madbrain said:
AndyH said:
I didn't say that the company wouldn't consult with engineering. I'm simply trying to separate a couple of areas that many people think are the same.
Nobody implied that they were the same.
I was having a conversation with QueenBee, who suggested that warranty length was directly related to service life, and that we could directly compare warranty lengths for devices in separate categories.
madbrain said:
AndyH said:
Part of the analysis includes the life of the product in the specified application. Part of the analysis includes the terms of the warranty insurance policy (some are supported by insurance, not directly by the company). Part of the analysis includes the likely percentage of those with problems actually filing a claim. More time in service means a smaller return rate for many tech items. A longer stated warranty can often result in more sales. At the end of the number crunching, a company might find that they can risk a warranty longer than their 'average' life.
I'm well aware of that, but if the product really doesn't live beyond the warranty life, the point is that the manufacturer is covering the cost of repair or replacement. Of course I would prefer that neither repair nor replacement be needed, but if they are, I don't care how the cost is being covered, as long as it is actually covered if needed. It is not very important to me if the coverage is provided by the company directly or an insurance company. An insurance company is probably better, if anything, as they may be more likely to be around. But certainly the insurance has a cost, and the insurance company would also evaluate those costs when pricing the insurance policies. The point is that it is taken care of for me.
If I bought a string inverter, the warranty would be much shorter, and nobody currently offers an warranty of 15 to 25 years on them. I haven't seen insurance companies advertising direct-to-consumer string inverter policies either, but if they did, it would probably be overpriced, vs what pricing the manufacturer can get.
Absolutely. I was trying to look at the 'other side' of the warranty. As an end user, we want to know we're covered. Warranty is one way, but so is the company's reputation for taking care of customers.
I know, for example, that Midnite Solar will refurb my charge controller when it reaches the end of warranty. But I also know they'll mail replacement boards or jump through other hoops to make sure their customers are taken care of. It appears that Outback has the same reputation. For both of those companies, I personally don't care how long or short the warranty is because I have a high level of confidence that I won't be left in the dark. If I find in 20 years that I've made a mistake, I still have my soldering iron as a back-up plan.
edit... A bit more searching today provided stories about Xantrex repairing inverters after the 5 year warranty expired (bad capacitors); ExelTech's policy to fix anything that can be fixed, after the warranty expires, for a flat $100; and SMA blind-shipping replacement inverters and paying remove/replace expenses. FWIW.
madbrain said:
For my system, for example, I have some spares for some items that might not be available later in the system's life. If they fail, it may not be worth it to file a warranty claim - I'll simply toss the bad widget and replace it with a spare and go back to gardening.
This seems to me like a good argument for micro-inverters. Even with no warranty whatsover, having a few cheap $125 extra units as spare would be much lighter on the wallet than having buying one extra spare string inverter to avoid downtime.
I agree - and if I used micros I'd keep a couple of spares. There's no way I'll keep a spare VFX3524 in the attic though.
But because I'll have a DC 'critical systems' bus, I'm OK if I have to swap a circuit board at some point down the road. The most likely problem as the inverter ages is the electrolytic capacitors - and I can swap all of them myself for about $200.
madbrain said:
A central inverter is highly repairable - and one is much more likely to want to repair a $2K device rather than a $125 unit.
It might be more repairable indeed, but at what cost ? If you live in a high cost area like California, labor costs are through the roof. The repair might or might not be economical. The string inverters are big and heavy and cost a lot to lug around or ship back. With the string inverter, the entire array will be down too.
Sure, the system would be down for a grid-tied system, but the grid's there for backup. For my off-grid system, the panel-to-battery interface is the separate charge controller. I'll have AC and DC lights, and the water system is DC, so everything critical stays alive if the inverter dies. I can completely rebuild the inverter and the charge controller by swapping a couple of circuit boards, and both Midnight and Outback will overnight boards.
madbrain said:
Whereas with the micro-inverters, only a few panels will likely be down. So the downtime cost will be much less. I would much rather have a quick replacement under warranty and ship one or two micro inverters back in a small package. I do agree that the installation cost will be higher to replace things under the panels, but it still compares favorably with a string inverter repair IMO, and also the manufacturer is covering the cost in the warranty.
madbrain said:
IMO, the fact than Enphase used to offer 15 years standard warranty and now 25 years on their newer micro-inverters speaks to the fact that they expect to be able to honor the warranty somehow. Maybe it's because they really expect their products to last that long. Maybe it's because their products cost more per watt than string inverters in general, so they have more reserves to cover warranty claims. I like to think that it's a little bit of both.
That's fine - but that's your perception. Time will tell if it's correct.
Indeed !
Sorry - bad logic again. Warranty is marketing. Warranty is marketing.
No, once again, warranty is not just marketing, it's also an expense generator for the manufacturer. There are 2 sides to it, not just 1.
