Product review: Fronius Primo Inverter

Published: 27 October 2019

The Fronius Primo Inverter is an excellent grid-tied inverter, ideal for Australia, with a simple design, several size options and simple installation.

Today we will examine one of the most interesting models for residential purposes, the Fronius Primo inverter

Fronius is one of the greatest brands in the solar industry. It is an Austrian manufacturer of solar electronics that has been involved in the market since 1992 with a wide range of products which has allowed the brand to earn well-deserved respect among customers and installers worldwide. 

Fronius offers storage solutions, software solutions for energy management, MC4 connectors, AC combiners and the star product of the brand: Fronius inverters.

This Fronius Primo model comes in diverse sizes and with many characteristics, making it suitable for multiple applications depending on the size and features of your system.

The first things you must know about this model are that the power range varies between 3.0 to 8.2 kW and which installations are mounted according to the SnapINverter generation of Fronius. This will be discussed below. 

Primo performs only under grid-tied features and is a single-phase transformerless inverter that works with a communication system incorporating WLAN and energy management features. 

Now that you have an overview of the inverter, let’s take a closer look at some of the features of this product.

Primo Inverter Installation

First of all, we must select the appropriate place for the installation of the inverter. 

There are some requirements that must be fulfilled in order to have a valid warranty from the company. 

One of them is that Primo needs to be installed vertically (on a wall) or horizontally (on the floor) on a solid, flat surface, whether indoor or outdoor. It is recommended it  not be exposed to direct sunlight) and should be installed below 4000m in height.

Moreover, you must take into consideration that the inverter expels hot air on the top that can reach up to 70°C. The inverter takes cold air from both the left and right sides, therefore, in order for Primo to perform efficiently with proper air circulation, no nearby surface must interact with or cut off cold or hot air circulation. 

In other words, install the inverter on an isolated wall. If, due to space limitations you need to install the inverter in a sealed area, forced air ventilation must be used for proper heat dissipation.

Regarding temperature and humidity levels, the inverter is able to work between -40°C and 55°C and in up to 100% of relative humidity, so this need not be an area of concern.

Fronius Primo Inverter

Now, one of the greatest advantages of Fronius is the simple installation procedure through their SnapINverter methodology. The mounting is really easy as all the connections are done with a lightweight, anodized aluminum mounting bracket. 

The methodology simply consists of opening up the package and unscrewing the bolts on the underneath side of the inverter to loosen the mounting structure. Then install the mounting structure on the wall using screwdrivers and once fixed, just place the inverter! 

The complete installation is fast and simple:

The Fronius Primo Inverter also allows you to perform updates to the inverter through the use of USB flash drive ports that are integrated in the mounting structure

Some other considerations at the moment of installation are related to the PV system that is going to be connected. It must be considered for grid tied purposes only, with ungrounded solar modules. Neither positive or negative poles of the modules should be grounded, but the neutral cable of the AC system must be grounded, otherwise it won’t be possible to install the inverter.

Maximum Power Point Tracking (MPPT)

Primo inverter models offer the possibility of adapting to environments where two independent MPPT inputs might be necessary. 

For instance, if you have two strings with different orientations it would be better to connect each string to a MPPT input because this allows the system to work in the most optimum way to perform tracking of the maximum power point.

In the case of shading in the modules, the inverter will locate the best possible value for power output.

Fronius Primo Inverter MPP & LMPP

Grid Tied Feature

As with any grid-tied inverter, the Fronius Primo inverter transforms direct current to AC current which is fed into the home system or to the public grid. 

Primo continuously monitors the public grid. If for any reason there is an interruption in the supply of electricity from the grid, the inverter will stop working and interrupt the power supply from the grid. 

It is designed to monitor and synchronize to voltage and frequency values of the grid and avoid anti-islanding conditions. 

Under no conditions will the inverter be able to generate its own frequency.

Besides, the inverter performs automatically. When enough irradiance is available and the modules are able to start producing DC, the inverter will monitor the frequency and voltage from the grid to start feeding AC to the system. When not enough irradiance is available, the inverter will shut down automatically. 

Moreover, if for any reason the operating temperature exceeds the maximum designed temperature value, then the inverter will reduce the power output for self-protection.

Monitoring and Displays

The Fronius Primo inverter also allows you to see the energy performance of the system at all times. 

Among other things, the homeowner will always be able to monitor the instantaneous AC power produced. 

Moreover, the inverter also has display options known as LOG and GRAPH, where all the recorded data since the inverter was installed has been stored and can be accessed by the user. This allows you to see how the PV system performance changes over time and over the year (interesting to evaluate energy productions across seasons). 

