Proposed solar array install

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Mr. Kelly

Feeling the Heat
Hi everyone,

I am new to the solar world, and I am researching what two different solar companies locally have offered… I’d like to know your input on it, since I’m not hugely well-versed with solar technology. Sorry if this is redundant… or mundane…

here is what I have been quoted:

Company #1:

● Panel: Q.Cells, 25-year power production = 5500 W
warranty, 25-year material warranty
● Inverter: SMA 10-year material and power production warranty

● 10 year installation warranty

Total system cost: $16,500 (not including federal/state tax incentives)
I am going to finance a 10 year loan… Their solar loan is 4.99%


Company #2:

16 panels: Longi 355 BOB= 5700 W
25 year production warranty
● Inverter: Enphase Micro inverters per panel
25 year production warranty

15 year installation warranty

Total system cost: $23,500

Their solar loan for 10 years is .99%

So, I am doing an A/B analysis between the two offerings…

First things first… What do you think about the difference between the two different manufacturers of panels? Anybody have any background with these companies?

Next… One company offers an inclusive single inverter, while the other company is touting a single microinverter per panel, citing if one microinverter goes down, the whole system still remains active.

Does anybody have any input regarding going with either a single inverter versus micro inverters?

The financial part of it I will have to work out myself and figure out the costs and details. My initial calculations says that the difference in loans is really only about $500 over the length of the loan, which does not bridge the gap between the difference in total price of the system. So that is somewhat of a wash.

On the surface, company one offers a cheaper solution, but with less warrantee and perhaps more liability with the inverter. The alternate company is a good chunk more for the system price, but may balance it off with better overall warrantees and less liability with the microinverters?

Is there anything that I am not seeing, or any input that you can provide that might make a choice like this a little less confusing?

Thanks for any and all help you can give!
 

ABMax24

Minister of Fire
Sep 18, 2019
1,229
Grande Prairie, Alberta, Canada
Get a third quote, personally I believe both of those are on the high end of what they should be. My 3kw micro inverter setup cost me $3.06/watt all in 2.5 years ago, those quotes are $3/watt and $4.12/watt.

I'm running micro inverters on my house, because my arrays are too small to be used on a string inverter. If your array experiences shading micro-inverters are a better option as only the shaded panels see a reduction in output. If you won't experience issues with shading a string inverter will work just fine.

If you are interested in micro-inverters see if there is an installer that works with APSystems, I have their YC600 inverters and they have worked well so far and are much more cost effective than the Enphase units. The new QS1 inverters should be more cost effective yet as they run 4 panels per inverter. The benefit of the APSystem inverters is each panel still has its own MPPT circuit, allowing each panel to see shading without effecting output of the others.
 

stoveliker

Minister of Fire
Nov 17, 2019
2,049
Long Island NY
Microinverters indeed, note that that even holds for no trees but a chimney... Or if you have big birds that poop...

Look at what the material warranty is; it should be specified as a decrease in performance per year.

I don't know the second set of panels, but I got my (LG) panels and (Enphase) microinverters at 7.2 kW for $22k. Your quotes seem too expensive.

Also, you don't have to get a loan from the installer. I got a loan from my bank and paid the installer upon install. So shop around for loans.
 
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Solarguy3500

Member
Dec 3, 2020
194
Western MA
Both of those panels are what we call Tier 1 commodity level standard efficiency panels, which generally have a 10 or 12 year workmanship warranty. The quote at over $4.00/watt definitely seems high, and the other one might be too. I usually quote LG panels which are high efficiency panels with a 25 year workmanship warranty and 25 year power production guarantee in the low $3.00/watt range or lower, depending on installation complexity.

There is definitely truth to the idea of microinverters not having a "single point of failure" and I have been quoting them a lot lately. Another thing about the SMA string inverter is that in addition to shading impacting production (each panel on a string of panels will output the power of the lowest performing panel on the string) if you have multiple arays on different roof surfaces with different orientations and tilt angles, this will also negatively impact production.

If you want, you can send me a DM and I can quote it up for you so you know where the price should be. I have recently caught other companies trying to overcharge people significantly, so it's possible that could be going on here. If you want to check out the company I work for, look up SunBug Solar. We have two offices, one in Eastern MA and the one in Western MA that I work from in Westfield.

