How did you decide? Microinverter vs Optimizer & PV Inverter

[ButchDeal]

many would disagree with you there. Most people looking for backup with battery particularly in coastal are ok with limited power (no AC or other big loads). so a 400-600ah 48V system works well. They generally have sun after the storm in some form so 2-3 days of no sun run time generally equates to pretty much indefinite.
All common backup solutions have critical load panel.

I never stated that this was enough to swing the market. Others stated that battery would save enphase, and I pointed out that currently the largest residential battery market in the US is for backup, which enphase is not hitting.
Enphase system could be adapted to be a backup solution but it would be much more complicated in that role.

[J.P.M.]

I'll bet there're guys here who live in the hot southwest who can tell us based on panel voltage pretty accurately what temps panel silicon can reach. I'd like to get an inkling of that. Silicon diode voltage decreases by about -2.5mV/C. The actual frame of the panel will be somewhat cooler.

I can, but it'll take more space than available here. Been at it for ~ 2 1/2 years now.

Very short guess on array temps.: In winter, under something like 800-850 W/m^2 POA (Plane Of Array) irradiance, my roof array runs 23 - 23 deg. C. above roof ambient air temp. which runs about 3-5 C. above ground level ambient air temp. at midday under clear skies. In summer, Approx. same conditions, w/POA ~ 950-975 w/m^2 POA irradiance, the array runs about 24-26 C. above roof ambient air temp. which runs ~~ 4-7 C. above ground amb. air temp. One correlation I've found that gets pretty close to what I've measured:

T, array ~~ = 0.943*(Tamb. ) + (0.28 * (I) -1.528 *(wind) +4.3 (from NREL/ CD - 520-33586, yr. 2003.)

Where: Tamb, = amb. air temp., deg. C.
I = P.O.A. ( plane of array) irradiance - not GHI ( Global Horizontal Irradiance)g, in W/m^2
wind = wind velocity in m/sec.

I needed to change the last term to 3.82 to better fit my observations.

There are lots of other methods and correlations. One way to use Voltages: Observe/record array voltage at the inverter. calculate/estimate the array temp. using the above empirical correlation. Do this several times and see if a pattern/trend line emerges, or get the Voltages from your monitor. Either or any way, compare the slope of the voltage drop/deg. with published data for the temp. coeff. of Voltage for the panels in question.

That's the Reader's digest version. Some assembly is required. Your mileage will vary.

[ltbighorn]

Fair point. It seems seems like it'll be a very long time before batteries present any real competition to backup generators for people suffering from coastal storms or other extended duration outages, due to the cost of suitable sized batteries (even with major reductions in cost - the capacities needed for extended backup power are often an order of magnitude larger than load shifting batteries, unless homes rewire for a critical loads subpanel). I'm not convinced that the subset of people with unreliable grids (frequent, short outages) is substantial enough to swing the market. If there does turn on to be surprising demand, to the point where it's inhibiting adoption of systems, is there anything stopping from Enphase from creating an automatic switch+transformer just like SolarEdge? Both are very simple devices.

[jflorey2]

But saying I am throwing out things like being 10-15 degrees cooler in the shade of the panel/module? Ever stand in the sun and felt the heat? Ever stepped out of the sun and into the shade? Yes, it was a little bit cooler! I don't need to have a degree in physics or thermal dynamics to offer this observation.

Case in point -

We were in Thailand and the Thais had thoughtfully provided some packing tents. It was 90 degrees and 80% humidity. You would step out of the sun into the black tent and . . . immediately be hotter. The black tent absorbed all that sunlight and re-radiated it as infrared, and the slight reduction in wind (even though three sides were open) was enough to make it much worse.

So yes, in some cases, being in the shade is going to make you hotter. It all depends on mounting, amount of shade, amount of air circulation, and both the radiative and conductive thermal environment.

[ButchDeal]

Sure eventually tou will but other battery solutions do both load shifting and backup. People that have gone through major costal storms and/or regional rural outages are a bit more intently interested in the backup capabilities.

[ltbighorn]

People asking about batteries today are interested in them in the same way people asking my about electric bikes ask if I pedal it to recharge the battery. They don't know what matters or makes sense and so they think the most relatable aspect. Oh, batteries, that means I can run it without the grid, right?