Among other things, the user/installer will be able to see:

  • AC output power
  • AC reactive power
  • AC voltage
  • AC output current
  • Frequency
  • PV array voltage
  • PV array current
  • AC Energy Yield
  • Earnings (based on currency selected)
  • AC Max Output Power
  • CO2 Savings
  • Operating Hours

As you can see it is uncomplicated and complete display of the overall performance of the system in a single day and over time, which allows the user to easily understand the many advantages of the PV system. 

Particularly, earnings, AC energy yield, CO2 savings and operating hours would be the most interesting features for homeowners. 

It’s always nice to see a graph showing the contribution you have made to the grid, to the environment and to your wallet as well!

On a more technical aspect, the inverter allows you to establish the grid voltage and frequency limits of the grid, set the power factor value, set AC power limits, display the five most recent grid faults, display PV insulation resistance and set MPPT inputs start voltage (between 80-800 V). 

Moreover, Primo offers troubleshooting and diagnosis of any possible issue in the inverter’s operation: overcurrent (DC or AC), exceeding voltage or frequency limits, grid faults, high internal temperature, communication errors, hardware or software problems, reversed AC polarity, insulation breakdown on solar modules and arc detection failures.

Primo Inverter: Datasheets and Specs

As with many other brands, Fronius presents the same configurations mentioned above for a single inverter model (Primo), but at the same time offers several options of Primo models that perform the same functions. 

Among them, there are three big sections, the 3kW series, the 4-5 kW series and finally the highest power output inverters.

3kW Series

The simpler inverter, ideal for residential purposes. 

This device contains several specs that will give you an idea if the inverter is suitable for your installation or not. 

Let’s take a look what Fronius has to offer.

The first thing that we must take a look at is the power rating of the inverter which is defined by the name of the model or the nominal output power in W. 

The 3.0-1 model is a 3000W inverter, the 3.5-1 model is a 3500 W and the 3.6-1 model is a 3600W. This is a reference to the typical power value in AC that the inverter can handle.

The next thing we should look at is the voltage level. This can be found on the nominal grid voltage parameter. 

Particularly, for this inverter the parameter says: 1~NPE 220/230/240 V. 

In other words, the inverter is single-phase with neutral phase and earth output cables and is able to set a nominal voltage at 220/230/240 V. 

What you need to do now is check the grid voltage of your location. 

Particularly for Australia, typical voltages are either 230 or 240 V, so this inverter would be perfect for applications in Australia. 

Another critical parameter of selection is the frequency of the inverter, the selection of which depends on the frequency of the grid that is going to be connected, for Australia the grid is 50 Hz, so as we can see the inverter can perform adequately in the Australian household.

Afterwards, we can take a look at the other features of the Primo inverter. 

For instance, the MPP voltage range is a typically important parameter to take into account, as it establishes the maximum and minimum number of panels that can be connected in series to form a string. For this model the range is between 200-800 V. 

We can also take a look at the maximum short-circuit current of the solar modules which is referred to as the parameter, that comes in the datasheet of any solar module. This value is typically way below 18 A, so the inverter can easily handle the current of any module.

Moreover, other more technical parameters like total harmonic distortion, power factor and maximum output current must be taken into account to match the requirements of the installation.

Among other factors, efficiency values, cooling system, IP protection, weight, dimensions, temperature and humidity ranges are all provided in the datasheet

As you can also see, the inverter provides the DC disconnector which is the protection device that acts to disconnect the inverter from the grid when the system fails in order to avoid any islanding operation.

4-5 kW series

Within the next series of Fronius Primo inverters you can find the 4kW, 4.6kW and 5kW versions. 

The only modifications are related to maximum power output and MPP voltage range.

5-8.2 kW series

The ultimate Primo generation inverter is the 5.0-1 Aus., 6.0-1 and 8.2-1. 

These models have the same characteristics of the 3kW, except for MPP ranges and nominal output power (4600 W, 6000 W, 8200W). 

Particularly the 5.0-1 Aus model presents a unique characteristic, which is that the inverter nominal output power is 4600 W but it’s able to provide up to 5000 W as extra power during a specified amount of time.


We have examined all the properties and features that are integrated with the Fronius Primo inverter. 

This is an excellent grid tied model inverter, ideal for installations in all of Australia, integrated with a simple design, several size options, simple installation procedures, compatible with accessories like the Fronius combiner box and with a friendly user interface that allows the homeowner and installer to take a quick overview of the performance of the PV system over the course of a day, month, year or even since the system was installed.

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