Need to decide on a system design 6.3 kW - San Marcos

[gvl]

Yes, to me that is actually the biggest advantage of micro inverters.

On the other hand they require up front premium over string inverters or even Solar Edge, which can be as high as 50% of new central inverter cost.

[thejq]

Heard back from vendor 1. Conduit will run through the attic. In a discussion with him about micro inverters vs string with power optimizes, he indicated that both are newer technology and he actually prefers the simplest approach with just a string inverter. He said SMA is a proven inverter that has been in business for 30 years and that Enphase and Solar Edge are not profitable companies at this time.

So now he has confused me even more on what would be best for my situation. Regardless of 1% or 2% efficiency differences, I want reliability the most since I will own it and have to deal with a problem should one arise and the companies don't exist anymore years from now.

If you have 3 or 4 roofs to deal with like you said, SMA will not work. If however you can limit that to two relatively balanced roofs and have no shading, then SMA with dual MPPT should work for you. SMA is a very reputable company, you can't go wrong with them in terms of reliability, but you do loose the per-panel monitoring capability.

[sensij]

theTE=thejq;150712]So you agree with me that the reason for clipping is because the system is approaching the limit. Raising the voltage is a way to maintain the equilibrium so the system doesn't go over the edge (too much current). The clipping examples were analogies to illustrate clipping is almost always bad no matter what modes you're talking. It don't think it takes a genius to figure out which is a better system -- one that produces less and constantly at the hairy edge of its limit, and one that produces more and always have margin to spare. So remind me what part of my reasoning is"wild speculation"?[/QUOTE]

you are speculating that there is a cliff in inverter life... that somehow, if.that M250 inverter were to accidentally produce 251 W, it would disappear in a puff of smoke. that is very unlikely to be the case. the enphase inverters are warrantied for 25 years. whether or not they will really last that long is unknown, but you have provided no evidence against it, or that the chances of reaching that life are improved by pairing with a 250 a panel instead of a 305 w. the proposed design is within normal design parameters, and the warranty applied. unles you happen to work for emphases and know how much margin is in the design, your comments about when they will fail ars pointless.

[thejq]

you are speculating that there is a cliff in inverter life... that somehow, if.that M250 inverter were to accidentally produce 251 W, it would disappear in a puff of smoke. that is very unlikely to be the case. the enphase inverters are warrantied for 25 years. whether or not they will really last that long is unknown, but you have provided no evidence against it, or that the chances of reaching that life are improved by pairing with a 250 a panel instead of a 305 w. the proposed design is within normal design parameters, and the warranty applied. unles you happen to work for emphases and know how much margin is in the design, your comments about when they will fail ars pointless.

Oh boy, now you're just putting words in my mouth. When did I say it would disappear in a puff of smoke? The exact word was "longevity". Failure rate is a probability with sufficient statistics. Enphase is the only one with that "evidence". All I'm saying is that micro-inverters are no different from other electronic or engineering products. If you run it at max limit for extended period of time, it's longevity will suffer. It's based on common engineering sense and intuition. If you want more "evidence", how about the ever changing warranty terms (10-yr to 25-yr to removal of labor cost after warranty obligation ballooned). BTW, what's your evidence that says consistently running at limit is perfectly fine beside what Enphase tells you. I don't think Enphase is a bad product, just don't run it at clipping for a long time, that's all. I feel that the thread is getting digressed, so I'm resting my case now regarding clipping and longevity.

[hockeydude]

On the other hand they require up front premium over string inverters or even Solar Edge, which can be as high as 50% of new central inverter cost.

gvl - So if I have a quote for the Enphase at $3.55 / watt with installation on 3 or 4 roof surfaces it seem like a decent price. I see from all the posts that there is some risk in going with the micro inverters since there is not enough history on the M250 to really know their reliability or even the long term viability of the company. Same seems to hold true for the power optimizers since they don't have a long history.

Bottom line no one wants to have to deal with a warranty as they don't seem to have much value especially after 10 years. You will end up paying for something if it all goes bad. I just want the things to work for a long time and it appears that at this point there is no real good way to know what will happen. All of this technology should be better (and hopefully cheaper) 10 plus years from now so repairs should probably be expected at some point. Even with this unknown, purchasing still seems like the best option compared to a lease.

[J.P.M.]

gvl - So if I have a quote for the Enphase at $3.55 / watt with installation on 3 or 4 roof surfaces it seem like a decent price. I see from all the posts that there is some risk in going with the micro inverters since there is not enough history on the M250 to really know their reliability or even the long term viability of the company. Same seems to hold true for the power optimizers since they don't have a long history.

Bottom line no one wants to have to deal with a warranty as they don't seem to have much value especially after 10 years. You will end up paying for something if it all goes bad. I just want the things to work for a long time and it appears that at this point there is no real good way to know what will happen. All of this technology should be better (and hopefully cheaper) 10 plus years from now so repairs should probably be expected at some point. Even with this unknown, purchasing still seems like the best option compared to a lease.

On the lease vs. buy thing: At $3.55/Watt, any upfront $$ benefit a lease may have gets pretty small.