People who need off-grid capabilities today will certainly look to those systems, but the desire to cover for infrequent and brief grid outages seems unlikely to be a major driver of expensive batteries, something that may not ever be cost effective. At best it's a high cost for a perceived utilitarian benefit for some. On the other hand, increasing rates and steep TOU ratios are likely to eventually make load-shifting with batteries a gainful financial calculation for large swaths of people (region dependent, certainly), and that seems much more likely to drive sales than backup power.

Backup power is probably #25 on my list of nice-to-haves, but being able to load-shift over TOU periods? That's something I'll do the moment battery prices fall enough for it to pencil out. Backup power has no such point.

[ltbighorn]

PLEASE NOTE: Im not trying to convince anyone that Enphase is a good investment, or tell anyone how they should weight this information in their decision process. I just spent some time as a casual observer and potential product purchaser, looking into Enphase's situation, and am sharing some info/thoughts that are not necessarily apparent just by looking at their stock price or their last couple quarter financial reports. I am by no means a financial advisor/expert.

Enphase certainly looks to be in a difficult position financially. SolarEdge looks like the hotness right now, and that's certainly a more comfortable and higher odds position, but if there's anything I've seen in technology it's that that's no guarantee either. I've seen the tides turn rapidly so many times. Going into my selection I figured good chance that neither SolarEdge, Enphase or my installer are around in 10 years to service warranty claims, and so I'd rather not pin my satisfaction on someone honoring a warranty 15 years from now. While it'd certainly be disappointing if Enphase got into a situation where it couldn't honor warranties in the next couple years, that particular situation feels less likely to me due to the number of alternative outcomes to straight-out chapter 7 and shutdown (acquisition, restructuring, etc.), even if their financials never improved.

That said, listening to their investor calls gives some more perspective on their position. To summarize for people who don't have the interest/time, here are some highlights:

- they've explicitly chosen the strategy of thinning gross margins and suffering some losses now in order to regain/grow top line revenue and marketshare as they work on executing their cost reduction plans, which should help improve margins again
- they have working capital arrangements on the order of $75M+ w/no significant covenants/stipulations that would prevent its use -- they feel these are sufficient to cover their anticipated cash needs without selling more equity etc.
- a big part of their low cash situation is from an excess inventory (they have $45M of inventory on hand). They've kept production up in anticipation of improving sales, but still intend to draw down the inventory level as they consider it to be too high
- their 6th gen product isn't released yet, but isn't quite what I'd call vaporware. It exists now and is undergoing QA/accelerated lifetime testing, etc for release later this year.
- they're currently on target to meet their cost reduction goals (cost of producing inverters) set for both 2016 and 2017. If they continue to hit those then that should help their margins, even in the face of further price reductions. it's in their targets to become cost competitive with low-cost central inverters.
- they saw good effect from their price reductions and found that people were still willing to pay a premium for the enphase product over competitors (obviously as long as the premium isn't too steep). competitors made moves to counter enphase's price reductions but it didn't mitigate the gains to enphase.
- they haven't had any issues with accounts receivable or credit with suppliers etc.

What do I think you can take from that? They're still in a tough situation, but they're not in a panic mode -- they could do several things to decrease losses in the short term, but they believe they have the reserves to execute on a better long-term strategy for growth/profits/competitiveness. How successful they'll be certainly remains to be seen.

Based on the field MTBFs I've seen from the M215 and M250s, I personally don't think 100% of them are going to suddenly keel over. Of course, no one knows for sure. Should Enphase's outlook continue to worsen, I can get some spares at a very low incremental cost ($100-$150 per), and I can easily switch to an alternative vendor for future expansion without significant sunk costs. If roof access wasn't easy for me, I'd likely be going with a SunnyBoy Fronius rather than SolarEdge to much more substantially mitigate the risk of roof visits. Electrolytic capacitors are by no means the only reason (or necessarily even primary reason) that electronics fail.

[DaveDE2]

I'll bet there're guys here who live in the hot southwest who can tell us based on panel voltage pretty accurately what temps panel silicon can reach. I'd like to get an inkling of that. Silicon diode voltage decreases by about -2.5mV/C. The actual frame of the panel will be somewhat cooler.

[entgegnen]

Hi sensij,

The discussion that went over my head was this:

"To a first approximation, when A is close to B, A⁴ - B⁴ is proportional to 4(A-B) (Average)³ As the temp difference gets very large the heat transfer becomes proportional to the fourth power of the higher temperature. In between, it is messier."

Thanks.

