Optimisers or micro inverter?

I

izzypops

Hi. I'm looking to get a full 4kw system installed and have had 3 quotes. 1 I dismissed as the company didn't check out too well. The other two quotes appear to both be reputable companies with all similar credentials and warranties. The main difference is one is favouring solaredge and the other enphase. I have had long discussions with both but appear to be no further forward. Again I've tried to research the two options online but again to no real benefit. It seems both systems are pushing the same benefits in their own way. The enphase is very slightly more expensive, but has longer warrantee. Is this worth it?
 
What are the shading issues - a well designed string system using Power-one or SMA inverveters can both outperform enphase or solarredge.

We have installed all three technologies, and it is very dependant upon the configuration - how many roofs, how amny panels per roof, what orientation and elevations and what shading affects the roofs.
 
Have east pitch for 11 panels and south 5. The main issue is one pitch shading another. All 3 companies quoting suggested one or another.
 
Enphase has no single point of failure whereas the Solaredge system will completely stop if the inverter fails. So with Enphase you lose 1/16th of your 4kW system compared to all of it with Solaredge inverter failure.

Enphase outperforms Solareddge according to the ONLY independent test results available from PV evolution labs at :- dated Sept 2013 so very current.
http://www.metgen.co.uk/assets/download/index/assets/122/

There are three U tube videos available here about why Enphase is better
Enphase Inverters | Solar PV & Renewable Energy Trade Supplier | Metgen, UK

There is side by side testing regarding Enphase v SMA but it is a little dated and I need to find the link for it.

Solaredge seem to shout the loudest about being the best and keep on about Enphase capacitors failing despite the fact they and SMA use the exactly the same capacitors. We have over 100 Enphase systems and have had one unit fail as a squirrel decided to eat the cable which is hardly the manufacturers fault.

There is some evidence that systems over 14 modules are less efficient with Solaredge.

We have used all three systems but now only fit Enphase and SMA as both of these have superb customer support whereas Solaredge back up is patchy at best.

The Solaredge optimiser unit is about £30 on eBay and the Enphase micro over £90
which is also a guide. The Solaredge optimiser clearly marked as made in China on unit whereas the Enphase is USA or German.

i have an SMA inverter on my own roof and when it fails I will be upgrading my system to Enphase for the warranty and better performance.
 
Enphase swopped the squirrel eaten inverter cable with a complete new inverter within one day and paid us £125 to fit it.

With SMA and Solaredge you need to find a suitable cool space for the inverter which in my opinion should not be a loft space.
 
We are open minded and will design the best system case by case, some installers are particularly pro one technology or another. - Still need answers to the questions I posed of the OP before I'll comment.

Micro-inverters have issues with start up voltages, string Inverters usually have a maximum of two MPP trackers.

Optimisers and Micro-inverters are 'at panel' technology meaning that in a domestic on-roof installation, there will be significant costs in fixing faults. £125 doesn't get a scaffold / tower plus a person on site, it will cost more than that to replace a faulty one. In ground mount or flat roof / elevated installations, the access costs are no different between the technology types.

We do not install string inverters in lofts except as last resort :)
 
I understand that Solaredge and standard string systems may have a start up issue with having to achieve a higher DC voltage from multiple modules but an Enphase inverter is stand alone once there is 5 watts of light.
Enphase systems start earlier and finish later than combined module systems which we can prove as we have a 4000TL East West split system at home with Sanyo HIT modules. Our Enphase systems that we can access on line are up and running a long long time before mine.

The £125 was a good will gesture, the normal swop out fee is a lot more however I agree that if you need scaffold it's probably not enough. The same applies to replacement DC optimiser units from Solaredge as well.

The Solaredge main inverter only comes with a 12 year warranty and needs additional payment to get to 20/25 years.
 
5 watts is low light, not necessarily shading.

What's the minimum start up voltage for the enphase unit?

That is the significant factor with micro-inverters and shading, as string inverters are not so affected by one bypass diode kicking in on a panel. Most micro-inverters start up voltage is greater than that output by a panel when it's lost 1/3 of it's Voc when the bypass diode has kicked in.
 
