San Diego DIY install

[wiedhas]

I have received some crazy quotes for a system at my house. One was 10KW (sunrun) for $45k and the other was for 12KW for $42k(400W Panasonic panels, enphase micro inverters). I want to get the NEM 2.0 agreement and install myself (with help). I have an EV as well as 3 heat pumps + a pool heat pump all being installed this year so I will not really know my power needs exactly. I have been running avg 37KW per day according to my bill so a 10KW system or greater is best. PVWATT says a 12KW system will produce ~20,000KWH a year at my location. My roof has good southern exposure with room for a 10KW system and a huge amount of west facing area for spillover. Couple of questions:

1. I am planning on using Enphase Energy IQ8 IQ8M-72-2-US micro inverters. But since I have no shade problems (except for marine layer!) should I use these?
2. The application to SDGE requires a specific panel model number and I need to submit this application ASAP. I have narrowed the panels down to Q.PEAK DUO BLK ML-G10+ 400 and Panasonic EVPV400HK. Are these good choices? Any other panels that would be better?
3. Although not necessary, I would like to have an AC disconnect switch. Will a 60amp switch work for a 12KW setup? Would a Siemens HNF362PV 60 A, 600V AC/DC, 3 pole, NEMA 1 be a good choice?

I am looking forward to this project and can def spend the money saved on install elsewhere. Any help appreciated.


Thanks for reading

[SunEagle]

Welcome to Solar Panel Talk.

All I can say is that performing a DIY install may require you to jump through some legal hoops to satisfy the AHJ and POCO. Some members have done it and saved money others ran into issues with the legal process and hardware failures. I hope you can do the work and get your system installed.

[J.P.M.]

If it was me, after I disabused myself of the folly of working with Sunrun and the other bottom feeders, I'd get a better or at least some estimate of what your expected total annual usage will be before I worried about which panel to buy. I would SWAG about 3 miles/kWh as an EV electrical budget.

Your PVWatts model's output is a long-term average. The most likely outcome will be maybe +/- 10% of that number over any 365 day period. I'm in 92026 with close to optimum orientation with ~ 3.5 % annual shade and my 10+ year old system produces ~ 1,736 kWh/running 365 day period per installed STC kW, +5.4/-4.6 % over that 10+ yr. period. Annual system output degradation is ~ 0.35% to ~ 0.40% or so and seems pretty linear with respect to time.

As for your choice of panels, know that beyond some basic quality level, panels are pretty much a commodity. All decent quality panels are all pretty reliable and all about equal in terms of annual output per installed STC W. Just don't buy rock bottom quality.
Also, if you have no shade problems, do yourself a big favor (IMO) for a lot of reasons and skip the equalizers for a straight string inverter setup. Less complicated == less to go wrong, KISS rules. The pages on the site are littered with horror stories about optimizers and micro inverters compared to problems posted about string inverters. Take a look and see what i'm writing about.

Some others here are better qualified to comment on your 3d question.

I'd add that those system prices you write of seem high, especially for a DIY job, even after all the price gouging going on as a result of the 04/13/2023.

Welcome to the neighborhood.

[Mike 134]

Roof mount forces you to have "something" on the roof to meet codes to shut down the panel output at the panels on a sunny day. Whether that's optimizers, micro inverters, or some other makers gizmo your stuck.

[J.P.M.]

Roof mount forces you to have "something" on the roof to meet codes to shut down the panel output at the panels on a sunny day. Whether that's optimizers, micro inverters, or some other makers gizmo your stuck.

Like something from Tigo or Sunspec for string inverters maybe ?
I think I understand and at least 100% support the basics and intent of NEC 690.12 for rapid disconnect requirements but why would panels need to be shut down solely because it's a sunny day?

[Mike 134]

Like something from Tigo or Sunspec for string inverters maybe ?
I think I understand and at least 100% support the basics and intent of NEC 690.12 for rapid disconnect requirements but why would panels need to be shut down solely because it's a sunny day?

