Fronius Gets Back Into Solar Batteries With Reserva

It’s been a while between drinks, but Austria’s Fronius is back in the home battery manufacturing game. Here’s a first look at the Reserva.

Fronius is best known for its inverters, but the company once offered a home energy storage system called the Fronius Solar Battery.

The base model was 4.5kWh, but could be expanded to as much as 12kWh capacity (9.6kWh usable), and offered a 4kW continuous power rating at the 12kWh configuration. It wasn’t cheap (“reassuringly expensive” as SQ’s Anthony would say), could only be installed indoors and used for three-phase homes. Given its limitations, it didn’t come as a great surprise when the company stopped offering it.

Fronius Reserva Unveiled

Officially launched last week, the Fronius Reserva is a DC-coupled high-voltage battery offering usable capacities of between 6.3 kWh and 15.8 kWh. The base unit is expanded by adding up to 5 stackable modules of 3.15kWh each. The cells in the modules are lithium iron phosphate (LFP/LiFeO4) chemistry. Up to four battery towers (aka “stacks”) can be connected in parallel to achieve a maximum storage capacity of 63 kWh.

Unlike the Fronius Solar Battery, the Reserva can also be used for a single-phase home and is compatible with Fronius hybrid inverters such as the Symo/Primo GEN24 Plus, but not the Symo Hybrid. The compatibility chart here indicates the Primo GEN24 Plus (single-phase) is only compatible with Reserva 6.3 and 9.5; whereas the Symo GEN24 Plus (three-phase) is through to the 15.8.

The company says the Reserva is backup power and black start capable. A Fronius Backup Controller and Backup Switch is needed to enable automatic backup power switching.

The Reserva has an IP65 ingress rating, which means it can be installed outside (in “protected areas”) as well as indoors . The system has an operating temperature range of -20 C to 55 C. Dimensions range from 860 x 780 x 176 mm – 1,610 x 780 x 176 mm depending on the number of modules in a tower; so it’s quite a slim battery. Weights range from 85 kg to 187 kg.

As for country of manufacture, that’s not specified on the datasheet, brochure or website landing page. Usually Fronius gear is made in Austria, but that doesn’t necessarily mean it’s the case with the Reserva.

Monitoring of the Reserva is via Fronius Solar.web where all Fronius device monitoring is displayed. The company says data is stored exclusively on European servers, which is meant to reassure those who are particularly concerned with data being stored …elsewhere.

A Longer Warranty

The company’s original battery only had a 5-year warranty, whereas with the Reserva it’s 10 years.

According to Fronius CSO Harald Scherleitner:

“Longevity is particularly important to us at Fronius. We therefore guarantee that the Fronius Reserva will still deliver at least 80 percent of its usable energy after ten years from the start of the warranty.”

I haven’t seen a warranty document yet to check out the finer details, but 80% at the end of year 10 is pretty good; with many manufacturers only warrantying 60% – 70%.

I’ve asked Fronius if/when the Reserva will be available in Australia and will update this post when there’s further information.

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Update March 3, 2025: Fronius have told me they are planning to launch the Reserva in Australia at the end of the year.
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Approximate pricing isn’t known – but keeping in with Fronius tradition, the Reserva battery will likely also be “reassuringly expensive”.

I like Fronius gear and have a Primo SnapInverter (being phased out) and a Wattpilot EV charger. They do what it says on the tin, and reliably. While I didn’t experience any “wow” when reading about the Reserva, based on the company’s track record over the last decade it’s not unreasonable to suggest it should be the same.

The Reserva isn’t the only battery compatible with Fronius’s hybrid inverters. For example, there’s also BYD’s Battery-Box Premium HVS/HVM; although the HVS series no longer appears to be available.