[sensij]

The discussion of heat transference has quickly gone over my head. But I did notice a comment on a panel/module reaching 60 centigrade (140 fahrenheit for us non-science types) Based upon the relative positioning of the physically integrated micro inverter I have no reason to believe it would be a temperature of anything much less than 140 farenheit. By contrast, a rail attached module like Enphase would seem to be 10-15 degrees fahrenheit cooler. (do to air, being in the shade of the module/panel etc. Maybe 10-15 degrees doesn't matter. I just suspected it would over time. I've seen anecdotal posts of panels/modules getting as hot as 170 degrees in southwest summers. FWIW, Enphase literature does mention conducting testing that included 50 days at a constant 185 degrees fahrenheit (for something called an IEC 61215 test). So maybe they are built to hold up.

The discussion went over your head, but you are still offering estimates on how much cooler one microinverter would run than another? Nice. In your engineering assessment of the installation, are you making an adjustment for a difference in conductive heat sinking based on the contact area on the frame relative to the contact area on the rail? That 10-15 deg number is completely made-up... it is fine for you to use it in your own decision making, but I want to make sure that others reading this realize there is no substance to it.

[entgegnen]

I for one an "cheering" for both companies and both technologies. I'd rather folks have good jobs than not. But obviously, company strength does come into play when considering a system that has a 25-year shelf life. It does seem that Solar Edge has more proprietary stuff, and that the apparent diversity of micro converter companies is a strength (if not for Enphase, for the technology). That being said, the strategic partnership between Solaredge and Tesla could also be a great longevity factor for product diversity (bolstering Solar Edge).

One comment above noted the financials. I too noticed the quarterly direction. (Although I had not fully researched any markdowns, potential litigation, or other reasons for it. There could be reasonable reasons for the direction. But this late into company existence is usually not the best sign. I am not a financial advisor.)

The discussion of heat transference has quickly gone over my head. But I did notice a comment on a panel/module reaching 60 centigrade (140 fahrenheit for us non-science types) Based upon the relative positioning of the physically integrated micro inverter I have no reason to believe it would be a temperature of anything much less than 140 farenheit. By contrast, a rail attached module like Enphase would seem to be 10-15 degrees fahrenheit cooler. (do to air, being in the shade of the module/panel etc. Maybe 10-15 degrees doesn't matter. I just suspected it would over time. I've seen anecdotal posts of panels/modules getting as hot as 170 degrees in southwest summers. FWIW, Enphase literature does mention conducting testing that included 50 days at a constant 185 degrees fahrenheit (for something called an IEC 61215 test). So maybe they are built to hold up.

[ButchDeal]

You tried to claim that their financials would be improving based on a road map (every tech company has one), vapor ware (S300), and the very limited release of an AC battery.
The actual financials for enphase are pretty clear if you look at them quarterly over time. They had some market share but couldn't maintain it, and couldn't keep up with advances in technology as fast as the rest of the market. Is it recoverable? yes. But based on the battery? No. The battery is likely a loss leader anyway. Based on the S300? possibly if they can get it out quickly. The real point will come if they can get their bos costs down. (not the same as reducing price AND profits). So far their roadmap doesn't seem to show this happening. Well it does but it assumes that all their competition is standing still, which they are not.

[Engineer]

OH give it a rest.

[ButchDeal]

Many links in a thread on this board, both from the company and from distributors, a search will find it. Response was, I forget the number but twice what they expected or thereabouts.

It's not a BACKUP system and is not designed or advertised as such, do some research and you'll understand it better. It is opening in Australia only at first for good reasons, the same ones every other manufacture is doing the same thing. US release is later this year.

twice a small number is still a small number They are late brining the product to market, day late, few dollars short so to speak.

I understand it very well. Yes they specificially do not mention that it backs up BUT they attempt very well to hid that it does NOT.
Almost every customer asking about batteries is interested in backup.


Expecting a limited capability battery system to save the company from poor financials is pretty far fetched.
Do some research and you will understand the product, market, industry better.

[Engineer]

where do you get the AC battery has a huge response? They have barely opened any markets with it, and it is lacking in the primary feature that people want with a backup system, BACKUP.

Many links in a thread on this board, both from the company and from distributors, a search will find it. Response was, I forget the number but twice what they expected or thereabouts.

It's not a BACKUP system and is not designed or advertised as such, do some research and you'll understand it better. It is opening in Australia only at first for good reasons, the same ones every other manufacture is doing the same thing. US release is later this year.