Sorry it's a cut and paste :

Enphase Energy sets itself apart from any other inverter on the market with the M215’s exceptional low voltage performance. The unit maintains its high level of efficiency even as panel input voltage drops below 20 percent, greatly improving low light performance. Its direct current input peak power ranges from 22 to 36 volts, yet the unit has been tested to perform well at input voltages as low as 16 volts and up to a maximum of 45 volts.
 
8 Sanyo HIT 240 East and West to an SMA 4000TL inverter.
Installed June 2011, at 43p rate, done over 12,700 kW hours so far.

Before that we had a 3.6 kW system which I think was 10 Moser Baer 180 modules East and West with a SMA 1700 for each side. This was fitted in late 2008/early 2009 and was my original MCS test case project. Decommissioned it when we saw the better performance our customers were getting with Sanyo.

So currently waiting for Enphase to release the next generation of micros which we can pair HIT modules and with 72 cell modules, been told they are on test and will be available by Spring 2015.
 
This is just an opinion and I respect your expertise, but I would have used a smaller inverter on an east/west split...
 
There were not that many inverter choices available that were twin tracker in the early days of solar.
The SMA3600 came along later.

As an East West split this system averages over 3600 kW hours of generation a year with the top modules and inverter available at that time.
With respect I do not expect many E/W splits in the UK have generated a lot more !
 
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MCS Renewables said:
There were not that manyinstalled one if inverter choices available that were twin tracker in the early days of solar.
The SMA3600 came along later.

As an East West split this system averages over 3600 kW hours of generation a year with the top modules and inverter available at that time.
With respect I do not expect many E/W splits in the UK have generated a lot more !
Click to expand...

All fair comments, out of curiosity what does your system "peak" at, and how often?
The 3600tl was a long time coming but you would have installed one if it was available at the time and even though your system has performed excellently do you believe it could be better still with the 3600tl?
 
Few months back I wrote to all the folks we had sent out quotes to over the last year that had not bought. I was more interested in the reasons they did not buy. This is what I got back.

10% did not buy because they might be moving house
11% did not buy because one party did not want to. Mainly because of the look.
40% did not buy because they just did not want to spend the money
39% did not buy because they said their brains were fried and were suffering information overload. Some said they were turned against solar because of all the conflicting advice they received from all the companies they got in.

Reading threads like this I know what they mean. Its so difficult for consumers to find advice on one product that another company will dispute.
 
Debate is good :)
 
MCS Renewables said:
There were not that many inverter choices available that were twin tracker in the early days of solar.
The SMA3600 came along later.

As an East West split this system averages over 3600 kW hours of generation a year with the top modules and inverter available at that time.
With respect I do not expect many E/W splits in the UK have generated a lot more !
Click to expand...
fair play, but then you are in dorset, so have a wee bit of an advantage;)

we've got a few similar 4000TL installs out there from 2011 when we were a bit more SMA biased, I think power-one actually had some smaller twin trackers even then.
 
truth of the matter with enphase vs solar edge is that there are pros and cons to both options, they will both probably be within a whisker of each other on generation in most cases, so it's probably more important to sus out the quality of each installer - ask to be put in touch with a previous customer locally to see what they thought of them.
 
Gavin A said:
truth of the matter with enphase vs solar edge is that there are pros and cons to both options, they will both probably be within a whisker of each other on generation in most cases, so it's probably more important to sus out the quality of each installer - ask to be put in touch with a previous customer locally to see what they thought of them.
Click to expand...

Precisely my expectation. Installer quality is far more important.
 
i would agree with solar city hands down the quality of installation is key, I personally dont like enphase and i can see faults occurring through there rubbish trunk cable which to me is low qaulity and will not stand the test, plus with a lot more components behind each panel there is more to go wrong on the roof. gOING TO A SOLAR EDGE meeting to mo in durham should be interesting
 
Enphase predict a 10% share in the inverter market by the end of this year. There latest inverter is 4th generation, so has been around a long while. They also state that the first problem will occur within the first 5 years, after 5 years the inverters will work for another 15 year.
I have fitted a few Enphase systems and its surprising to see how the panels are mismatched due to the positive tolerance.
 
jason121 said:
There latest inverter is 4th generation, so has been around a long while.
Click to expand...