As far as the loans go, I would recommend checking out the UMass Five College Credit Union. They have a solar loan program they developed called MySolar that is a good choice. Also, the Clean Energy Credit Union has good loan options for all kinds of energy efficiency and clean energy projects including solar.
 

BCC_Burner

Feeling the Heat
Sep 10, 2013
452
Uptown Marble, CO
Paying 5% interest on any kind of loan with rates where they are today should be a non-starter right there. I would have laughed in the guys face when he told me the terms of that loan.
 

peakbagger

Minister of Fire
Jul 11, 2008
6,635
Northern NH
I agree the prices seem steep.

Do you have any potential shading issues on your roof?. If there are any shadows either vertical or horizontal that could cover one or more panels, microinverters deal with shadows slightly better. The trade off is complexity of the electronics on the roof under the panels. The SMA package is a central string inverter that can be located in nice cool shady place like a basement. There are electric "boxes" at each panel for rapid shutdown and shading protection but the electronic components at each panel are in theory relatively robust. On the other hand any panel mounted microinverter is far more complex. There is a higher potential failure rate up on the roof and more of them to fail over the life of the system. So if you have no shadows I recommend sticking with the simpler potentially more robust SMA string inverter.
 

peakbagger

Minister of Fire
Jul 11, 2008
6,635
Northern NH
BTW, if the proposal does not include a high quality surge suppressor on the circuit that ties the PV system to the main panel make sure one is added to the proposal. A whole house suppressor is not as good as a dedicated one on the PV circuit but many folks who want a whole house throw it in with the PV system so they can get the rebate. The brand that has the best rep is Midnight Solar SPD.
 

Mr. Kelly

Feeling the Heat
Hi again all…

Thank you, I am ecstatic with your responses. Lots to consider!

Here’s a bit of a curveball… Is there any sense in the thought of buying all the products myself and hiring an installer to put it up there? I suspect I lose warrantee considerations, which is likely the biggest prohibitive?
 

peakbagger

Minister of Fire
Jul 11, 2008
6,635
Northern NH
Folks like myself do self installs. I have done 3 arrays and a major reconstruction of one of them. I designed them and installed them so I get to make it work. Few contractors will install owner bought equipment as they do not want to be responsible for equipment warrantees. They also can make profits off the equipment and materials as well as the labor so its less profitable job. I might pay a bit more for my equipment that a contractor but my "free" labor offsets that cost significantly. It takes me bit longer but I dont take shortcuts and am not worries about hidden short cuts.

Most solar installs are pretty well "plug and play", The biggest PITA is permitting as local inspectors tend to want it done their way and have trained the local contractors to supply them what they want. Most are busy so they rarely want to take the time to educate a home owner to DIY. That said there are firms sell "kits" that can be inclusive. Its not a bad exercise to design a system on paper and see what you are paying for premium. Its with picking up a copy of Solar Power your Home for Dummies. Even if you do not plan to do an install it educates you on the process.

One additional major PITA is setting up communications to the inverter. Most systems can be be run standalone but the manufacturers really want you to connect online. Most of the issues I see is this remote setup, contractors set it up when they do the install and when its acts up they disappear leaving the homeowner to figure it out. If you are selling SRECS you probably are stuck with communications but if not you may be able to skip it albeit with some lose of functionality. All three of my systems are dumb, they just sit there and run with no communications. I sell SRECs but i report my numbers manually every month by email.

Folks on this forum, including myself have talked a few folks through the design process in the past.
 

ABMax24

Minister of Fire
Sep 18, 2019
1,229
Grande Prairie, Alberta, Canada
Hi again all…

Thank you, I am ecstatic with your responses. Lots to consider!

Here’s a bit of a curveball… Is there any sense in the thought of buying all the products myself and hiring an installer to put it up there? I suspect I lose warrantee considerations, which is likely the biggest prohibitive?

I'm assuming you are considering this to save cost, which I don't believe you will. Many installers hide some of their costs on the markup of the product, remove that from the equation and the labor portion increases. So with that being said I think in the long run it would cost you more, because the installer can get components cheaper because of the volumes they sell.
 

peakbagger

Minister of Fire
Jul 11, 2008
6,635
Northern NH
I beg to disagree, there are many direct to public firms like Alt E stores that sell direct to public. Yes a large contractor gets some volume discount but the direct firms get pretty close. Labor is the expensive part. If I don't count my labor my arrays all were far less costly than a contractor could install one for. On the other hand if I charged my former field service rate of $150 an hour plus a 15% markup on top of expenses no doubt a solar contractor would beat my cost. I happen to have DIY mindset where I quickly forget the grunt work and enjoy being able to say I installed it my self. Other folks would rather have a beer and go fishing. I expect its the way I was brought up. The guy I used to work for despite being a great engineer would not even consider DIY as he thought it was beneath him. I cut my wood and burn it, he wrote a check to the gas company.

