If you have a Fronius GEN24 Plus inverter and want to add storage, you have three options certified by Fronius: the Fronius Reserve PRO (the brand’s own battery), the BYD Battery-Box Premium HVS and the BYD Battery-Box Premium HVM. All three are high-voltage batteries using LiFePO4 technology, but they have significant technical differences that determine which is the best option depending on the size of your installation, your budget and your plans for expansion.
At FVComponentes.com we are Fronius System Partner and Official Service Partner in Spain. This guide explains the actual technical differences, the most frequently asked questions from installers and users, and how to choose the right battery for your Fronius inverter.
Before continuing: This guide applies only to investors Fronius Primo GEN24 Plus y Fronius Symo GEN24 Plus. The model GEN24 SC (Self-Consumption) does not have a battery input — if you’re not sure which model you have, check the following section first.
This is the most common mistake and the one that generates the most enquiries. Fronius sells two versions of the GEN24 with very similar names but very different functions:
| Fronius Primo/Symo GEN24 Plus | Fronius Primo GEN24 SC | |
|---|---|---|
| Battery input | ✅ Yes — compatible with Reserva PRO and BYD HVS/HVM | ❌ No — no battery power |
| Hybrid role | ✅ Yes — ESS, battery-powered stand-alone mode | ❌ No |
| PV Point (solar emergency) | ✅ Yes | ✅ Yes |
| Main use | Self-consumption + storage | Self-consumption without storage |
| Investor price | Mayor | Menor |
If you have a GEN24 SC and wish to add a battery in the future, you will need to replace the inverter with a GEN24 Plus. There is no firmware or hardware update available to enable battery input on the GEN24 SC.
You can identify your model on the inverter nameplate or in the Fronius Solar.web app: the Plus model is always indicated by the suffix “Plus” in the full name.
Fronius has officially certified three battery systems for its GEN24 Plus inverters. These are the only options with technical support guaranteed by the manufacturer and full integration with the Fronius Solar.web monitoring system:
Fronius’s own battery, designed specifically to integrate with the GEN24 Plus inverters. It offers the highest level of integration within the ecosystem — direct communication without intermediate protocols, simpler configuration and fully integrated monitoring via Solar.web without the need for additional modules.
| Parameter | Fronius Reserve PRO |
|---|---|
| Technology | LiFePO4 (lithium ferrophosphate) |
| Tension | High voltage (GEN24 Plus compatible) |
| Capacity per module | 3,15 kWh |
| Available configurations | 3.15 / 6.3 / 9.47 / 12.6 kWh (1 to 4 modules) |
| Guarantee | 10 years / 10,000 cycles |
| Inverter compatibility | Fronius GEN24 Plus Exclusive |
| Integrated management | Yes — no external BCU required |
| Solar.web Integration | Native — highest level |
Key advantage: the guarantee of 10,000 cycles is significantly higher than the BYD’s 6,000 cycles. For a system that cycles once a day, that equates to a cycle life of 27 years compared with 16 years — although both come with a 10-year warranty.
Key limitation: It only works with Fronius GEN24 Plus inverters. If you switch to a different brand of inverter in the future, you will also need to replace the battery.
The BYD HVS is the most flexible high-voltage modular battery system on the market. With 2.56 kWh modules, it allows the battery bank to be configured exactly to the required size with the finest granularity of the three options, and can be expanded by adding modules in the future without changing the management electronics.
| Parameter | BYD Battery-Box Premium HVS |
|---|---|
| Technology | LiFePO4 |
| Tension | High voltage (192 – 614 V) |
| Capacity per module | 2.56 kWh |
| Minimum system requirements | 2 modules = 5,12 kWh |
| Maximum settings | 8 modules = 20,48 kWh |
| Expansion steps | +2.56 kWh per module |
| Guarantee | 10 years / 6,000 cycles |
| Inverter compatibility | Fronius GEN24 Plus + SolarEdge, Kostal and others |
| BCU required | Yes — BMU v2 (included in the kit) |
| Solar.web Integration | Officially certified |
Key advantage: It is the only option if you plan to change your inverter in the future without replacing the battery. The BYD HVS is compatible with multiple brands of high-voltage hybrid inverters, which gives it a higher residual value. Furthermore, the 2.56 kWh granularity allows for more precise capacity adjustment than the Reserva PRO.
Key limitation: It requires at least 2 modules (minimum 5.12 kWh). If you need less than 5 kWh, the only option is the Reserva PRO.
The BYD HVM is the variant with the highest capacity per module in the BYD range. With 2.76 kWh modules and a minimum configuration of 3 modules (8.28 kWh), it is designed for installations that require greater storage capacity from the outset. Its main advantage over the HVS is its physical design: it stores more kWh in a tower of lesser height.
| Parameter | BYD Battery-Box Premium HVM |
|---|---|
| Technology | LiFePO4 |
| Tension | High voltage (126–537 V) |
| Capacity per module | 2.76 kWh |
| Minimum system requirements | 3 modules = 8.28 kWh |
| Maximum settings | 8 modules = 22.08 kWh |
| Expansion steps | +2.76 kWh per module |
| Guarantee | 10 years / 6,000 cycles |
| Inverter compatibility | Fronius GEN24 Plus + others |
| BCU required | Yes — BMU v2 (included in the kit) |
Key advantage: For installations requiring 8 kWh or more from the outset, the HVM takes up less space than an equivalent HVS. The difference in voltage range compared with the HVS (126–537 V vs 192–614 V) is generally irrelevant for installations using the Fronius GEN24 Plus.
