

That is a really cool tool. I plugged in my area, set the tilt, azimuth, and got sdge rates, etc. and then ran some simulations. very neat. There are so many dang metrics though. I dont think I'll put in the time to try to master this tool, but I can see how valuable it could be. It'd be neat to see someone who knew this thing perfectly run through some scenarios with me. oh well, no biggy. Still, neat tool. Thanks... Up until now I only knew about PVWatts.

[sensij]

I thought the orientation was WSW ? Also, Miramar (preferable) or Carlsbad airport may be more rep. than San Diego, FWIW.

Good point, Miramar would be a better test. That would bump it up to 12267 kWh output, with 9 hours of clipping. One interpretation is that more sun in Miramar brings the overall output up, but warmer temps cut down slightly on the peak power hours.

[sensij]

Wow thats great info you shared, thank you. really thanks a ton! very cool
Isn't 180 direct south like the most ideal. So you technically will see better yields than I could possibly at my azimuth.
Here's a pic of my plan submitted.
[ATTACH=CONFIG]5009[/ATTACH]

Yes, exactly. The simulation conditions are with a bigger system in better sunshine and with better panel orientation. So to the extent that a simulation run by a random person on the internet can be trusted, your system will have even less clipping. SAM is free if you'd like to run your own simulations, although some concurrent time with the documentation might be well spent.

[J.P.M.]

The SE7000 is a real product, but only puts out 6000W at 240 V. It isn't clear what the extra $100 would be buying here.

FWIW, a quick run of 22 -G3 panels using SAM defaults (20° tilt, 180 azimuth, san diego TMY2) yields 11841 kWh annually using the SE7600A, and 11826 kWh using the SE6000. The hourly chart shows a few days with clipping in April and May, but for only around an hour at the peak of the day, 14 hours total in the year. -B3's aren't in the database yet, and I can't figure out how to make one string of 10 and the other of 11, so please just consider these numbers illustrative. Depending on the details of the actual installation, the results will be different, but really, there is nothing wrong with the SE6000 in this case.

I thought the orientation was WSW ? Also, Miramar (preferable) or Carlsbad airport may be more rep. than San Diego, FWIW.

[AaronG]

The SE7000 is a real product, but only puts out 6000W at 240 V. It isn't clear what the extra $100 would be buying here.

FWIW, a quick run of 22 -G3 panels using SAM defaults (20° tilt, 180 azimuth, san diego TMY2) yields 11841 kWh annually using the SE7600A, and 11826 kWh using the SE6000. The hourly chart shows a few days with clipping in April and May, but for only around an hour at the peak of the day, 14 hours total in the year. -B3's aren't in the database yet, and I can't figure out to make one string of 10 and the other of 11, so please just consider these numbers illustrative. Depending on the details of the actual installation, the results will be different, but really, there is nothing wrong with the SE6000 in this case.

Wow thats great info you shared, thank you. really thanks a ton! very cool
Isn't 180 direct south like the most ideal. So you technically will see better yields than I could possibly at my azimuth.
Here's a pic of my plan submitted.
solar.jpg

[sensij]

The SE7000 is a real product, but only puts out 6000W at 240 V. It isn't clear what the extra $100 would be buying here.

FWIW, a quick run of 22 -G3 panels using SAM defaults (20° tilt, 180 azimuth, san diego TMY2) yields 11841 kWh annually using the SE7600A, and 11826 kWh using the SE6000. The hourly chart shows a few days with clipping in April and May, but for only around an hour at the peak of the day, 14 hours total in the year. -B3's aren't in the database yet, and I can't figure out how to make one string of 10 and the other of 11, so please just consider these numbers illustrative. Depending on the details of the actual installation, the results will be different, but really, there is nothing wrong with the SE6000 in this case.

[thejq]

I'm sure you'll be fine with SE6000. I just thought for $100 more, why not. But if you can't find SE7000, there's no point spending $700 extra for SE7600. FWIW, I like to run things under its rating.

[sensij]

As others have said, whatever clipping you will see will add up to very little. Also, keep in mind that the 6300 W is year 0 power. These panels will break in a % or two in the first year, then drop maybe 0.5% annually after that. Even if they are high on the power tolerance (+ 3%), whatever miniscule amount of clipping occurs will be less every year, and should be gone by year 10 or sooner.