One big caveat is the big solar firms get very creative with accounting and they can hide things like incentives, creative long term depreciation and ongoing revenue like SRECs and battery dispatch into their deal. Some one who does not take the time to understand the contract will most likely end up with lease or PPA with low monthly payment but odds are they will regret it in the long run.
 

ABMax24

Minister of Fire
Sep 18, 2019
1,229
Grande Prairie, Alberta, Canada
I beg to disagree, there are many direct to public firms like Alt E stores that sell direct to public. Yes a large contractor gets some volume discount but the direct firms get pretty close. Labor is the expensive part. If I don't count my labor my arrays all were far less costly than a contractor could install one for. On the other hand if I charged my former field service rate of $150 an hour plus a 15% markup on top of expenses no doubt a solar contractor would beat my cost. I happen to have DIY mindset where I quickly forget the grunt work and enjoy being able to say I installed it my self. Other folks would rather have a beer and go fishing. I expect its the way I was brought up. The guy I used to work for despite being a great engineer would not even consider DIY as he thought it was beneath him. I cut my wood and burn it, he wrote a check to the gas company.

One big caveat is the big solar firms get very creative with accounting and they can hide things like incentives, creative long term depreciation and ongoing revenue like SRECs and battery dispatch into their deal. Some one who does not take the time to understand the contract will most likely end up with lease or PPA with low monthly payment but odds are they will regret it in the long run.

I'm not arguing that a self-install isn't cheaper, because it would be. My post was stating that the OP won't save money suppling the materials to the installer.

Another item to consider is if the municipality allows DIY installs, my city does not, so as much as I would have liked to install it myself I was forced to pay someone to do the work.
 

peakbagger

Minister of Fire
Jul 11, 2008
6,635
Northern NH
Okay sorry I misunderstood.

I agree it depends on the location if a self install is acceptable. For my last install I needed and electrician to sign off so I could sell SRECS. He didnt know solar so I showed him how to design and install to the code including referencing the applicable code sections. He signed off without getting out his truck.
 

semipro

Minister of Fire
Jan 12, 2009
4,084
SW Virginia
One additional major PITA is setting up communications to the inverter. Most systems can be be run standalone but the manufacturers really want you to connect online. Most of the issues I see is this remote setup, contractors set it up when they do the install and when its acts up they disappear leaving the homeowner to figure it out.
I would consider this to be a major selection criterium for a new system. Depending upon the Internet to monitor the status of your system can be a major inconvenience, especially if you use your system for backup during grid outages. Your modem and router may be cranking away on backup but if the backhaul fiber/cable/copper and supporting equipment are down it's useless.
 

Solarguy3500

Member
Dec 3, 2020
194
Western MA
I think where @Mr. Kelly would run into trouble with a DIY solar installation is that in MA where he lives the law is that you have to have 1 licensed electrician for every unlicensed apprentice to install solar. Electrical inspectors can be pretty brutal if they catch you out of ratio. If you hire a regular electrician to do the install, they might not be familiar with the specifics of solar installation, as @peakbagger alluded to in his post.

There is also the utility interconnection process which could be difficult to navigate for someone who is not familiar with it, and the permitting process with the local building and electrical departments who are going to want to see plansets, electrical diagrams, structural engineer's report, etc.

Also, the process of applying for the incentive programs like the SMART program or Class 1 RECs would be confusing if you haven't done it before.
 

Mr. Kelly

Feeling the Heat
Hi again,

i’m continuing to research the difference between micro inverters and a single inverter… And one of my resources said this…

“Micro inverters won't increase your system's performance. Each panel will produce independently of the others regardless of which type of inverter you use. It is no longer true (and hasn't been for years) that you need micro inverters for maximum system production.