Key limitation: The minimum of 8.28 kWh (3 modules) cannot be adjusted. If you need less than 8 kWh, the HVS is a better choice.
| Fronius Reserve PRO | BYD HVS | BYD HVM | |
|---|---|---|---|
| Technology | LiFePO4 | LiFePO4 | LiFePO4 |
| Minimum model | 3,15 kWh | 5.12 kWh (2 modes) | 8.28 kWh (3 modes) |
| Maximum | 12.6 kWh (4 modes) | 20.48 kWh (8 modules) | 22.08 kWh (8 units) |
| Expansion stage | +3.15 kWh | +2.56 kWh | +2.76 kWh |
| Guaranteed cycles | 10.000 | 6.000 | 6.000 |
| Warranty (years) | 10 | 10 | 10 |
| Compatibility | Fronius GEN24 Plus only | Multi-brand | Multi-brand |
| External BCU | Not required | BMU v2 (included) | BMU v2 (included) |
| Solar.web Integration | Native — maximum | Certified | Certified |
| Best for | Small to medium-sized installations, maximum Fronius integration | Medium-sized facilities with scope for expansion | Large-scale installations right from the start |
The battery capacity required depends on your night-time consumption — the energy you use from sunset to sunrise. The usual aim is to cover between 4 and 8 hours of average consumption whilst off the grid.
A simple way to estimate this: look at your electricity bill and work out your daily consumption (kWh/month ÷ 30). Roughly 40-50% of daily consumption takes place at night in a typical Spanish home.
| Total daily consumption | Estimated night-time consumption | Recommended battery | Suggested option |
|---|---|---|---|
| 5–8 kWh/day | 2–4 kWh per night | 3–5 kWh | Reserva PRO 3.15 kWh or BYD HVS 5.12 kWh |
| 8–12 kWh/day | 4–6 kWh per night | 5–8 kWh | BYD HVS 5.12–7.68 kWh (2–3 modes) |
| 12–18 kWh/day | 6–9 kWh per night | 8–10 kWh | BYD HVM 8.28 kWh (3-mode) or BYD HVS 10.24 kWh (4-mode) |
| 18–25 kWh/day | 9–13 kWh per night | 10–15 kWh | BYD HVS 10–12.8 kWh or BYD HVM 11–13.8 kWh |
| >25 kWh/day | >13 kWh per night | 15–22 kWh | BYD HVS or HVM at maximum capacity |
Important note: The power rating of the Fronius inverter (5, 6, 8 or 10 kW) does not directly determine the required battery capacity. What determines the size is your home’s energy consumption. A 10 kW Fronius inverter in an energy-efficient home can work perfectly well with a 5 kWh battery; whereas a 5 kW inverter in a home with high energy consumption may require a 15 kWh battery.
There is no one-size-fits-all answer, but there are clear criteria:
Yes, all three options are expandable, but under different conditions:
In all cases, the expansion requires the services of a qualified installer to reconnect the electrical system and update the settings on the Fronius inverter.
No. The Fronius GEN24 Plus is designed for batteries of high voltage only. Low-voltage batteries (Pylontech, Pytes, Victron LiFePO4 48V) are not compatible with the GEN24 Plus. If you require a system with a low-voltage battery, you will need an inverter with a different design, such as the Victron MultiPlus-II 48V.
The BMU (Battery Management Unit) v2 is the central control unit for the BYD HVS/HVM towers. It handles communication between the battery modules and the Fronius inverter. It is compulsory and is included in the BYD HVS/HVM starter kit. Version v2 is compatible with the Fronius GEN24 Plus; the older version (v1) is not.
No. The Fronius Reserva PRO is exclusive to Fronius GEN24 Plus inverters. If you switch to an inverter from another brand in the future, the battery will not be compatible and you will need to replace it as well. The BYD HVS and HVM are compatible with multiple brands, making them a more portable investment.
Yes. The GEN24 Plus can be installed in a purely on-grid configuration without a battery, and a battery can be added later when the budget allows. It is not necessary to install the battery at the same time as the inverter. You simply need to ensure that the inverter is the Plus model (not the SC model) so that the battery connection is available in the future.
They are not the same. The main difference lies in the size of the module and the minimum configuration: the HVS starts at 5.12 kWh (2 modules of 2.56 kWh) and the HVM at 8.28 kWh (3 modules of 2.76 kWh). For medium-sized installations between 5 and 8 kWh, the HVS allows for better adjustment of the initial capacity. For large installations starting directly at 8+ kWh, the HVM has a more compact design for the same capacity.
No. The HVS and HVM modules are not interchangeable and cannot be combined in the same tower. Each type requires its own BMU v2. However, you can have two separate towers with different types if the inverter supports two battery inputs — this does not apply to the Fronius GEN24 Plus in its standard configuration.
It depends on the inverter’s charging power and the size of the battery. A 5 kW Fronius Primo GEN24 Plus charging at full DC power would take approximately 1 hour to charge a 5 kWh battery from empty. In practice, charging takes place gradually throughout the day using surplus solar power, rather than in a single session.
At FVComponentes.com, we are a Fronius System Partner and an Authorised Service Centre in Spain. If you’re unsure which battery is best suited to your specific Fronius installation, just let us know the inverter model, the power rating and your estimated consumption, and we’ll provide you with a direct technical recommendation.
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