Fronius Reserva vs Reserva PRO: the key differences and which one to choose

Fronius currently offers two ranges of high-voltage batteries for self-consumption: Reservation y PRO Booking. They share the same philosophy — lithium iron phosphate, DC coupling, modularity and a ten-year guarantee — but they are not the same battery, nor are they designed for the same purpose.

The difference isn’t that one is «the good one» and the other «the cheap one». They cover different capacity ranges and have different compatibility limitations. Let’s take it step by step, with the official technical specifications to hand.

The short answer

• Primo GEN24 Plus inverter (single-phase)? Standard capacity, and only 6.3 or 9.5. The Primo does not support larger capacities.
• Three-phase residential installation of up to 16 kWh? Standard tariff. It works out cheaper per kWh.
• Do you need more than 16 kWh? PRO version. The standard version has a capacity of 15.75 kWh; the PRO version has a capacity of 31.9 kWh in a single tower.
• Are you running low on toilet paper in the staff toilet? Standard clearance: 176 mm compared with 449 mm.

What really sets them apart: the module

The PRO module holds 26 % more whilst weighing about the same. This allows the PRO to reach much higher without increasing the number of parts.

Available configurations

Fronius Reserva — 2 to 5 modules

Fronius Reserva PRO — 3 to 8 modules

A detail that is often overlooked: the PRO Reserve There is no two-module version. The minimum setting is three, which equates to 11.9 kWh. If you need less than that, your best option is the Standard Reserve.

Both families accept up to 4 batteries in parallel, so the actual height is well above that of a single tower.

Compatibility with inverters

Both ranges work with Fronius Primo GEN24 Plus, Symo GEN24 Plus and Verto Plus, including the SC versions. However, there is one limitation that affects the entire project:

The Primo GEN24 Plus inverters (single-phase) only support Reserva 6.3 and Reserva 9.5. They are not compatible with the 12.6 or the 15.8, regardless of their power rating. If you need more than 9.45 kWh, you’ll need a three-phase inverter. And as the PRO starts at 11.9 kWh, The PRO range is beyond the capabilities of any single-phase Primo model.

Remember also Fronius’s general rule: the suffix Plus This is the one that indicates the battery input. A GEN24 without ‘Plus’ is mains-powered only and does not support storage.

Full technical comparison

Storage: the figure nobody looks at until the battery runs out

The two towers cover very different areas:

• Booking: 772 mm wide × 176 mm deep. Flat tower, designed to be placed against a wall.
• PRO Booking: 579 mm wide × 449 mm deep. Narrower at the front, but two and a half times deeper.

In a narrow utility room, the Standard Reserve fits where the PRO does not. If the problem is the wall width, the PRO takes up 193 mm less space at the front. Both also require 300 mm clear space on either side and a durable, non-flammable surface.

Cost per kWh: the PRO is not any cheaper

Two honest interpretations of this table.

In both ranges, the larger the unit, the cheaper the cost per kWh. The BMS and the base unit are a one-off purchase, and their cost is spread across more modules. Increasing the number from 6.3 to 15.8 reduces the cost per kWh by 19 %.

And for the same capacity, the Standard Reserve is more economical. A Reserva 15.8 (15.75 kWh) costs €5,604; a Reserva Pro 16.0 (15.92 kWh) costs €6,768. They are An extra €1,164 for just 0.17 kWh more.

If your installation falls within the Standard range and your inverter supports it, the Standard model is the sensible choice. The PRO model is justified when you need capacity that the Standard model cannot provide, or when you prefer fewer modules for the same amount of energy.

Which one to choose, depending on your situation

Choose Fronius Reserva if:

• Your inverter is a single-phase Primo GEN24 Plus — there’s no alternative here
• You’ll need between 6 and 16 kWh
• The available clearance is limited (176 mm compared with 449 mm)
• Do you want the best price per kWh?
• You are going to install it in a location where high temperatures are reached (up to 55 °C as opposed to 50 °C)

Choose the Fronius Reserva PRO if:

• You need more than 16 kWh: the standard version isn’t enough
• Are you looking for 24, 28 or 32 kWh in a single tower?
• Would you prefer fewer modules for the same capacity?
• You should take into account the warranty specified in 80 % health status ten years ago

Frequently asked questions

Can I upgrade a Standard Reservation with PRO modules?

No. They are different modules in terms of capacity, voltage, format and connection technology. Each range is expanded with its own modules.

What is the smallest Fronius battery available?

The Reserva 6.3, with two modules and 6.30 kWh. The PRO starts with three modules (11.9 kWh).

What is the maximum capacity I can install?

A PRO tower reaches 31.9 kWh with eight modules, and both ranges support up to four batteries in parallel. For projects like this, please contact us for sizing advice.

Do both of them work during a power cut?

Yes, provided that the installation includes the backup fitting. With the Fronius Backup Switch Either the Backup Controller or the system switches to Full Backup mode automatically or manually, without the need for an additional switch box.

Can they be installed outdoors?

Both are suitable for indoor and sheltered outdoor use, with an IP65 rating. «Sheltered» means protected from direct rain and sunlight: a garage or an enclosed porch are suitable, but an exposed wall is not.

What sort of guarantee do they offer?

Ten years each. The PRO’s terms and conditions also specify a health status of 80 % at the end of the period.

Are they suitable for a Fronius Symo Hybrid?

No. The documentation expressly excludes the Symo Hybrid.

In summary

The Standard Reserva is the obvious choice for residential self-consumption: the best price per kWh, lower installation costs, and the only model compatible with Primo single-phase inverters. The Reserva PRO is designed for situations where the Standard model falls short: more than 16 kWh and up to 32 kWh in a single tower.

At FVComponents we are Fronius System Partner and Official Service Partner in Spain. If you’re not sure which range is suitable for your inverter or how much capacity you need, please get in touch with us before you buy and we’ll sort it out with you.