For those of you that want an easier way to understand the differences between microinverters (such as those manufactured by Enphase or APS) and DC optimisers (such as Solar Edge or Tigo), and don’t want to read this long post I published a couple of weeks ago then this 2 part infographic is for you!
The first part explains the difference between conventional, string inverter systems, DC optimised systems and microinverter systems (seasoned solar nerds may want to skip this and scroll straight down to part 2)
Microinverters vs DC Optimisers. Part 1
Part 2 goes into the pros and cons (and even picks a winner based on my humble opinion).
MIcroinverters vs DC Optimisers. Part 2
If you want to republish any of these infographics, no worries. All I ask is that you link back to this original post. I also have higher res versions which I can provide. Just ask!
* Note: the 2nd graphic has been updated to include 2 features of full Solar Edge systems (i.e. systems with Solar Edge optimisers coupled to Solar Edge Inverters) . Specifically Arc protection and individual fault bypass circuitry.
** This is only an opinion! If you vehemently disagree with my analysis, please leave a comment, or even write a well articulated blog post with your differing opinion, and I will happily publish it.
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Thanks for the insightful articles. We have installed a lot of microinverters then switched to SolarEdge about 2 years ago. While in theory microinverters may win the robustness battle, in actuality we have not found that to be the case. We regularly have microinverters go bad and need to replace them (note: Enphase has been very good about honoring their warranty). We have even had to replace microinverters we’d already replaced. In the 2 years of SolarEdge, we have not had a failure.
Mark
I still disagree with your assessments on a practical (I’m no engineer) level.
1….Lifetime cost. Since there’s no indication that the micro units are any more durable than the string inverters (and less so on the evidence of Mark Bortman) the projected ‘lifetime cost’
MUST be related to initial cost…and applicable warranty.
Moreover, given the far more exposed installation of the rooftop units it’d be fair to assume they’d be far less durable. And finally, the rooftop positioning would make monitoring and replacement, etc. more complicated —> expensive.
2…….Flexibility. How’s that an issue? It takes all of 2 minutes to match the number of panels to the size of string inverter you require. Connecting x number of panels required in either case is more complicated, expensive and risk-prone when you have to connect a dozen or two separate panels (each with + & – cables) the entire distance to the meter-box. ditto ‘system expansion’.
3…..The same applies to “ease of installation”. Assuming 20 panels, you need but TWO (or four if you choose 2 strings) cables/protective conduits/whatever to run from roof to ground. With each panel separately connected you need FORTY cables.
4….Scalability. Proper initial assessment should preclude the need to upsize a system. In any case,
if you MUST upsize string inverters are not only much cheaper right now, but are still getting cheaper. (down to a few hundred dollars if you bide your time/check ‘sales’, etc.)
5…..Battery storage. Micros are not only more expensive to buy and install, but involve the added cost of power-loss on at least two levels. (a) converting AC to DC creates (what?) 10%-15% loss of energy depending on unit efficiency and (b) each extra connection also creates losses.
6….Robustness. “Fault-detection” is most simply and effectively achieved by a person monitoring their system. (I do so daily at least: a glance at the inverter is all it takes to notice if something isn’t working properly.) If the whole system goes down due to one panel-failure you’re aware of it almost immediately and can fix it.
Not so if one or two or even three panel(s) out of 10 or 20 goes down. Anybody stupid enough to install panels where they can be shaded by trees/etc. shouldn’t be allowed within rifle-shot of ANY kind of electricity.
7~ finally!…SAFETY!. In general, given proper components/installation (and MORE than ‘adequate’ cables, switches,fuses, earth-connections, etc.) there’s absolutely no reason to suppose ANY DC voltage is more dangerous that AC voltage. Quite the reverse!
……Specifically:- When was the last time anyone saw a suburban train (or Melbourne tram!) which run at voltages of 1500 VDC catch fire or go into melt-down in well over 100 years of use?
Google doesn’t list a single case.
On the other hand, there are about 4000 house-fires in Melb. each year, over 80% of which start from ‘electrical fault’ ~ @ 240VAC ~ and installed by qualified experts!
Incidentally, has anyone here heard of any house that’s ever burned down due to a solar-system?
….particularly a stand-alone system installed by an unqualified owner-builder. No? Me either.
….Back to the drawing board, Finn?
ps…and let’s not forget the massive, lethal bushfires which are often caused by ACVoltages.
Just an afterthought:- How do ‘optimisers’ vary in function from a simple inline diode on each panel ~ which can be installed in three minutes and cost about as much as a fancy cup of coffee?
I have 2 phase connected to my house, I don’t have any 2 phase appliances, so with Micro Inverters, could I run some on one phase, and some on another? is this possible with a string inverter ?
You can either put half the micro inverters on each phase or simply put them all on one phase. It won’t make any difference to your export calculations as they are all netted in the new meter. You can use a 1-phase string inverter on one of the phases for the same reason/
This is an old article, are the conclusions still valid?
One thing left out due to the article’s age is, after a few years of delay, Maxim optimised panels are now available and do a similar job:
https://www.solarquotes.com.au/blog/maxim-just-killed-microinverter-dc-optimiser/
Because of their relatively low cost it will be interesting to see what effect they have on both microinverter and optimiser sales.
But are they in the Australian market? I heard they pulled out.
They were, then they weren’t, but now they’re back again. Generation 1 failed because of interference with TV reception. Generation 2 apparently failed for the same reason. I haven’t heard of any problems with Generation 3, so I assume they’re okay, but they seem to be taking a low key approach and you may have to look around for someone who installs them.
I commented on this back in October of 2015. Recently (over the past year to year and half), we have been encountering a lot of reliability problems with SolarEdge (both inverters and optimizers) and their customer support has been atrocious. We have been transitioning back to Enphase. Their latest generation microinverters, the IQ7 series, has proved to be relatively reliable. I’m looking forward to their IQ8 series, if it ever actually comes to market.
Thanks heaps for the update Mark. You’d won me over with your first comment, and then won be back around in the other direction with this second comment.
…lol here’s hoping I don’t check back and see a third comment after I get my Enphase system installed!
If you have microinverters and want to install battery storage in the future how is this addressed and what is the current approximate cost.