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Comparing solar quotes and wondering about installation experience
- Thread starter sleepy
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nwdiver
Well-Known Member
It's going to almost if not entirely impossible for installers to compete with Tesla on cost. Tesla has cut everything to the bone. Most Solar companies spend almost ~$1/w just on getting customers, Tesla spends $0. It's going to be interesting to see how this plays out. Tesla has pretty much 'broken' the industry.
Yet, even Tesla prices are double of what people in places like Australia pay. Are US labor rates that much higher?
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nwdiver
Well-Known Member
I'm sure that's part of it. I still occasionally hear of installers charging >$4/w. It's insane.
My system has been online for 18 months, it's amazing how much the solar install environment has changed in that time. Tesla was unable to get started on my system in a timely manner and didn't have a price advantage at that time like it does now. They did have the cheapest Powerwall quote so I went with a local company for the solar system and and Tesla for the Powerwall, so that may be an option for you as well. There were some minor problems getting the Gateway to work properly with the solar system that may have been avoided by doing it all with one company. At the time Tesla was using the same panels as my installer (Panasonic) but now with the rock bottom prices the panel quality and system design may have some compromises? Most people overlook the inverter sizing and optimizers on their quote. I think nowadays it's very hard to not go with Tesla because of the system cost savings.
nwdiver
Well-Known Member
There's really no significant difference panel to panel. A solar panel is really just a piece of laminated glass. I don't think people really appreciate just how simple solar panels are. Technology improvements filter across the industry into all manufacturers and you get what you pay for in terms of efficiency.
It's also rare for optimizers to provide any real benefit. I suspect that Tesla has started using them as a default for the same reason micro-inverters are popular... math is hard and it's easier to just throw panels on a roof without worrying about string length.
I don't know if you're right or wrong on either one of these, but I'd bet against you based on my experience with Chinese manufacturing and articles like this:
Backsheets are shortening some solar project lifespans
Optimizers aren't just about production, they offer a safety shutdown feature that might prevent your house from burning down. In terms of efficiency you're basically arguing that MPPT converters aren't worth it, which is a hard argument to win in my opinion.
nwdiver
Well-Known Member
Almost all panels come from China now. Some percentage are going to have problems no matter where they're manufactured. Here some made in WA State that were becoming delaminated and catching fire.
You don't need an optimizer to protect your home from burning down. AFCI protection is now required in all grid-tied inverters... that serves the same function. I'm not arguing that MPPT converters aren't worth it... they certainly are... on the STRING level not module level. And more of an explanation than an argument. I've installed Solar Edge systems with optimizers and string systems. There's no noticeable performance difference and certainly not one worth the increased cost of optimizers.
Even for rapid shutdown there are options 70% cheaper than optimizers.
I'm not sure whether string fault protection is as good as panel protection. I do remember you posted about this optimizer topic previously:
Optimizers... what are they good for?
so I'll just leave it at that.
nwdiver
Well-Known Member
In the VERY, VERY rare case a fire starts in a PV system it's usually one of two things. Either a high resistance connection which eventually melts, separates and arcs; which AFCI is just as good as quenching as rapid shutdown or an internal short in the panel itself which neither can do anything about.
The purpose of rapid shutdown is to protect fire fighters from high voltage when they cut through solar panels on a roof. Which I've always thought was idiotic because there's no good path to ground. I've never heard of a fire fighter being shocked by a solar array.
And they didn't charge me for less conduit. They ended up cutting the total conduit runs down by 60% or so just by going through the attic. The stall foreman said they normally charge for attic runs but were waving it because of ease of attic access and reduced materials. It took them about 10 minutes to run all the conduit through the attic.
How will I know what my panel level production is without optimizers or micro inverters??? And if there's ANY panel partially shaded in that string MIs or PVOs will absolutely matter.
nwdiver
Well-Known Member
It's incredibly rare for a panel to fail after installation. I've never seen it. You can verify panel production by comparing strings. While I'm not a fan of module level optimization string level does have benefits. You can see the current and voltage of each string.
As was linked to earlier. Bypass diodes solve the shading issue.
This system doesn't have any optimizers... but I can compare the strings to ensure all panels are working. If 1 panel failed there would be a noticeable deviation in voltage or current. There's a difference here because one string has 5 panels and the other has 6. So the voltage in the blue string is expected to be 5/6th of the green string.
That's cool, but when that corner panel gets reduced from 340 to 300 because the tip of one of my redwoods is shadowing it, I don't want the entire string to suffer.
I also want to be able to clean the lowest easily accessible panel from time to time just to see how difference it makes earliest in the morning when oblique sun has a harder time getting through the dust and how that panel compare to other panels. The condensation is very uneven so I need to compare that cleaned panel in the early morning to a higher up panel that no longer has the condensation but is still dirty.
And mostly because I'm a geek and I just want the data. I'm hoping I can import into my Splunk server because I plan to write my own dashboards.
