Fronius solar inverters: the UK range, specs and warranty

Fronius is an Austrian inverter maker with a long track record in UK home solar. Its domestic ranges are the Primo GEN24, a single-phase hybrid inverter family running from 3.0 to 8.0 kW with a 10.0 Plus version also sold here, and the Symo, a three-phase family from 3.0 to 8.2 kW in the current GEN24 generation. The company was producing 70,000 inverters per month as of 2024¹.

For a UK household the headline terms are these: registering the inverter on Fronius Solar.web secures 10 years of free warranty cover for inverters below 50 kW, and a paid extension can take that to 15 years, but only if bought within the first 6 months of the warranty starting². Every GEN24 and GEN24 Plus inverter comes with a PV Point backup socket as standard, which can supply up to 3 kW to a single-phase socket during a grid outage, but only while the sun is shining³. UK distributor prices for the Symo range start from £1,078.34 excluding installation⁴.

The maker behind the inverters

Fronius describes the inverter as "the heart and brains behind your PV system"⁶, and the company's scale is unusual among inverter makers, with a production capacity of 70,000 inverters per month recorded for 2024¹. Fronius states that it produces its inverters "in compliance with strict quality guidelines in Europe"⁷, which shortens the supply chain for a UK buyer relative to ranges built further afield, though the company remains a foreign manufacturer and warranty support runs through its own organisation.

The inverter's role in the household's independence is double-edged, as it is for every string inverter. It converts the panels' direct current into mains alternating current and monitors the entire photovoltaic system⁸, so the home's solar generation depends on this one box working. It also creates dependencies of its own: on the grid for the export and import it manages, on Fronius for firmware and warranty, and on the company's Solar.web platform for monitoring and warranty registration. The GEN24's battery capability can be activated later with a software upgrade, which we cover under backup power.

Symo versus Primo: matching the range to your property

The split between the two families is the supply type. The Primo is single-phase, the configuration of a standard UK domestic supply; the Symo is three-phase, the configuration of larger homes, homes with three-phase supplies and small commercial buildings. Fronius's own overview lists the Primo at 3 to 6 kW single-phase and the Symo at 3 to 10 kW three-phase⁹, while the individual model pages and datasheets run the Primo GEN24 from 3.0 to 8.0 kW and the Symo from 3.0 to 8.2 kW¹⁰. The ranges differ because the overview groups power classes and the model pages list the appliances actually sold; the model pages are the ones to check against a quote.

Both families are transformerless in design¹², which is now normal for string inverters and reduces weight and standing losses relative to the older transformer designs. The Symo Hybrid datasheet lists a DC input voltage range of 150 to 1000 V¹³, which gives installers latitude on string length. The older non-hybrid Primo, described in a 2017 datasheet as "the ideal inverter for private households"¹⁴, has been superseded by the GEN24 generation for new installations. A fuller explanation of the three-phase range is on our Fronius Symo inverters page, and the general background is in solar inverters explained.

Primo GEN24: single-phase units between 3 and 10 kW

The Primo GEN24 is the range most UK homes will be quoted, because it matches a single-phase 230 V supply⁹. Fronius publishes model pages for the 3.0, 3.6, 6.0 and 8.0 kW versions¹⁵, and a 10.0 Plus single-phase hybrid version is sold in the UK as part of a hybrid storage package¹⁸. Each model in the range is fitted with a DC disconnector and can be installed indoors or outdoors¹⁶.

The Plus designation matters when a battery is planned. The GEN24 can be activated to support battery operation at any time using the Fronius UP.storage software upgrade, which converts a GEN24 into the GEN24 Plus hybrid inverter³, so a household can install the inverter first and add storage later without replacing the box. That upgrade path is a genuine independence gain, though it depends on Fronius continuing to supply and support the software. The wider choices are set out in hybrid inverters and adding battery storage to a solar system.

Symo: three-phase inverters from 3.0 to 8.2 kW

The Symo is the three-phase family, with power categories ranging from 3.0 to 8.2 kW across the current model pages⁵. Fronius publishes pages for the 3.0-3-M, the 6.0-3-M and the 8.2-3-M¹², all transformerless and three-phase. A UK distributor lists the wider Symo range at 3.0 to 20.0 kW⁴, which reflects the commercial end of the family; the domestic three-phase models sit at the smaller end of that span.

Three-phase suits homes with a three-phase supply, larger arrays, or loads such as heat pumps, car chargers and workshop equipment that benefit from balanced phases. The Symo 8.2-3-M also provides dynamic feed-in control with self-consumption taken into account¹¹, which matters where an export limit applies under G100; our export limitation page explains that regime. The distributor listing notes that the older Symo inverters are gradually being replaced by the Symo GEN24 up to 10 kW and the Verto up to 33.3 kW⁴, so a quote naming a plain Symo rather than a Symo GEN24 is worth querying. The mechanics are covered in string inverters for home solar.

What the specifications reveal about efficiency, cooling and construction

Fronius does not publish a single headline efficiency figure for the GEN24 range in the material here; what it does publish, prominently, is the cooling design. Active Cooling Technology is integrated as standard in all Fronius inverters¹⁹, and Fronius claims three consequences: the inverters deliver higher yields, have "a longer service life than inverters with passive cooling", and are "basically maintenance-free"¹⁹. Active cooling keeps the power electronics of the inverter at a low temperature⁷, and the intelligent active airflow also makes it possible to mount the inverters side by side¹⁹, which helps in tight plant rooms.

