I recently received this advice from a supplier I asked for a quote for my situation in a shaded area, regarding Optimisers Vs Micro inverters. reply is as follows:
Using an inverter technology like SolarEdge with optimisers behind every panel, or even using a string inverter like a Fronius with TIGO optimisers behind every panel, still have a weakness when compared to Micro inverters. Optimisers work well when some of the panels are shaded, but in order to continue functioning, they always need at least 6 panels to be receiving sunlight… If most of the array is shaded, and there are only 4 or 5 panels left receiving sunlight, these optimised systems will not function. With micro inverters on the other hand, you could have every single panel shaded except for just 1, and that 1 panel will still keep pumping out its full power completely unaffected by all the other shaded panels.
So, for moderate/partial shading, I would have recommended SolarEdge optimisers, but because you roof is subject to even heavier shading at times, Micro inverters are the better choice long term.
UPDATE - Tigo seems to have an advantage over SolarEdge in this heavy shading scenario.
I believe what he is saying is accurate. I haven’t used optimisers before, but I understand that it is true regarding needing a number of panels to produce power for the inverter to function.
I guess the logic that if you have heavy shading then you should use micros is probably fair also. Although, if your shading is that bad, are you sure you’ll get enough sunlight for solar to be worthwhile? Is the supplier able to give you an idea of the output of the system, and what impact the shade will have?
Can anyone give more information about the pros and cons of micro inverters vs optimisers? This has come up quite a bit recently, and I’m not confident I have all the facts. This is a little old news, but I have just been reading that SMA has partnered up with Tigo to produce a “smart module”, and is integrated into the Sunny Design software.
Correct me if I’m wrong, but it sounds like Tigo optimisers can be used with any inverter brand, whilst SolarEdge optimisers are only compatible with SolarEdge inverters. Are the SolarEdge optimisers superior in any way? Otherwise it sounds like Tigo has a bit advantage in being compatible with all inverter brands.
Also, as the OP mentioned, optimisers seem that they would have an issue in heavy shading when the inverter does not receive enough voltage to function. Is that a real concern, and if so, is that the only disadvantage of a power optimiser over the micros?
Lastly, what about price? Is Tigo the most cost effective out of these options?
For reference, we’ve got a couple articles on SolarEdge and Enphase, but not much on how they compare, and where Tigo fits in.
I cannot speak to the comparison of Solar Edge to Enphase (solar edge not available in my area). However, I can speak to the comps. of Enphase and Tigo. I like to make a list for comparing.
Tigo works in conjunction with a string inverter. Enphase is the inverter.
Tigo works with most panels either with a direct change of the panel box or with an adapter kit. Enphase works with all panels that have a standard DC line interface.
Tigo sends power from the panel to the inverter in the form of DC power. Enphase converts the power directly at the panel and sends AC power to the home.
Tigo optimizers separate the panels so they are unaffected by other panels in the string. Enphase separates each panel so it is its own string.
Tigo is still dependent on the central inverter for power conversion - inverter fails, entire system shuts down. Enphase micro-inverters are the individual inverter on a per panel basis. A micro-inverter fails, one panel is affected. The rest of the system remains in operation.
Tigo does not convert the power, this is dependent on the string inverter. Enphase is the inverter, however each is restricted to a maximum power output regardless of the size of the panel. The IQ7 will allow a maximum 250-watt throughput (60 cell panels) and the IQ7+ will allow a maximum 295-watt throughput (72 cell panels). While this sounds like it would be an advantage for Tigo, other inherent problems with string inverters cancel this advantage.
Tigo is dependent on the string inverter for startup power restrictions. Enphase has very low per panel requirements for initial operation parameters.
String inverters with Tigo optimizers will peak at a higher power output than Enphase, However, Enphase consistently yields higher overall average production.
The real test is in head to head comparison. During our change over period from string inverters to Enphase, we had occasions where it was more beneficial to install a string inverter with the Tigo optimisers in place of the Enphase M250 micro-inverters. Had the client come to us even 6 months later, there would have been no choice. In every case we have installed string inverters with optimisers the IQ eries including the IQ6, 6+, 7 and 7+ are out performing the string systems. This is with (in some cases) exactly the same size panels, installed in the same geographic area. Because we are on Yucatan’s coast we do not have to deal with shading issues (at least not often) and with flat concrete roofs we do not have to deal with slope issues. We get perfect southern angles and can compare the two systems easily. Enphase IQ series outperforms every other system we have installed or been asked to work on.
One other note. We have a twitchy grid - Mexico 127 volt and it is old. We experience constant fluctuations in power delivery. In many cases these fluctuations knock the string inverters offline. However, the Enphase generally remain in operation (unless we get really crazy high fluctuations and this happens far more often that we would like).