4th Gen - already !!!! How long have enphase been in the market place? 3 years?

jason121 said:
They also state that the first problem will occur within the first 5 years, after 5 years the inverters will work for another 15 year.
Click to expand...

So whose going to pay to fix all those systems???

jason121 said:
its surprising to see how the panels are mismatched due to the positive tolerance.
Click to expand...

Which is nicely sorted by a well designed string inverter.

Don't get me wrong, I have a lot of time for the opinions of the regular contributors to this forum.

It does seem though that some are being swayed by the marketing guys.

Simple:
String inverters work - we all know that and some are more efficient than others. If they go wrong they are quick, simple and inexpensive to swap with regular 10 year warranties.

Micro-inverters (enphase, power-one, sma, enecsys) work, so do optimsers. If they go wrong though when installed on domestic roofs, the replacement costs are horrendous, even allowing for a £125 kick back from enphase. - Are you going to ask all your customers to pay up in say only 6 months / 18 months / 60 months time when one goes wrong (It's not workmanship on your part so not covered by your warranty...) - What are your customers going to say / think?


We all acknowledge that a well designed string array system can perform well, and that micro-inverters / optimisers allow you to install in less than ideal situations.

In which case should you not install? .... whose interests are you serving by installing a system in less than ideal circumstances that has a greater likely hood of costly repairs / maintenance.

What are the real lifetime costs then of a string inverter system vs an 'on-panel' system including replacement and maintenance costs?

Unless there is a significant difference then the argument for on-panel technology doesn't stack up.
 
Fair comments, can't help but agree to be honest. Both solutions have their place but rarely are they a better option where a decent string inverter solution can already be effective
 
Enphase been around a while. They are American company. You can argue the case all day regarding warranties. A few months back I had a problem with a CL48 inverter. Called there technical dept telling me to do this and that to find fault. Eventually I found fault on my own, by pulling out all the power racks. One had burnt connection. Not being a registered Fronius partner I ask for free training because I had saved them a engineers time. The reply was don't do freebies. Sent me a cheque for £60 for my trouble after 2 days fault finding.
 
a bit more detail on the Enphase design reliability as I drilled down into this with them a while back.

IIRC they work on around a 0.2% failure rate per unit, which works out at around a 3.2% failure rate for one unit on a 16 panel array inside the first five years guarantee period when they'll pay towards the actual costs of replacement.

They work on the basis that the vast majority of faults should show up inside the first 5 years, so don't expect many failures inside the longer guarantee period.

They also reckon the actual design life of the units should be in the region of 50 years once any faults have worked their way out in the first few years due to the solid state nature of the units or something. Personally I suspect there could well be a weak link in the chain there such as the communications devices that might cause an earlier failure than for just the inverter side of things itself, but that's just my sods law suspicion rather than based on any data.

They undoubtedly are excellent bits of kit, we just struggle to justify them against the high end string inverters, and I find some of their performance claims vs string inverters to be highly dubious.

Oddly, I suspect that they will have the most impact when used in conjunction with cheaper panels, as they tend to have wider panel tolerances, so one panel could be 10Wp difference from the best to worst performing panels in a set, where s string inverter would operate at the lowest panel output, the microinverters would optimise each panel. Less of an issue where the panel tolerances around more like 2-4Wp from highest to lowest panel.
 
We offer customers both options ( SMA or Enphase ) where applicable and the price difference is only about £1000.

A lot of customers are choosing the Enphase despite the extra cost as they like the information accessibility and the warranty and do not have to give up space in the home for the inverter. They like the ability to log on with their phones and tablets worldwide and are not limited to the 100m sunny beam range!

We have hundreds of SMA systems which do very well but if one of those customers has a problem we are only made aware of it if or when the customer notices.

With our Enphase systems we can log in every day and instantly see the status of each module and inverter on every project in real time and historically.

When the SMA's with five year warranties start failing these customers will have to pay for replacement inverters and the £1000 will soon be eaten up especially if it happens twice. A lot of our customers are on the 25 year FIT contracts so a five year warranty could result in four inverters, although this seems unlikely.