Yes, fair enough. Or is it three sides - engineering, sales, and marketing?
edit... Of course you're right that it's an expense generator for the company - and since that cuts into profit, why does a company provide one? So they can sell more widgets and make more profit. While it does require input from engineering, it's a sales/marketing-driven tool. Sorry to beat on this, but that was the whole point of what's become a tangent.
madbrain said:
In the real world of off-grid service, even older tech inverters last beyond 20 years. The newer inverters - with similar designs as the new micros - should last longer. It's commonly expected that if an electronic device survives the first (24 hours, week, month) in service it'll go to end of life unless something like lightning or an installation error kills it. Folks buying central inverters have some history to go on.
I agree string inverters have more history, but where is all the data to backup all your statements about longevity ?
For the thread, I only wanted to show a real-world life beyond the 5-10 year assertion from QueenBee - I wanted to disconnect service life and warranty.
For my own decision, the best I could do was talk with the manufacturers to find out how their earlier equipment is performing in off-grid service, and then adjust for improvements since that equipment was fielded. I started with docs from places like NREL, but most of the 'finished' papers and their service estimates were based on 1980s and 1990s tech, and most was grid-tied, so not very useful.
edit... I still think the paper based on European field studies is 'proof enough' that inverters live beyond their 10 year warranty since it shows inverters doing just that. Since all we really have for the latest batch of microinverters are MTBF and service life projections, why not include info along the same lines from a top-tier grid-tied string inverter company? SMA advertises a 100,000 hour MTBF and greater than 20 year service life - they're projecting a longer actual service life than their warranty. Yes, it's marketing info - but so are the numbers from Enphase.
http://files.sma.de/dl/1371/SB-Info_2001-04_en.pdf
madbrain said:
Why only a 5 or 10 year warranty? Because that's the industry standard for central inverters - that's all they 'need' to provide to entice sales in their niche. They're not competing with microinverters so the warranty rate in that market is irrelevant.
They are most definitely competing with micro-inverters in grid-tie applications. So it's not irrelevant. Most homes are connected to the grid. Do they really want to give up on 99% of their potential customers ?
Yes, they are both options, but from a warranty perspective they are in two different categories. It's similar to the way there are square wave, modified sinewave, and sinewave string inverters - they're in different categories as well.
madbrain said:
I was certainly faced with a choice for my 2 installs between micro and string inverters. Warranty was one reason for my choosing Enphase, but not the only one. Shading is another. It's really interesting when I look at my array how the shade moves around, usually covering one panel almost completely at different times of the day, but never the same panel. I have to wonder how the whole thing would perform with a string inverter. So far it outperformed the original installer predictions by about 20% for the last 2 years. The second array is almost never shaded, though, except by weather.
Absolutely! That's where microinverters or per-panel MPPT units shine - that's the problem they're here to fix.
My application is a passive solar house - shade will be eliminated from the start.
madbrain said:
Microintervers don't have a history. And to add insult to injury, they're going to be mounted under a solar panel - and it's a royal pain to uninstall a row or column of panels to get to the failed inverter in the middle of an array. (Though maybe you have better luck than I and the unit that fails will be on the edge of the array. :lol: ) New products will generally NEED a longer warranty - and devices intended to be buried under solar panels with a 25 year life should have a similar warranty. Otherwise, Outback, SMA, and other companies will keep selling central inverters to these customers.
I don't dispute that the replacement might be a pain. But again this is something covered by the manufacturer warranty. What matters to me as a PV user is the total cost of ownership over the long term, and getting the most electricity production for the lowest possible cost. The micro inverters are among the most expensive per watt, and time will tell if the extra production and promised reliability are worth the cost. I am very happy so far over the last 27 months, having saved over $8000 in PG&E bills. The payback for my first 28 panel system will be a total of 7 years, for the second one with the 12 panels I just added only 4 years.
I will read the article you posted.
No worries about the article, it was warranty related. The piece from Yale is probably more relevant but it has nothing to do with PV either.
http://www.econ.yale.edu/seminars/apmicro/am09/ishii-091001.pdf
edit... You might enjoy this thesis from 2011 - it's a small SMA string/Enphase side-by-side:
http://libres.uncg.edu/ir/asu/f/Lee, David_2011_Thesis.pdf
I'm not against micros in any way and hope that I didn't come across that way. I just bristle a bit when one of our resident salesfolk starts throwing mud at the old-skool equipment. :lol:
I hope your system serves you well for a very long time!
Yet...another...edit...
Beware - inverter guts!
Swapping circuit boards in an Outback FX inverter - two parts:
http://www.youtube.com/watch?v=cb2PpRs9Bss
http://www.youtube.com/watch?v=fVwpHCsoKJA
Ditto for a Midnite Classic 150 charge controler:
http://www.youtube.com/watch?v=mkzYfSy75No