Enphase also only has a 2 year labor warranty so any repairs end up being costly since it would involve roof work. The inverter is the most likely piece of equipment to fail on any system since it is doing the majority of the work.”

thoughts?
 

peakbagger

Minister of Fire
Jul 11, 2008
6,635
Northern NH
I will start with the recomendation that the best investment is buy a copy of Solar Power your Home for Dummies. You will get an education that you will not get asking random questions.

So to answer the questions we need to know if this is going on the roof a house (or dwelling unit) or a ground or pole mount. Non occupied buildings like garages are a gray area up to the AHJ. If its a roof mount in most states you need Rapid Shutdown Devices (RSD) to automatically kill the power within 1 foot of the junction box on the solar panels. Ground and pole mounts do not need RSD. Thus you need a String Inverter with module level devices to implement RSD or microinverters at each module. If you have a pole or ground mount you dont need RSD so you save money offset by more expensive mounts. Inverters are complex electronics that are converting DC to AC along with Multiple Power Point Tracking (MPPT) circuitry. Solar panels vary in voltage and current as the sunlight varies so the MPPT is constantly tweaking the voltage to see if the current increases. Power is voltage times current so the MPPT is always trying to maximize the total power from the panel. In the case of a microinverter the MPPT is tuning the individual panels so the overall power output can be higher if some panels have different levels of sunlight over the course of the day.

A string inverter with RSD on a house roof will need a device at each panel to turn the power off to the wiring at the panels in case of emergency or loss of grid. These devices are far less complex than a microinverter. I think they are basically a panel powered "brain" on a chip. They are usually called an optimizer. They also minimize the impact of partial shading on the panel to the string. There is no MPPT in the device and its DC only. Its a lot simpler than a microinverter. Both the optimizer and microinverter are sitting in a very nasty hot environment. Most estimates are that on hot sunny day the back of the panel may reach 180 F. This literally cooks the devices. In both cases long term reliability is lower than a string inverter sitting in a nice cool basement or in the shade. With a string inverter there are MPPT circuits but usually only one or two per array. The MPPT is looking at the average for the string, so in partial shade conditions its going to put out slightly less power than a set of panel level microinverters. String inverters are potentially more reliable. Most new string inverters also can sense the condition of the individual panels and flag panels with problems. Microinverters also talk to a "Gateway" near the tie into the house and can flag panel issues. In most cases the only way you can look at the individual panel data is by having the gateway hooked to the web.

As mentioned communications can be PITA, it seems like the manufacturers are constantly tweaking things and on occasion they screw up the communication. They usually prefer to deal with few dealer than lot of uneducated consumers so the standard answer is call a dealer. Both the micros and the string units can run with out communicating to the world but many want to be communicating so that all the features work. If you plan to sell SRECs or are in state that does grid support (few are doing it currently) or have a battery that ou are getting paid to "lend" to the grid communication is required.

If you add it all up typically a string inverter with optmizers will cost less for equipment but with about the same installation times as a microinverter install. Microinverters, manufacturer specific interconnecting cables and hardware and a gateway will cost more for equipment. For a self install where labor is not an issue then a string with optimizers is the least cost. Installers like to keep it simple and keep it quick. String inverters require a bit more planning at the office and some more inventory as different arrays need different size inverters.Microinverters are more plug and play, less inventory at the shop and in the truck. Less front end work so contractors usually stick with microinverters.

Ideally if the AHJ lets you put them on a non occupied structure like a garage that does not require RSD its the least cost as the mounts are the same as a house but no need for any electronics up on the roof. If you have shade issues from between 8AM to 4 PM at any point during the year lean towards microinverters but if you have full sun year round the string inverter with optimizers may be your optimum installation.



So you
 

Solarguy3500

Member
Dec 3, 2020
194
Western MA
A lot of very good points brought up by @peakbagger

One thing I can say, and this is purely from observation from working in the industry is that although the string inverter with optimizers should be more robust (and was for many years) with Solaredge in particular we have noticed the failure rate increase to a level that is making us uncomfortable with their products. This includes my own inverter that failed at almost exactly the 1 year mark. In fact, they have acknowledged there is an issue to the point that they have shipped us a batch of inverters to have on hand to replace failed units, rather than having to go through the RMA process for each failed inverter.

It is true that the electronics are more involved in microinverters than DC optimizers, but the IQ series micros from Enphase are so far proving to be quite robust from our experience installing them for the last few years. If I had it to do over again, I would use microinverters on my own system.