So the replacement "cost" issue is not actually so different.
With the SMA you would have a cheaper labour cost but much higher inverter cost.
With the Enphase you would have a free replacement inverter but may need to use a tower and the swop out would take longer. Only in very extreme cases can I see that you would ever need an expensive fixed scaffolding.

With the Enphase you do have the advantage of knowing exactly which inverter and it's roof position you are replacing in advance and the PV system is still working until the day you undertake the works, which minimises generation losses. With the string inverter you may have a grumpy customer chasing you as they lost a week or so's worth of entire generation until you sourced a replacement and booked some swop out time.

Another consideration is module failure. With the Enphase system you can see immediately which module is underperforming or has failed but with the string inverter you have no chance it wil be a case of testing each individual module in that string, which could be very time consuming.

With regard to performance the Enphase system outperforms the string inverter by 15% according to the side by side test performed by Enphase up North.

I DO NOT consider that this was an ideal test and it is flawed in some respects however if we ONLY use 5% as a fairer figure, over the twenty years that represents an extra ONE year of generation and import kW hour savings for each system. That alone on a four kW system could be worth the £1000 with index linking and future import price rises avoided.

If the Enphase better performance is actually 10% or indeed 15% better over 20 years that is a considerable amount of additional FIT monies and import saving.

SMA obviously think micro inverters are the future and a viable option that's why they are releasing their own version later this year.

Then there is the safety issue of no DC cables or high voltages in the home, if an inverter catches fire it's better outside on your roof than under it, if you have a non PV fire the fireman only have <50v to deal with on the roof when the 240v is isolated.

You can add to the Enphase system at any point by extending the trunk cable without having to resize the original string inverter so that gives some flexibility.

So even on perfectly South roofs with absolutely no shading a lot of customers are choosing to fit Enphase systems because the initial £1000 extra is only a very small part of the overall picture.

There seems to be a lot of miss information about the Enphase system, the communication device has no bearing on the system and cannot interrupt generation, you do not actually need the envoy unit so it can be taken away from site although this does impact on the internet accessibility ! We have done this on several new build sites, four modules with Enphase on each property set them up and take the envoy. This is much much cheaper and easier than any string inverter for this size system. Plus we can always sell the home buyers an envoy and easy system upgrade later!!

If the envoy communication unit fails the Enphase PV systems keeps working which may not be the case with the Solaredge system ?
 
It is the lack of independent empirical data that makes realistic appraisal difficult for both customer and installer.

I understand the National Solar Centre are doing some side by side testing, but I have no knowledge if string vs micro vs optimiser is one of them. Producing identical shade environments for each array could also be tricky.

It is likely that this is very much horses for courses. It is difficult as an installer to wholeheartedly recommend something you can't be sure provides the incremental benefits claimed by the manufacturer. The claims for Enphase and Solar Edge are very seductive. On a 4kW system the incremental cost of Enphase is double that of Solar Edge.

The one small Enphase installation we undertook, (6 x 265w panels) where there were multiple shading objects, has outstripped the performance prediction. (sorry, it is not on line as customer has got rid of internet!!!).

Running Solar Edge through PVSol shows a good gain in an East West installation over a dual MPPT string inverter. I haven't had time to do the same with Enphase. I would conclude that in some circumstances, their use is of benefit, but not in all.
 
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I've got a system of 14 panels, each with their own Enecsys micro-inverter, I've just found out the hidden costs of on panel set-ups. These are configured as 1 set of 5, 2 sets of 4 and 1 on it's own, basically a string inverter in this setup simply wouldn't work. So far to date the system has outstripped all generation predictions significantly and on the whole I'm very pleased with the output, especially considering the number of shading issues the panel has to deal with.

One of my panels started producing considerably less than the other nearby panels, so I contact my installer, this is around 22 months after the system was installed. First reaction is send out an electrician (callout £60) to determine the panel isn't the problem, then contact Enecsys, it appears to be a software fault, this may or may not be fixed over the air, if not, then a replacement will be sent, and another callout fee for the electrician, so roughly £120 or around 15% of the annual income from the panels.

Fortunately for me the faulty unit is on a single story flat roof with plenty of space, so no need for scaffolding, otherwise we're looking at an additional £100-200 for that.

The cost of this shows that if it happens you can extend the payback period considerably, and if it happened towards the end of the life of the system it might be better to ignore the failure and reduce the output of the system, rather than pay for the replacement.