Didn't say shutdown "solely" for a sunny day you injected that idea. and yes something like Tigo offers for shutdown.

[J.P.M.]

Didn't say shutdown "solely" for a sunny day you injected that idea. and yes something like Tigo offers for shutdown.

If by inject you mean infer something into your statement, as a matter of respect for others I take folks at their word and try very hard not to infer anything. I have a hard time getting a clear meaning of what you're writing from the way you write. Please excuse my ignorance.

Sometimes I read/hear things that I interpret as incorrect or that confuse me or seem unclear to me.
That's why I ask questions as I did of your post.

I also wondered that since power, voltage and (some) current can be generated by an operating PV system under overcast skies as well as sunny skies, why your statement that I questioned seems, to me anyway, to limit the need for rapid shutdown to only under sunny skies, but I don't want to give the impression of trying to seem pedantic.

The last word is yours if you want it.

[wiedhas]

Thanks for the replies. Took a deep(ish) dive into micro inverters vs string. Panel tech is great at dealing with shadows which I won’t really have. Several questions arise.

It’s the south and west string direction that poses a prob. Would a string inverter be able to handle two differently mounted panels?

With enphase units having such a small failure rate is it really money saving when the avg life of a string inverter is 10 years?

And if I went with the string inverter, would I have to put a disconnect switch on the roof? And would a string inverter hinder adding a battery in the future?

thanks

[jflorey2]

It’s the south and west string direction that poses a prob. Would a string inverter be able to handle two differently mounted panels?

Generally wise to put the two strings on different MPPT inputs. Most grid tie inverters have more than one MPPT these days.

With enphase units having such a small failure rate is it really money saving when the avg life of a string inverter is 10 years?

Yes.

A LOT easier to service a string inverter.

And if I went with the string inverter, would I have to put a disconnect switch on the roof?

Not on the roof, no. Near your electrical panel.

And would a string inverter hinder adding a battery in the future?

String inverter makes it easier than microinverters. You have more options.

[Mike 134]

If by inject you mean infer something into your statement, as a matter of respect for others I take folks at their word and try very hard not to infer anything. I have a hard time getting a clear meaning of what you're writing from the way you write. Please excuse my ignorance.

Sometimes I read/hear things that I interpret as incorrect or that confuse me or seem unclear to me.
That's why I ask questions as I did of your post.

I also wondered that since power, voltage and (some) current can be generated by an operating PV system under overcast skies as well as sunny skies, why your statement that I questioned seems, to me anyway, to limit the need for rapid shutdown to only under sunny skies, but I don't want to give the impression of trying to seem pedantic.

The last word is yours if you want it.

My view of "debates" on the internet are they are no different than "debates" with drunks in bars.

[wiedhas]

Thanks for the reply. So I am inclined to go the string inverter route and want somewhere between a 10-12KW system. Don't think I need half cut panels unless you all think otherwise. I've read good things about Froinius inverters but they are hard to get into the US? Can anyone recommend a good inverter that can handle the above system? For 10KW - 8KW inverter would work?

Thanks

[J.P.M.]

Thanks for the reply. So I am inclined to go the string inverter route and want somewhere between a 10-12KW system. Don't think I need half cut panels unless you all think otherwise. I've read good things about Froinius inverters but they are hard to get into the US? Can anyone recommend a good inverter that can handle the above system? For 10KW - 8KW inverter would work?

Thanks

Around here (San Diego county), the max. power out of an inverter for an optimally oriented array (azimuth ~ 210 degrees, tilt ~ 30 degrees) under cloudless skies will probably occur around this time of year and will be about 85% to maybe close to 90% of the array's STC rating.
Other, off optimum orientations such as you are thinking about will have lower maximum outputs.
All that said, a DC to AC ratio of > maybe 1/0.85 = 1.18 ~ 1.2 or so will keep you out of clipping. A higher ratio won't get you much.
FWIW my string inverter is 5 kW and my array is 5.232 kW and pretty much optimally oriented.
The max. instantaneous output ever achieved by my array under clear skies was 4.833 kW into the inverter and 4.689 kW out of the inverter.

