microinverters vs optimizers in real world use questions

[J.P.M.]

It is easy to hypothesize how an optimizer is better than micro because smaller wire can be used until you are on a roof trying to measure the length and EMT bends, LB’s needed. Next cut the piece parts, installing the stuf and then snake wire through it just to save a few bucks using a heavier gage romex and pull it through an attic, Do that and come back and brag how you saved a couple of bucks on wire, Don't bother calculating the time lost plus the added cost for tubing.

An example of how what I wrote in the last sentence of my immediately prior post works in practice.

[foggysail]

It is easy to hypothesize how an optimizer is better than micro because smaller wire can be used until you are on a roof trying to measure the length and EMT bends, LB’s needed. Next cut the piece parts, installing the stuf and then snake wire through it just to save a few bucks using a heavier gage romex and pull it through an attic, Do that and come back and brag how you saved a couple of bucks on wire, Don't bother calculating the time lost plus the added cost for tubing.

EDIT: Optimizers do work! My above merely showed my dislike for the work involved using conduit! JPM’s above post said the same in fewer words—- Just gave JPM a ‘’like!’’

[J.P.M.]

It is sad that a lot of decisions are made based on finances and not quality. But I guess that is the age we live in.

I realize this is about wire gage, materials and voltage, but in a more general sense, quality and decision making, like most everything else, has a price. That price is not always calculated in financial terms.

For example, what's the tradeoff between financial and physical security ? Pay your money, take your choice and make it your best shot by being informed.

Taking the time and making the effort to be informed enough to know the costs and tradeoffs, and so have the information and ability to make intelligent choices is usually the rub.

[SunEagle]

It could even make a difference in the amount of conduit to fabricate, or not. It all depends on where you are standing. I have done both and those are the decisions that will drive the final conclusion, not whether one is better than another.9

It is sad that a lot of decisions are made based on finances and not quality. But I guess that is the age we live in.

[Ampster]

It could even make a difference in the amount of conduit to fabricate, or not. It all depends on where you are standing. I have done both and those are the decisions that will drive the final conclusion, not whether one is better than another.9

[heimdm]

WIth SE you are at 415v vs. Enphase 240v. Depending on the lengths of wire you are running, dividing by 415 v. 240 can make a significant difference on wire size required.

[foggysail]

I have bent enough of that stuff to not look forward to bending, cutting, fishing if there are ways to avoid it. And yes , I still have the tools. My business partner and I did commercial electrical work long enough for me to not look for more of it

[foo1bar]

Not sure outside wiring, it may require SE cable to the disconnect but that is easier to install than metal conduit.

SE cable may be easier than conduit, but conduit isn't that difficult to install. I installed a number of pieces of EMT for my installation. Sure I had at least one that I bent wrong and I had to re-do that 10' piece (and used sections from the screwed up one for other purposes) The tool to bend 3/4 EMT conduit isn't that expensive, and while a beginner may not be able to get as pretty of results (ex. 3 offsets all perfectly matched, all offset to within 1/16" of what they should be), a beginner can make simple bends and can get pre-bent parts like offsets that it will work well.

[foggysail]

Was 100 watts the minimum you've seen? What about at per panel level?



I get that, but I was hoping that people would have noticed or tracked these things. I get that every install is different so there would be variations, but trends would be noticed if people pay attention.



I get the difference between the string and optimizer/microinverter, but I am more interested difference between optimizer and microinverters in the case of low light, or partly snow.

I guess if we go by which vendors, then Enphase vs SolarEdge I guess?

There is a consideration IF you go with optimizers that could be important to you. Optimizers output DC voltages that by code require the wiring to be in metal raceways, metal conduit or metal enclosed wire (MC). Micro's output AC and allow use of a simpler wiring such as using Romex inside. Not sure outside wiring, it may require SE cable to the disconnect but that is easier to install than metal conduit.

[brycenesbitt]

The problem is there is no economic incentive in keeping track of real world performance between the micros and optimizers. No manufacturer is going to admit that they are selling buggy products, they just come out with a new model and hope the price attracts enough installers to blend over the past problems..

There's some hope, if you trust https://pvoutput.org/ data, that real world data
not controlled by the companies could be compared. It would be hard though, as lots of variables exist.

[jflorey2]

I guess if we go by which vendors, then Enphase vs SolarEdge I guess?

Well, the term "optimizers" is not quite correct for Solaredge, since they do more than just optimize power output - they also provide a regulated 400 volts to the inverter. Tigo optimizers, on the other hand, are more of a pure optimizer that just ensure maximum power in a string based system.

An additional complicating factor is that both Solaredge and Enphase make a lot of different products. The Solaredge P370 can run its MPPT tracker starting at 8 volts; the P505 has to get to 12 volts. Compare that to the IQ6-60 which starts up at 27 volts and the IQ8H-240-72 which starts up at 38 volts.