I suppose the flip side is that you can ignore the problem on a single panel if more cost effective to do so, not an option if you have a string inverter. I just hope this is a single one of failure and I can look forward to no more for the majority of the system life.

mike
 
Didn't the installer offer a warranty on their work?

"I suppose the flip side is that you can ignore the problem on a single panel if more cost effective to do so, not an option if you have a string inverter."

Maybe, but panel failure is incredibly unlikely. If ever you're going to have a problem on your roof, it will be from a micro-inverter/optimiser. Not a problem as long as the installer/manufacturer is prepared to support them.
 
SolarCity said:
Didn't the installer offer a warranty on their work?

"I suppose the flip side is that you can ignore the problem on a single panel if more cost effective to do so, not an option if you have a string inverter."

Maybe, but panel failure is incredibly unlikely. If ever you're going to have a problem on your roof, it will be from a micro-inverter/optimiser. Not a problem as long as the installer/manufacturer is prepared to support them.
Click to expand...

It is warrantied, against poor workmanship, which I guess if there's a software fault on an Enecsys inverter it would be difficult to claim it was the installer's fault - I'm not happy about this reaction but can't really see how I can do anything else (the call out was for a 5 minute visit, so hardly justifying the £60 fee). I'm going to try and get something from Enecsys, but am not holding my breath.

What I meant on the single panel failure, if I had an inverter fail on the higher roof mounted panels, thus knocking out a single panel, it would cost in the region of £200 in today's money to install the inverter replacement before the cost of the inverter was considered, so you're probably looking at a cost of at least £300 to replace, if you're in the last year or two of the FITS scheme, it's doubtful whether it would be worth spending the money.

mike
 
mbuckhurst said:
if you're in the last year or two of the FITS scheme, it's doubtful whether it would be worth spending the money.
Click to expand...

Yes it will be - how much do you think 'leccy is going to cost in 18-23 years time :)
 
Worcester said:
Yes it will be - how much do you think 'leccy is going to cost in 18-23 years time :)
Click to expand...

That's a very interesting question, so I did some maths, from a government source (probably about as reliable as a Bernie Ecclestone testimony), it seems the annual average price rise between 2004 and 2011, works out at 15% per year, this means my faulty panel would generate around £400 of electricity for it's final year if this trend was constant and continued for the next 23 years.

I estimate the current cost of repairing a single inverter, on my more inaccessible parts of the roof at around £300 today, so factor in a small inflationary rise over the period would mean that it would actually be worthwhile getting it repaired so long as I could expect 16-18 months of further generation from the panel at whatever time, even if FITS was no longer paid, just so long as I use or get paid for 100% of the electricity

This of course doesn't take into account FITS, but at a guess this would significantly shorten the period required to generate pay back for the repair.

So there you have it, you're correct it probably would be worthwhile repairing no matter what time it happened.

mike
 
Here is an option suggested to me recently by someone who should know:

Use micro inverters for those panels affected by shade and a string inverter for those not. Interesting idea in the right circumstances.
 
MCS Renewables said:
Enphase outperforms Solareddge according to the ONLY independent test results available from PV evolution labs at :- dated Sept 2013 so very current.
http://www.metgen.co.uk/assets/download/index/assets/122/

There are three U tube videos available here about why Enphase is better
Enphase Inverters | Solar PV & Renewable Energy Trade Supplier | Metgen, UK
Click to expand...

It is interesting to read that you found a review in which Enphase outperforms SolarEdge. I found two recent reviews that show the opposite.
One is by the US NREL-institute, also from 2013.
SOLAREDGE POWER OPTIMIZED INVERTER SYSTEM OUTPERFORMS STRING AND MICRO INVERTERS IN NREL-DESIGNED INDEPENDENT TESTING | AltEnergyMag Press Release

The other one is by the German Photon test-laboratory also from 2013. I haven't got this link available at the moment, but I will look it up.

This is important to me since both products (Enphase and SolarEdge) are hot in the market.
Especially because the warranty on the central inverter of SolarEdge can be extended to 25 years and then the their offer is considerably cheaper than Enphase.

SolarPro
Netherlands
 

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