If I was designing another array today, I'd go with SMA for inverters.

Edit:
Forgot to add/distinguish that optimum orientation is to maximize the value of generated electricity for schedule DR-SES T.O.U. generated electricity.
Optimum orientation to maximize generation per installed STC kW around most of San Diego county is about 195 azimuth and that same 30 degree tilt.
Apologies for the lack of clarity.

J.P.M.

[wiedhas]

Thanks for the info. I’ll report back here with system details when I submit my application.

anyone know of a good place to purchase diy systems? Renvu.com?

[fraser]

Thanks for the info. I’ll report back here with system details when I submit my application.

anyone know of a good place to purchase diy systems? Renvu.com?

I am in process of buying some pieces from Renvu.com. Unfortunately I have a flat roof, so they don't sell good racking components for that. So that has extended my process. If you can put the panels on an existing southerly tilted roof, then that is perfect. I've done way too much research but this will help:

1) You might as well hire the electrician to do the electric work, you aren't going to be able to do it anyway. I personally would hire an existing crew from Craigslist or ask the electrician. Use good flashing feet for the roof penetrations and you should be fine.
2) Larger panels with optimizers and a growatt 11.4 or 10.0 string inverter will keep your costs down. Panels need to be under $.60/watt. Renvu has several. AcoSolar has them too. You can contact bluesun directly too, they have all black ones in a CA warehouse that are about that price too. I would overbuild if you have the roof space since you can get it all into NEM 2.0 then. And you will use it. Don't worry about the excess generation. I just ran the numbers to check: $11,800 delivered including racking et all for 10.8kw. Mine is about $13.8k for a 16kw system, including 2 inverters, but I have to get the racking elsewhere (about $2k) and add ~$2-3k for the panel upgrade. Still have to pay the installers and the electrician too. I expect to pay a total of about $25-27k for the 16kw system including the new electric panel. I considered going for a smaller 12.96 kw system, since I would need only 1 inverter. That would be optimal in my opinion as it is $13.1k total including racking and tax (not shipping).
3) Do not worry about having the panels perfectly south. As long as the roof isn't pointing north, you will have minimal losses with a subobtimal azimuth. You might lose 3-6% on a system pointed 20 degrees off of dead south (160-200degree azimuth), so put the panels where you can.
4) Check your electric panel and make sure you either have a solar ready panel or you will have to either replace it, degrade your breaker, or do a line side tap. The 10.0 kw inverter has a max output of 42amps, so you need to have room for that. I got caught by that and had to replace the elec panel.
5) Make sure you have all the parts for your permit, then you can submit your interconnect agreement before you finish installing.
6) I'm using WattMonk for the permit drawings and stamps. I did not have good luck Illuminei (recommended by Renvu) as they didn't know how to do flat roofs properly. It's about $800 for this with the structural and elec stamps. You can try Unirac's Ubuilder software to get preliminary reports.

[wiedhas]

Thanks for the detailed reply Fraser.

1. I'm def going to hire out the work.

2,3. I'm leaning towards 1 12KW system but this means adding panels to a 300 azimuth facing roof. Otherwise 200 azimuth for a 10KW system

4.I have a 400 amp main panel (two 200 amp breakers) so I should be good since I have 80 amps of available power besides the grid?

The SDGE instructions don't call for any detailed plans if I'm going with a single line diagram system that they include so I won't need plans to get the agreement in. However they do ask for a SCIR - short circuit interrupt rating for systems larger than 10KW. Apparently this is printed somewhere on my main panel but I can't seem to find it. There was a sticker on the inside door of the panel but it is no longer there.


thanks