Solar Installer Shuns String Inverters, Switches To Microinverters

Enphase microinverter - Penrith Solar

Penrith Solar Centre managing director Jake Warner with an Enphase microinverter

Citing safety, simplicity, support and performance reasons, NSW’s Penrith Solar has bid farewell to string inverters and is now only installing solar power systems with microinverters.

A solar inverter is the real workhorse of a solar power system – all the electricity generated by the system’s solar panels is routed through this device that operates in often harsh conditions. It’s the component most likely to fail first in a solar power system and this is why special attention should be paid to inverter selection.

Most inverters installed in Australia for home solar installations are string inverters – named so as strings of solar panels connect to them; usually one per system installation. An alternative is the microinverter, which is around the size of a paperback book. One is used with each solar panel, installed on the mounting system rail beneath it. “AC solar panels” have the microinverter integrated on the back of the panel at the factory.

Among the advantages of microinverters is they optimise each panel individually. In a string inverter situation, one shaded solar panel can cause a drop in performance of all panels in that string. Using microinverters, only the shaded panel’s performance is affected.

Another benefit is microinverters convert DC power at the point of generation – the panel – into AC power, meaning high-voltage DC cables don’t need to be run through the roof, plus they don’t require rooftop DC isolators1. Their use also allows for monitoring of each solar panel’s performance.

The Decision To Switch To Microinverters

Penrith Solar Centre services the Western Sydney and Blue Mountains region. After a review of operations the company decided to ditch string inverters altogether and use Enphase microinverters exclusively, which is the leader in the technology.

Among various reasons the decision was made, Penrith Solar Centre founder and managing director Jake Warner says he discovered after going through in-house records that microinverters were eight times less likely to fail than string inverters – meaning eight times less costly to support.

Mr. Warner says due to their small size, microinverters are also easier to store, transport and install. Additionally, it makes inventory control much simpler.

“We’ve already ordered 7500 microinverters for quarter two this year,” he said. “If I was ordering string inverters, I would have to break that down into 5 kilowatt (kW), 6kW, 7kW, 8kW, 10kW, 12kW and 15kW inverters whereas now I literally order just one microinverter for each solar panel on order.

Mr. Warner noted other major benefits of their use include better performance in hotter conditions, simplifying system design and improved remote diagnosis of system issues.

Value Vs. Cost

There’s a lot to like about microinverters, but one of the disadvantages is they will add 20 – 25% on to the cost of a solar power system installation. But Mr. Warner says:

“The reality is that if string inverters and microinverters were exactly the same price, no one would ever buy a string inverter.”

String inverter manufacturers might have a bit to say about that, but microinverters are worth considering particularly if you have a partial shading scenario and/or your budget allows. Another option is the use of power optimisers, which still require a string inverter installation.

Related: learn more about panel level optimisation (PLO).

Footnotes

  1. Hopefully rooftop DC isolators will go the way of the dodo soon anyway. Find out more in episode 3 of SolarQuotes TV
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. John Swenson Harvey says

    One other advantage of microinveters is they typically have twice the (warrantied) life of string inverters. So once one factors in replacing the string inverter at least once during the system’s life the (expected) life time cost difference for the two types of systems becomes much smaller, possibly zero.

    I have a 7,650 Watt system that was installed in May 2013 (30 panels 30 Enphase M215 microinverters) and have had zero production issues. I have access to daily production records for each panel, and have seen essentially zero reduction in output after the first week of operation. 2020 was my highest production calendar year ever. I’m closing in on 100 MWh of production (98.5 MWh as of April 14, 2020). The system’s output can be observed at: https://enlighten.enphaseenergy.com/public/systems/nprh192552 or https://pvoutput.org/list.jsp?id=22322&sid=20215

    • US gets 25yr warranty.
      AU gets 10yr standard, 15yr if installed by a Platinum installer, or 20-25yr if you wanna pay morez again.

  2. I wasn’t aware that micro-inverters were available seperately to the panels.
    Does this mean a system with 1 string inverter could be retro-fitted with micro-inverters, especially if the string inverter has failed?
    I have shading of some of my panels (due to neighbour’s trees growing) and micro-inverters would (I feel) help.