These are maker claims, and they are claims about the maker's own products, so they carry that weight rather than an independent test result. The design logic is straightforward: electronics kept cooler degrade more slowly, and a fan-cooled inverter can be sited in places a passively cooled one cannot. The GEN24 model pages confirm active cooling across the range¹⁶. What the specs do not tell a household is how the inverter will be configured: string design, shading and export settings shape real yield more than the cooling badge. Those factors are covered in reading a solar panel datasheet and how shade affects output.

Running appliances from surplus solar: backup capability on the GEN24

The GEN24 and GEN24 Plus inverters come as standard with PV Point, a basic backup power feature²⁰. In a grid outage, the PV Point can supply a single-phase socket with up to 3 kW of power, as long as the sun is shining³. The model datasheets repeat the condition: the inverter "supplies backup power to connected devices via a protected socket (as long as the sun is shining)"¹⁷. That is a real but narrow form of independence: a fridge, a phone charger or a router can keep running through a daytime cut, but nothing runs at night, and nothing runs without panels producing.

Full backup, meaning the whole house and operation after dark, needs the GEN24 Plus hybrid inverter with a battery, drawing on the PV module array and the battery²¹. Fronius describes the GEN24 Plus as a versatile hybrid inverter allowing battery storage and customised backup power solutions to be integrated²⁰, and parallel energy flows are possible, so the household can charge a battery while supplying loads²².

Surplus control is the other half. Fronius inverters have four integrated digital inputs and outputs and can be connected to third-party components such as a heat pump, pool pump or air conditioning system²³, and Fronius frames its systems around e-mobility, heat generation or battery storage⁶. The Fronius Ohmpilot sends surplus solar to hot water²³, an approach our solar diverters page covers in depth. What a GEN24 cannot do is free a home from the grid: it is a grid-tied inverter, and its backup functions are limited by design.

Solar.web: tracking output, export figures and how to sign up

A Fronius inverter with integrated data communication monitors the entire photovoltaic system and transmits the status live on Solar.web⁸, Fronius's free monitoring tool²⁴. Registration is free at www.solarweb.com using the inverter serial number²⁵, and the same registration is what unlocks the free warranty extension, so monitoring and warranty are one process rather than two.

For the household, Solar.web gives live generation status and keeps the PV system up to date²⁵. For installers it adds fleet monitoring in real time, remote fault monitoring and add-on simulations for battery storage or the Ohmpilot²⁶. The dependence to note is that live monitoring runs through Fronius's own platform and an internet connection; the inverter keeps working without it, but visibility and remote fault detection do not. Our monitoring a solar PV system page sets out the general picture.

Cover of 10 years as standard, extendable to 15, plus registration requirements

The warranty terms are set out in Fronius's warranty document. For inverters from 0 to 49 kW in country group 1, the warranty period is "10 years in total (= 5 years FRONIUS WARRANTY PLUS and 5 years FRONIUS WARRANTY thereafter)"²⁷. The warranty period starts with the date of initial commissioning of the covered product²⁷. The UK warranty page states the practical rule plainly: register to secure 10 years of free and reliable warranty cover for inverters under 50 kW².

Registration has a deadline and a method. The inverters must be "properly registered at https://www.solarweb.com/ within thirty (30) months of the initial delivery by FRONIUS ex works"²⁷, and new Fronius inverters commissioned on or after 1 June 2026 must be registered in Fronius Solar.web to qualify for the free warranty extension²⁸. Registration needs the serial number, the installation date, the installation country and the installer²⁹, and the serial number is on the rating plate of the product²⁹.

Two further terms are worth knowing. A Fronius Datamanager fitted inside an inverter imports the warranty period of that inverter²⁷. And the warranty document applies to covered products purchased on or after 1 June 2026, with Fronius reserving the right to change conditions for later contracts²⁷, so the terms on any quote should be read as at its date.

UK pricing and stockists, and the shift towards later models

There is no fixed UK installed price for a Fronius inverter; what exists is a set of distributor prices for the hardware, and installer quotes for the fitted system. A UK distributor lists Fronius Symo inverters from £1,078.34 and Fronius Eco inverters from £2,493.40⁴. Hybrid storage packages list the Primo GEN24 6.0 Plus at £2,088.31 excluding tax, the 8.0 Plus at £2,446.93 excluding tax and the 10.0 Plus at £2,775.54 excluding tax¹⁸. At the commercial end, the Verto 27.0 kW is listed at £3,297.04 and the Verto Plus 15.0 kW hybrid at £3,993.08³⁰. For context, independent UK guidance puts replacing a solar inverter at about £500 to £1,000³², which shows how the Fronius hardware sits above the generic replacement figure; the VAT position is not stated in the distributor listings, so read them as listed prices rather than confirmed VAT-inclusive ones.

Availability is shifting. The distributor notes that the older Symo inverters are gradually being replaced by the Symo GEN24 up to 10 kW and the Verto up to 33.3 kW⁴, and the Verto Plus range extends the hybrid line to three-phase homes³¹. For a household weighing independence, a Fronius inverter converts panel output into usable power and can manage a battery and surplus heating, but it keeps the home tied to the grid, to Fronius for firmware, warranty and the UP.storage upgrade, and to the Solar.web platform for monitoring and registration. The full context on system costs is in how much do solar panels cost in the UK, and the wider picture is in our solar PV guide.