DON’T TRUST THE FRONIUS PRIMO SOLAR INVERTER, make an educated decision. In a sea full of alternative inverter technologies how do you know what you’re investing in for the long-term is the right choice for your home or scenario?

It is true, the Fronius Primo is understood to be a good solar inverter, but why is it so well received amongst installers and consumers alike? Make no mistake, reliability is the key factor. However, how does the Fronius Primo compare when the inverter landscape is now evolving with new consumer expectations such as battery compatibility? Below is the information you must understand before incorporating the Fronius Primo with your solar energy system.

What Fronius inverter do you require? The Fronius Primo is the single phase inverter by Fronius for systems rated at 3kW or above.

  • Single-phase 1 – 3kW, Fronius Galvo >
  • Single-phase 1 – 15kW, Fronius Primo. (You are here)
  • Three-phase, 3 – 20kW, Fronius Symo >
  • Three-phase, 25 – 27kW, Fronius Eco >
How to know if you have a single phase or 3-phase power supply? >


Fronius Symo Solar Inverter Logo - Solar Review

Possessing an extra large voltage window, the Fronius Primo is one of the most versatile transformerless solar inverter designs available and 95% compatible with your solar installation with 1-2 roof orientations max. A common design practice which the Fronius Primo will cope exceptionally well with is solar array oversizing. Just ensure the voltage and current ratings remain within the inverters limits and there will be no detrimental side effects. Now to the interesting part.

Battery Design.

Here’s the good news, you do not need a hybrid (multi mode) inverter to be battery ready. The Fronius Primo is compatible with most leading solar battery technologies already including the world famous Tesla Powerwall 2. Here’s two options without incorporating an additional battery inverter.

Option A 

Battery: Tesla PowerWall 2 (AC Coupled).

Connection: The Tesla Powerwall 2 has an inbuilt 5kW battery inverter with 13 kWh of energy storage contained within the one device. The Tesla Powerwall 2 is wired directly to the same distribution board as the Fronius Primo solar inverter and can monitor the solar production and energy supply (for charge and discharge) with its own communications gateway.

Note: AC coupling will increase a dwellings total inverter capacity, (example: 5kW Fronius Primo + 5kW Tesla PW2 = 10kW total inverter capacity). Certain grid connection parameters in different regions of the world will limit the maximum capacity a dwelling may produce, therefore, this method may not be for all.

Option B 

Battery: SolarWatt Matrix (DC Coupled).

Connection: Beautiful simplicity. One string of the solar array is wired directly into the SolarWatt Matrix BMU (battery management unit). Then from the SolarWatt BMU the Fronius Primo is connected via the DC input. A communications gateway is required at the distribution board for intelligent battery charge and discharge control.

Note: This connection method does not have an option to provide an emergency power supply in the event of a power failure.

Download the Fronius Primo datasheet here:


What we like: The continuation of the LCD display combined with the three light LED notification system as a localised point of reference. Modern inverter designs from alternative major manufacturers have begun to move away from the once popular LCD screen. The main reason, cheaper LCD screens are a common point of failure when subject to a diverse set of environments. The inverter still operates under LCD screen failure, the localised performance and log becomes inaccessible. 

Other notable key features include:

  • Dual MPPTs.
  • Extra broad MPPT voltage window.
  • Dynamic Peak Manager: MPPT shade management.
  • Easy installation.
  • DC isolator built in.
  • WiFi monitoring inbuilt.
  • Remote monitoring.
  • Smart Grid Ready.

For those requiring Galvanic isolation, it is important to not that the Fronius Primo models do not provide this due to the transformerless design. Fronius Galvo models will however provide this feature.


Fronius Primo inverters boast impressive conversion efficiencies. At standard test conditions, Fronius inverter models are capable of a maximum efficiency of up to 98%. The inverter will always require a level of energy consumption to operate and losses will always be incurred whilst inverting. The good news is such losses are minimal.

More importantly, due to rigorous European benchmark standard test parameters, such level of efficiency is beyond impressive when compared to the competition. Test parameters which help to ensure the best performance for solar PV systems incorporating Fronius inverters.

Average Inverter 94%
Fronius Primo (avg) 97%

Above: Solar inverter European efficiency.


The base Fronius Primo inverter guarantee is a 5-year parts and labor warranty. Expandable warranty options are available for purchase through Fronius, however, cost and availability will vary depending on the country of which the installation occurs.

The most common warranty upgrade is the additional 5-year parts only warranty. Certain regions around the world such as Australia have enjoyed a complimentary offering of this upgrade (via redemption) for the last 2 to 3-years. 

Be warned, additional costs under these particular warranty upgrades will still see the consumer out of pocket for both shipping and labour in the event of a warranty claim.

Average Inverter (base)
Fronius Primo (base)
SolarEdge (base)

Above: Base manufacturer warranty on a scale of 12-years. (Longest central inverter base manufacturer warranty).

Tech Insight: Fronius Primo inverters like near all standard string inverters contain electrolytic capacitors. Often the first point of failure (if installed in a protected and well-ventilated area) for many string inverters. Generally speaking, the service life for electrolytic capacitors within solar inverters is often between 5 to 10 years.


Fronius Solar.web cloud-based remote monitoring software is a cut above most other manufacturer supplied monitoring options. Once commissioned and configured (a vital element which should be completed by the installer) an end user gains access to expanded features:

  • Basic live energy production.
  • In-Depth production analysis.
  • Historical data logging.
  • System savings in monetary value.
  • CO2 savings.
  • Programmable automatic reporting features.
  • Advanced email warning and notification system (including energy fluctuations, system dropouts, earth fault alarms).
    Assign alternative users and administrators.

The Fronius Solar.web solar monitoring portal is one of the most progressive available. It takes a good investment to develop great software and Fronius are providing insightful tools for installers and consumers alike. Apple and Android versions of Solar.web appear to be evolving although are severely lacking in exceptional features incorporated from the browser based login.

Mobile Applications are without a doubt the future of solar inverter interaction. Ignoring this key feature could leave one exceptionally underwhelmed with less insight and control than originally anticipated.

When compared to alternative (paid) third-party energy monitoring packages such as Solar Analytics, the Fronius Solar.web software could use some improvement on the user experience for the advanced analytical and beneficial data. A minor negative in a superior software package.


Expect to pay double that of some of the cheapest single-phase solar inverter technology available. The hassle-free reliability of the Fronius Primo will easily make up for that though in the short, medium and long-term.

As a gauge, Fronius Primo 5.0-1 solar inverters are available online from USD 1400, AUD 1900, EURO 1200 excluding taxes, shipping and installation.

Source – Google.


The Fronius Primo inverter is an exceptionally refined solar inverter solution. A design which hasn’t wavered much within the last decade. The question mark though is what will Fronius do next? Alternative manufacturers have begun to make the solar inverter the new brain of the modern energy smart home and an innovative improvement here would be admired by many. There is though one vital element where Fronius trumps nearly all competition, reliability. The Fronius Primo is not perfect but as close to perfection one would get for what is available today.


View the Fronius Primo score below. Got questions? Or have an alternative perspective? Have your say in the comments.


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