I also want to be able to clean the lowest easily accessible panel from time to time just to see how difference it makes earliest in the morning when oblique sun has a harder time getting through the dust and how that panel compare to other panels. The condensation is very uneven so I need to compare that cleaned panel in the early morning to a higher up panel that no longer has the condensation but is still dirty.
And mostly because I'm a geek and I just want the data. I'm hoping I can import into my Splunk server because I plan to write my own dashboards.
In the same situation as OP - trying to see if Tesla solar panel installation might be the right option. I am strongly considering a local vendor who installs LG panels and Enphase microinverters for $2.29 (before federal & state rebates), where as Tesla at $2.01. I am more comfortable supporting local business, plus the ease of picking up the phone and directly taking to my installer, as opposed to calling a call center and having them route my issue to the right team.
I am surprised though that even after the price difference between the local installer and Tesla, I do not see any price difference for the overall PV install. With 20 LG 360 panels, a 7.2kw system is expected to generate 7413 kwh because the panels are being placed where we get the most sun. It seems Tesla installs panels in rectangular blocks, and this would require them to place 9 out of 24 panels on the rear roof where we do not get less sun. So, a 8.16kw Tesla system would generate 7,549 kwh. Even with 4 extra panels, Tesla would generate only ~150 kwh more than LG system and erase the price benefits. The difference between both quotes is under $100.
Wondering if Tesla is being conservative with their production numbers so the utility approves it, or the production would indeed be as low as they quote.
I am surprised though that even after the price difference between the local installer and Tesla, I do not see any price difference for the overall PV install. With 20 LG 360 panels, a 7.2kw system is expected to generate 7413 kwh because the panels are being placed where we get the most sun. It seems Tesla installs panels in rectangular blocks, and this would require them to place 9 out of 24 panels on the rear roof where we do not get less sun. So, a 8.16kw Tesla system would generate 7,549 kwh. Even with 4 extra panels, Tesla would generate only ~150 kwh more than LG system and erase the price benefits. The difference between both quotes is under $100.
Wondering if Tesla is being conservative with their production numbers so the utility approves it, or the production would indeed be as low as they quote.
nwdiver
Well-Known Member
It won't; That's the misinformation that's been spread about string inverters. The shaded portion of the panel is 'deleted' by the bypass diodes. All panels are divided into 3 cells groups with 3 bypass diodes. Some newer panels have 6 groups. If any group experiences enough shade the diode opens and current is directed around the shaded section. The same effect occurs with an optimizer so if 1/3rd of a pael is shaded an optimizer would make no difference.
I agree the data is cool. I just don't think it's $40/panel cool. We're installing a 8.3kW system this weekend. Using optimizers would have added >$1k to the cost.
Both numbers seem low to me, do you have a lot of shade on the roof? Your profile says that you are in New Jersey, so a quick PVwatts calculation for Sussex, NJ with 7.2kw of panels all facing south says 9459kWh annually.
There have been users here that said that Tesla is being conservative in their numbers relative to PVwatts, but my personal situation was the opposite with the Tesla estimate being higher than PVwatts. Having a lower number raises less red flags with utility PTO applications in cases where the system is oversized relative to your last year(s) of annual usage.
Mentioned some of this on another thread, but a couple notes here. First, Tesla's first layout effort seems to often be sub-optimal, and you can request a re-design with specific suggestions. They do sometimes seem to prioritize aesthetics (having nice rectangles) over production. It is, of course, also possible that the size of the Tesla panels is just enough larger that for your roof they have to move more to the rear roof. It is also possible that Tesla and/or the other installer has incorrect data about local setback rules.
To double-check the numbers from each installer, use PVWatts Calculator to see what it reports. I would not be shocked if the Tesla numbers go up over 8k kWh. I do not know about your local installer.
All that said, I certainly could see the potential advantages to paying more for a local company who will be responsive during the install. The only thing to check with that is what their warranty is and who will be around in 5 or 10 years to address issues.
My first layout had half the panels facing east even though I had plenty of room on another south facing section of roof. I asked them to move it and they did no problem which is where the did the actual install. I can only think the reason is that would have save about 130 feet of conduit because not only is that section on the opposite side of the house from where the inverter is, it would have been a lot of work to route that conduit through 25 plus bends (because of the many elevation changes of my rear porch to get all the way around.
As it turns out, they went through the attic which was only 40 feet but even that was still and additional 40 of conduit they wouldn't have had to use had they kept that east facing position.
They're own yearly kwh estimate AFTER the revision went up by 1300, it pretty large jump. Not only that, but the new position gets me many more kwh of peak production that I would have missed out on facing east.
I'm glad to hear you had no issues with your Tesla solar install. Same reports from 4 neighbors, including one who recently got a new inverter under warranty. If we can save $10k-$15k, I don't mind being the project manager.