One other thing I wanted to mention is regarding the statement in the post by @Mr. Kelly about Enphase having a 2 year labor warranty. To my knowledge no inverter manufacturer covers any labor in their warranties, including Enphase and Solaredge. Solaredge gives a standard 12 year parts only warranty with an option to extend the warranty to 25 years for an additional cost of a few hundred dollars, depending on inverter model. Enphase has a standard 25 year warranty but again, it's parts only.

The other advantage to micros, which has been mentioned previously, but bears repeating is that you don't have a single point of failure inherent in a string inverter system.
 
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kborndale

Feeling the Heat
Oct 9, 2008
312
LI
A lot of very good points brought up by @peakbagger

One thing I can say, and this is purely from observation from working in the industry is that although the string inverter with optimizers should be more robust (and was for many years) with Solaredge in particular we have noticed the failure rate increase to a level that is making us uncomfortable with their products. This includes my own inverter that failed at almost exactly the 1 year mark. In fact, they have acknowledged there is an issue to the point that they have shipped us a batch of inverters to have on hand to replace failed units, rather than having to go through the RMA process for each failed inverter.

It is true that the electronics are more involved in microinverters than DC optimizers, but the IQ series micros from Enphase are so far proving to be quite robust from our experience installing them for the last few years. If I had it to do over again, I would use microinverters on my own system.

One other thing I wanted to mention is regarding the statement in the post by @Mr. Kelly about Enphase having a 2 year labor warranty. To my knowledge no inverter manufacturer covers any labor in their warranties, including Enphase and Solaredge. Solaredge gives a standard 12 year parts only warranty with an option to extend the warranty to 25 years for an additional cost of a few hundred dollars, depending on inverter model. Enphase has a standard 25 year warranty but again, it's parts only.

The other advantage to micros, which has been mentioned previously, but bears repeating is that you don't have a single point of failure inherent in a string inverter system.

The only thing I have to add is what you call an advantage of not having a single point of failure, it can be a disadvantage as most people don't pay attention much to their production, so they don't notice a panel or two not producing and it remains out. When the whole string goes out it gets noticed when their electric bill costs money in the summer.
 

ABMax24

Minister of Fire
Sep 18, 2019
1,229
Grande Prairie, Alberta, Canada
The only thing I have to add is what you call an advantage of not having a single point of failure, it can be a disadvantage as most people don't pay attention much to their production, so they don't notice a panel or two not producing and it remains out. When the whole string goes out it gets noticed when their electric bill costs money in the summer.

That's where the monitoring software comes in, I can log in through the APSystems website to see panel level output on my system. My installer can also do the same, his side also shows more details like panel voltage and current, grid voltage frequency etc which can help with diagnostics in the event of an issue without ever setting foot on my property. My installer also monitors all their installs occasionally to check for faults for customers that don't monitor their own equipment.
 

peakbagger

Minister of Fire
Jul 11, 2008
6,635
Northern NH
I have a very sophisticated monitoring system with my three arrays. I walk down in my basement on a sunny day and look at the displays on my two string inverters that are pre RSD and then look at a rack of microinverters for blinking orange LEDs on an ancient system whose string inverter finally failed and was replaced with used microinverters. If the microinverters are blinking they are producing. Once a month I have to make the long walk from my rear door to the opposite corner of my house and read my total production off a production meter and then trudge back sometimes in the snow in winter and fire up the laptop and manually enter my production for the month on a website. I do manual calculation on the months production for my own satisfaction. Every 3 months I get a check for my SRECs and then have to go to the local bank and cash it. Its burden I am willing to live with ;). I do have a spare inverter with dual MPPT with enough capacity to cover both arrays that I bought for cheap and that is my backup as the warranty's are past. If I really want to exercise, I adjust the tilt angle on my pole mount array 4 times a year to optimize production. It take about 10 minutes and a couple of hand tools. I usually adjust my other array that is a wall hung canopy type twice a year to cut down on snow issues. That takes about 15 minutes with a hydraulic jack.

IMHO unless someone has nothing better to do or just plain are into the details, to most people solar systems should be appliances that are rapidly forgotten about.

