Is Solar Panel Optimisation Worth It?

Solar string inverters, micro-inverters and power optimizers. What’s the best choice? Finn offers his point of view in this video (transcript included).

Transcript begins :-

There are three main components in a solar PV system – the panels, the racking/mounting, and the inverter. This video focuses on the inverter, whose job it is to convert the DC electricity generated by the panels into AC electricity that is used by your home.

Inverter Choices

Now, you’ve got three choices when it comes to inverters.

  • String inverters
  • micro-inverters
  • and optimiser based systems; which are kind of a hybrid between string and microinverter technology.

If you’ve got a short attention span, here’s my hot take. Microinverters and optimizer based systems are more expensive than simple string inverters, but they have a variety of benefits that make them worth considering; especially if you have a shaded roof.

Now, let’s go into details.

String Inverters

String inverters are roughly the size of a briefcase and they are mounted on a wall. All of the panels connect into them. For residential sized systems, you’ll only need one string inverter per solar system. They operate at high DC voltages, but they’re perfectly safe when installed by a competent licensed solar electrician.

string inverter

String inverter – 1 per solar system

Microinverters

Microinverters on the other hand are the size of small paperback books and they’re installed on the back of each individual panel. So, for say a 6.6 kilowatt system made up of 20 panels, you’ll have 20 micro-inverters along with them.

Microinverters convert DC to AC at the source, meaning there’s no high voltage DC running through your roof at any point in time. It’s all much safer AC electricity instead, and this is why I use microinverters for my own home. Parts of my home are made out of straw bales – seriously – and I didn’t like the idea of high voltage DC running through those straw bales.

In Australia in 2020 as far as I’m concerned, the only game in town when it comes to microinverters is Enphase. (Disclosure: Finn holds Enphase shares).

microinverter

Microinverter – 1 per solar panel

One core advantage of microinverters over string inverters is that it makes every panel independent of each other. So when one panel is shaded, it only affects that panel. In a string system, when one panel is shaded, the whole string of panels can go down – kind of like when you stand on a hose.

Because micro-inverters have this panel level optimization, you’ll also find that you can get as much as 12% more energy out of a microinverter system over a year compared to a string system. This also means that you can have panels facing every possible direction; whereas with string inverters, you can only choose two, sometimes three directions per inverter.

Optimiser-Based Systems

Now let’s talk about optimizer-based systems, which as I said, are sort of a hybrid between string and microinverters.

In a system that uses optimizers, you have both the big string inverter on the wall as well as individual optimizers on each panel. So, you get essentially most of the same benefits as a microinverter based system, but with a slightly different technology.

Now, for many years SolarEdge was the only real optimizer based system on the market. But, there have been two big entrants to the market that have been challenging SolarEdge’s dominance. They are Tigo optimisers and Maxim integrated panels.

Tigo optimisers work with any inverter; whereas with SolarEdge you have to use a SolarEdge string inverter with the SolarEdge optimizers. And, with Tigo, you don’t need to optimize the entire system like you do with SolarEdge. So if only two of your panels are shaded by say an aerial, then you only need to put a Tigo optimiser on those two panels.

Tigo optimisers

Tigo optimisers – 1 per panel where required

That brings significant cost savings compared to SolarEdge, but bringing even more significant cost savings to the market are Maxim integrated panels. At the time of filming, early 2020, the only brand of Maxim integrated panel that is sold in Australia to the best of my knowledge are the Seraphim MX panels.

Maxim chip solar panel

Seraphim Maxim solar panel

Maxim integrated panels have three tiny chips embedded in the solar panel itself; compared to Tigo or SolarEdge optimisers that are bolted onto the back of the panel. And, these Maxim optimisers bring most of the benefits of other optimisers at a fraction of the cost.

Do You Need Panel Level Optimisation?

Now, do you need this panel level optimization (PLO) at all, or to rephrase, do you need to spend extra money on panel level optimization?

If you have a simple roof with no shading issues, then in my opinion, it’s much harder to justify the extra cost of panel level optimization, but it’s up to you whether it’s worth a few grand. If you have a complicated roof with lots of different faces with or without shading, then PLO is well worth it.

If you have a simple roof with small shading issues, Tigo optimizers will give you the best results for the lowest cost.

Microinverters and Tigo/SolarEdge, but not Maxim, also offer panel level monitoring. Trust me, this gets boring fast, but a small percentage of owners can’t get enough of it – so it may be worth considering being able to monitor the power of each panel individually.

For a deeper dive into panel level optimisation – see this post. For everything you need to know about choosing a solar power system and an installer in Australia, check out Finn’s book, The Good Solar Guide, which is free to read in its entirety online.

About Michael Bloch

Michael caught the solar power bug after purchasing components to cobble together a small off-grid PV system in 2008. He's been reporting on Australian and international solar energy news ever since.

Comments

  1. There was a scientific study performed in 2019 on optimization. In summary, using optimizers on panels that are shaded will provide better performance if moving the affected modules is not possible.

    If installing optimizers on panels that aren’t affected by shade, it actually caused a drop in production. This is important for those certain customers who just want them for the sake of it but can’t offer any real explanation as to why.

    I must also stress, optimizing modules that are shaded shouldn’t be just optional. Most panel manufacturers won’t warrant panels that have failed due to early diode failure from constant shading. This is very common as the attitude from most installers is ‘They’ll just produce less’. This is half true, they will also likely fail prematurely.

    For those interested, the optimization article can be viewed here – https://www.sdu.dk/-/media/files/om_sdu/centre/cie/optimizer+for+pv+modules+ver11_final.pdf

    • Hi Andrew,

      Good points – we covered that study in detail a couple of weeks ago:

      https://www.solarquotes.com.au/blog/panel-optimisers-danish-study/

      Finn

    • Hi Andrew/Finn,

      I will be half my panels on east facing roof and half on west-facing roof. Would this be considered as “shading” on both sets of panels for half a day ? If so, would optimiser based systems or micro-inverter based systems be useful ? Would my panels suffer from “early diode failure” with either of these systems ?

      Regards,
      KP

      • Ronald Brakels says

        Hi KP, Ronald here.

        Your east facing and west facing panels will be on different Multiple Power Point Trackers (MPPT) on your solar inverter. This will allow them to operate independently so they won’t affect each other. Solar installers are not permitted to have panels facing different directions on the same MPPT unless something that will prevent problems is used, such as panel optimisers.

        If, instead of a standard string inverter, your installation will use microinverters each panel will operate independently so there won’t be a problem with them.

  2. John Rockliff says

    Re availability of Maxim panels,
    one of your recommended installers Solar Wholesalers was supplying and installing Wuxi Suntech STP300S-20/Wfw-Mx Maxim built-in optimiser panels as of November 2019.

  3. Les Sketcher says

    I installed 14- 250W panels with micros and Aps monitor in 2014.
    Then 2 Enphase Batt’s and 4 LG 330W panels with Enphase Micros and Enlighten Monitor in 2016. The system has worked to predictions so far except proper cycling of the battery charge for a few months after it was installed. The key point about this is that both installers assured me that they would be monitoring the system after it was installed but neither brought it to notice.

    The value of the monitoring system to me has been to expose the battery charge problem which proved to be a grid voltage out of limits and with the APs
    monitor a good picture of the system performance over the six years of operation.

    I am now considering installing a few more panels to take the system to 6 Kw
    with Iq7 micros as my ‘chief accountant’ has always hounded me about outage back-up. The maxim panels sound interesting.

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