Just wanted to follow up. Had the opportunity today to check one of our string inverter systems with Tigo optimisers. This is a 16 panel system using 340-watt panels connected to Tigo optimisers on 2 MPPT fed into a Kaco 5kw string inverter. Maximum production of this system is running at 31 KW on the best days, most days around 25 - 27 KW. No shade issues Southern Exposure panel angle 3 degrees (the advantages of a flat roof and no obstructions). In comparison we have a number of 12 panel systems (same area, same conditions, same panel angle) using Enphase IQ7+ micro-inverters and 375-watt panels. Total calculated potential output - 16 panels - 5440 watts, 12 panels 4,500 watts. Peak production - string inverter (daily output) 31 kilowatts. Peak production - micro-inverters (daily output) 30 kilowatts. Average daily output - String inverter - 24 - 25 kilowatts. Average daily output micro-inverters - 25.5 kilowatts. Remember these are micro-inverter systems that are 940 total watts smaller than the string system (with optimisers) and they are averaging the same or higher daily output.
In one sentence “SolarEdge is crap with a good name”. They’re not forward or backward compatible (biggest issue) you can’t have any less than 8 panels in a string or they won’t turn on the main inverter (less than 14 panels in a string you cop a hit on performance). If you need to add to a system 3 yrs old (give up) you run into all sorts of hassles, rip it off the roof and start again. All the scam artist door to door guys push them with crap panels. I spend at least 3hrs a week doing warranty work on new SolarEdge systems installed by other larger solar companies, I won’t mention any names here. Most of this is comms related, or dodgy optimizers (these are newly installed systems like 1 month HD wave). Tigo’s are good optimizers (and yes they work with any panel or Inverter) I use them often for partial deployment on my Fronius systems, 3 or 4 panels. SolarEdge will only talk to the right model of SolarEdge. If you wanted a fully optimized system with panel-level monitoring Tigo is far too expensive. Better system less cost ENPHASE. Not to mention they make string inverters look stupid when it comes to total energy harvest. Mind you I do have a Fronius in my shed lol. (OHHH!!! if I had the knowledge then that I have now LOL) “anyway” going cheap 5.27kW Trina Duomax (glass on glass frameless) Fronius 5.0.1 less than 2 years old . I’d go to LG/Enphase any day.
Thanks @Den_Thomson, gee you guys are really pumping up Enphase. What I’m surprised about is that Anthony is saying that the micros perform considerably better in perfect conditions. I would usually suggest micros for shaded installs, but I guess you’re saying that if you can afford the upfront cost, you’ll get the rewards over the lifetime of the system even where shade is not an issue.
The evidence is there 2 brand new systems lets say, Lg NeOn2 330w 20 panels 6.6Kw side by side ground mount optimal conditions. One with Fronius string the other Enthase IQ7+ proven 12% more energy harvest. I tell my customers 6% because I always err on the side of caution.
OMG Den, could we be brothers from different mothers. Started Emerald Coast Solar (on the Yucatan Coast of Mexico) 4 years ago. Have been having exactly the same issues with the competition and have come to the same realization with regards to Enphase. Currently have both a Kaco string unit with 14 panels (first install I ever did) and an Enphase M250 system with 6 panels. Will soon be ripping the Kaco off the wall and converting the existing panels to use the IQ7 micros. If I knew then what I know now…
This discussion has been very informative. I’m not an installer, just a homeowner thinking about a solar carport rather than a house roof install. It looks like shading would suggest micro inverters but I have a couple of other questions. Do micro inverters preclude a grid-tie system that will operate during an outage or otherwise complicate the use of backup batteries, and what if charging an electric vehicle is added to the plan in future? Thanks for all your good comments.
Interesting discussion re Tigo V Enphase V Solar Edge. If SolarEdge require at least 6 panels to be receiving sunlight, they probably work well when there are enough panels. I’ve heard SolarEdge installations can result in problems when the installers don’t read the instructions and install them like Fronious
Currently, the EnPhase Microinverters, iQ6 and iQ7 can’t provide power during an outage, and any battery storage would have to be AC coupled. So even the battery goes offline in a power outage. But the new iQ8 coming soon will be able to form a micro grid during an outage. For this to work, you also need the soon to come EnPower MID (Microgrid Interconnect Device) which will isolate your system from the main grid so it can power up your house without feeding out to the grid. By adding the EnCharge-3 or EnCharge-10 battery units, the system also will store power and can provide power at night. The new iQ8 based solar panel inverters and EnCharge batteries will be compatible with the current iQ6 and iQ7 inverters, but with a few limitations. There will need to be at least one iQ8 for every iQ6 or 7 in the system, for it to be able to form a grid and keep the output stable. The EnCharge-3 battery will have 4 iQ8’s inside, and I think the EnCharge-10 will have something like 12 iQ8’s. I will be adding at least an EnCharge to my iQ7 system when they become available. Thanks to Time of Use rates, I need to shift some of my solar generated power to after 5 pm. To be able to run backup without the grid, I would need at least 2 of the EnCharge-3’s and also have to change 4 of my panels from iQ7 to iQ8 to get the 1 to 1 iQ7 to iQ8 ratio needed.