My next array will be ground mount with manually adjustable angle feeding into a couple of string inverters. No RSD, no failure prone electronics on the back of the panels. I will set them at steep angle in the winter to reduce but not eliminate snow build up issues and then adjust them in the spring to a flatter angle.
 

jebatty

Minister of Fire
Jan 1, 2008
5,793
Northern MN
My system has the 250W Aurora-Power One microinverters installed on a ground mount system located about 250 feet from the main panel. 26 micros installed in 2013 and another 20 micros in 2015. One micro failed about a year after install, replaced under warranty. Two failed about two years ago, also replaced under warranty. Installing the replacements was not under warranty. Replacing a micro is extremely easy (I watched the electrician), takes about 10 minutes. My system has survived and performed well, both from summer heat into the +90F range and to -35F winter range.

When the system was installed I also had an ethernet cable buried to communicate with the micro data collection devices for the micros, although the micros also can communicate by WI-FI, the distance was too far for a reliable WI-FI connection. There are about 15 data points that each the micro has, and checking the micros involves a quick readout on the home computer. The key data is micro voltage, watts and frequency. Most if not all of the data is down-loadable, so it is easy to track performance over time,

FWIW, June 2021 will set a record for total June monthly power output for my system, now 8 years old: 1,890 kWh with one day to go, and I estimate today will produce about another 65 kWh. I have not been able to discern any panel/micro degradation in power output over this period of time.

Our system is grid-tied under MN net meter law, and it produces 100% of the electricity use in our household, including providing most of the power for our two BEV cars.
 

John Galt

Burning Hunk
Oct 22, 2019
119
W Montana
I will set them at steep angle in the winter to reduce but not eliminate snow build up issues and then adjust them in the spring to a flatter angle.
I presume you are talking about weight build up issues. I have mine at a 55 degree angle for maximum winter collection. It still collects roughly the same amount of snow as the flat table next to it, sweeping is easier though which is a daily chore for me. I have seen a foot of snow up there but have never allowed it to build up as it is our only electric supply. The snow won't self slide off until the temps are close to 32 or some part of the black panel shows through.
Thanks for these discussions, I keep learning.
 

peakbagger

Minister of Fire
Jul 11, 2008
6,635
Northern NH
I presume you are talking about weight build up issues. I have mine at a 55 degree angle for maximum winter collection. It still collects roughly the same amount of snow as the flat table next to it, sweeping is easier though which is a daily chore for me. I have seen a foot of snow up there but have never allowed it to build up as it is our only electric supply. The snow won't self slide off until the temps are close to 32 or some part of the black panel shows through.
Thanks for these discussions, I keep learning.
I actually adjust the array angle for snow build up impacting production more than weight concerns. Up in the higher latitudes manual angle adjustment typically gains 10 to 20% over fixed array at the average sun angle which is usually the latitude. I am just south of latitude 45 so a fixed array is around 45 off vertical. I tilt them up to 60 degrees in summer and tilt them down to 30 degrees in winter. I designed the pole mount and its balanced so I can change the tilt myself with just removing two bolts, moving two struts and reinstalling the bolts.

Even at 30 degrees that can build up a lot of snow especially if its east coast snow influenced by the nearby New England coast. Our snow is wetter, Champaign powder is not something the skiers see very often, our snow frequently is closer to spackling compound. It sticks to all surfaces even if vertical. Once it sets up overnight it can require chopping which is not something i like to do with solar panels. There is a fancy auto solar tracking setup made in VT that when it detects snow the panels go vertical and on occasion I see the ones near me vertical covered with snow tracking east to west for a couple of days until the snow falls off. My guess is your snow is lighter and less sticky so its easier to clean. Since ti sounds like you are off grid you have high motivation to clean the panels.

I do sweep my pole mounted panels on occasion as its easy to get to but my roof mounted panels are on the second floor wikth a relatively shallow roof. When they seal up with wet snow it can be weeks before they clear. The only way to get them clean is from an extension ladder and chopping the snow off. I can reach the lower edge with a roof rake and do expose the lower edge, it helps a bit but the array is in two rows one on top of the other, usually the lower row clears but not the top row. Its a small array so I could not split the strings so I need all 8 panels to be uncovered completely. Sure microinverters would help me with production but micros were just coming out when I installed this array and expect the early Enphase's would have needed to be swapped out many years ago.

For remote installations like telecom and seasonal cabins the recommendation is to have a set of vertical panels under an overhang above the highest snow line, the reduced performance from the steep angle usually is offset by cold temps and much higher insolation from sun being reflected off the snow.