    • Ronald Brakels says

      Jeff, that can be done, but I recommend considering getting an entirely new system as you may find having a brand new and potentially larger solar system with a set of new warranties worthwhile.

      Another option would be to place optimizers on the affected panels. These can used used with a normal string inverter and provide similar benefits to microinverters.

    • Marty Lacis says

      Highly likely, on both counts.
      Check for module compatibility here if specs. are known:
      https://enphase.com/en-au/content/module-compatibility-calculator-en-au
      However, always check with a solar PV pro.

  3. Marty Lacis says

    As a recently expanded 15mth NSW Enphase, predominantly positive, system owner, 2 things have moderately soured the aforementioned positives: firmware & firmware.
    Various microinverter version updates have variably introduced totally random zero or reduced periods of panel production output compared to those adjacent, & the lone Envoy update removed entirely the Estimated Curtailment reporting leaving me less Enlightened.
    Bring forth a ‘Revert To Previous Version’ button!
    https://enlighten.enphaseenergy.com/public/systems/fEfv1682494
    https://pvoutput.org/aggregate.jsp?id=30437&sid=71097&v=3&t=m

    Regarding the written story, it’s rare a company is willing to forgo likely additional business & income on principle in a competitive solar PV market.

  4. Se tensão é causa, não é efeito, então evito micro-inversores e mudo para inversores com fator de entrada de paineis solares 1.96 a 2 em relação a potencia do inversor. Sendo assim gero mais energia KWh do que micro inversores. Exemplo; Inversor GE 7KW 220v x 1.96 / 41v= 10 x 3= 30 x 450w= 13.5KW painéis solares contra 7kw micro-inversores.

    • Ronald Brakels says

      Não é uma má ideia, mas não é possível para uma instalação normal na Austrália.

      (Not a bad idea, but not possible for a normal installation in Australia.)

  5. Sometimes, I wonder if I erred going down the Fronius + Full optimisers route instead of Enphase.

    On the other hand, I did spec my system to be very resilient.

  6. Robyn Parker says

    Most of the reasons stated for ditching string inverters are things that benefit the company, not necessarily the consumer. This doesn’t really demonstrate that string inverters are going the way of the dodo because they are better, just that its cheaper and more efficient for the company providing the service.

    Given the increased cost i find this worrying. I think people will be mislead that this company is selling only micro’s because they are “better” – not realising that better means better for the sellers bottom line, not better for the purchaser.

    I say this as someone who has been sold a micro inverter system, when i suspect that a cheaper string would have done the job just as well. My impression was that the install was considerably easier so I ended up paying for a more expensive system to save the installer time and money. Beware.

  7. is there any value installing second hand panels with micro inverters for a stand alone system

  8. After having three inverters fail, we decided microinverters were a better idea – if one fails, production from only one panel is affected.

  9. Giancarlo Buffon says

    What about batteries? It doesn’t look like a system that could support a battery connection?

    I’m worried in time the governments will start making having solar an issue, as they will just keep reducing the returns you can get from feeding power out, and the only way save money is to have no (or very little) draw from the main power network using batteries.

    • I have a system of 24 x 320W SunPower panels with Enphase microinverters and a Tesla Powerwall2 battery. They work together very well. During power outages the battery powers my house and if it’s a sunny day the battery is charged simultaneously.

  10. Leanne Hampshire says

    Hi, I am considering Maxeon (Sunpower) panels but Rimfire Energy here in Darwin said microinverters were not ideal in our harsh tropical climate. While their recommended panels and string inverter are great quality products I was keen to go with microinverters. Does anyone have any postive or negative experience of micoinverters in the tropics? Heavy rains, wind and hot days?
    Leanne

    • Ben Steenson says

      We live in Darwin and have 20 Sunpower E20 /327 watt panels with Optimers on each panel with SE5000H inverter. Gem Energy install this 3 years ago and has been awesome to date. The software monitoring is easy to understand and all comes with 25 year warranty.
      Regards
      Ben

      • Leanne Hampshire says

        Thanks for the feedback Ben. Rimfire said they can install anything I want but were hesitant to go with microinverters. At the moment I think Rimfire is still offering a 1 for 1 feed in tariff so I am keen to go with them.

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