That means that Solaredge wins, right? Not really. As mentioned earlier, open circuit voltage rises quickly to its nominal value when even a fraction of normal sunlight is hitting the panel. That's why you will see close to Voc coming out of the panel whenever its outside even if it is facing away from the sun; the ambient light is enough to get the voltage up there. It is not enough to get any power out of the panel, though, and you might see a few watts max unless the panel is in full sun.

That means that there might be a few watts difference at very low illumination levels, but as soon as the panel is capable of generating any power at all, both systems will be able to generate power at similar levels.

At very low light levels. things like tare loss (how much power the inverter takes to operate itself) and minimum MPPT duty cycle (how low the MPPT converter can operate) are far more important, and are not often spec'd. Tare loss on the Enphase is a minimum of .06 watts at very low light levels, for example, but that is not spec'd for the Solaredge. However, we are talking scenarios where your whole array is generating 10-20 watts before those factors get very important.

As a final comment I would not trust auto-reported values at low power levels unless those measurements were backed up by an actual meter measurement, which is fairly easy to do with a clamp-on meter for both systems.

Personally I have had good luck with both straight string systems and Enphase systems. But with a well installed system, you're just not going to see that much performance difference between Enphase and Solaredge when it comes to energy produced over the course of a year.

[Ampster]

Was 100 watts the minimum you've seen? What about at per panel level?
............

I guess if we go by which vendors, then Enphase vs SolarEdge I guess?

I have seen as little as 3 Watts from an IQ7 micro. I also have a SolarEdge system but it is remote and I do not pay much attention to that detail, I just look at the bill to make sure it is functioning. . It is a toss up for me, since I have have had both Enphase and SolarEdge systems. My current system is a DIY system and I am going to incrementally add capacity on several orientations and that is much easier to do for me with micros. In my current system I have several buildings and some used panels so matching strings is not an issue and running a few micros into a subpanel is easier than a long run of DC. Clearly string inverters scale up more economically which is why any large system is more likely to be a string inverter.

[hsnoil]

I have a system of twenty 345 Watt panels using Enphase micros whose maximum output is 290 Watts. My array orientation is SSE and I saw system output at100 Watts at 6AM and finishing at 100 Watts at about 7PM. The peak output was 5700 Watts at Noon. Because they are micros, I do not have measurements for DC voltage or current.

Was 100 watts the minimum you've seen? What about at per panel level?

The problem is there is no economic incentive in keeping track of real world performance between the micros and optimizers. No manufacturer is going to admit that they are selling buggy products, they just come out with a new model and hope the price attracts enough installers to blend over the past problems..

I get that, but I was hoping that people would have noticed or tracked these things. I get that every install is different so there would be variations, but trends would be noticed if people pay attention.

You are asking the wrong questions here. Those are specific questions about specific hardware. You can get microinverters that operate to lower voltages and you can find optimizers that require higher voltages.

Solar panels tend to put out the same voltage no matter what; the actual voltage depends on temperature, not amount of light. (At least down to very low light levels; below a certain insolation voltage falls off rapidly.) Thus having a low startup voltage doesn't really matter in terms of production, as long as the panel can maintain its max power output within the MPPT (not the startup) voltage range.

Of course the CURRENT changes when light level changes, which is why in partial shading conditions optimizers/microinverters work a bit better.

If all the panels have the same snow coverage then it doesn't much matter whether you have optimizers, microinverters or plain old string inverters. If some panels clear before others you will see a moderate advantage in optimizers/microinverters over bare string inverters.

I get the difference between the string and optimizer/microinverter, but I am more interested difference between optimizer and microinverters in the case of low light, or partly snow.

I guess if we go by which vendors, then Enphase vs SolarEdge I guess?

[jflorey2]

From my understanding, microinverters have a minimum of 16v to operate, but they won't invert until 22v

For optimizers, minimum is 5v, but you need 350v to turn on the inverter? So say you have 35 panels. does that mean that it won't invert until the average is 10v?

What would happen if most of your panels are fully covered in snow with 10 partly covered producing 30v each. Would that mean it won't run?

You are asking the wrong questions here. Those are specific questions about specific hardware. You can get microinverters that operate to lower voltages and you can find optimizers that require higher voltages.

Solar panels tend to put out the same voltage no matter what; the actual voltage depends on temperature, not amount of light. (At least down to very low light levels; below a certain insolation voltage falls off rapidly.) Thus having a low startup voltage doesn't really matter in terms of production, as long as the panel can maintain its max power output within the MPPT (not the startup) voltage range.

Of course the CURRENT changes when light level changes, which is why in partial shading conditions optimizers/microinverters work a bit better.

If all the panels have the same snow coverage then it doesn't much matter whether you have optimizers, microinverters or plain old string inverters. If some panels clear before others you will see a moderate advantage in optimizers/microinverters over bare string inverters.

[solar pete]

The problem is there is no economic incentive in keeping track of real world performance between the micros and optimizers. No manufacturer is going to admit that they are selling buggy products, they just come out with a new model and hope the price attracts enough installers to blend over the past problems..

Aint that the truth, well said sir,