Big Yellow Self Storage, Fronius and EvoEnergy have collaborated on the commissioning of a new 63.8 kWh DC-coupled battery storage system, bringing Fronius’s newly launched Reserva Pro technology into a live commercial solar environment in the UK.
At first glance, the installation is easy to overlook. The battery system appears to be little more than a discreet grey enclosure, but behind that understated exterior is advanced DC-coupled storage technology, integrated and commissioned by EvoEnergy to help Big Yellow retain and use more of the renewable electricity generated onsite.
Together, the three companies are demonstrating how commercial solar assets can be taken a step further: moving beyond generation alone to more intelligent storage, management and use of onsite renewable energy.
Moving from solar generation to solar optimisation
Big Yellow’s significant investment in rooftop solar has already enabled more electricity to be generated directly at its stores.
The next opportunity is to improve how that electricity is used.
By capturing available solar generation and storing it for later use, Big Yellow can increase self-consumption and extract more value from the renewable infrastructure already installed across its estate.
This is becoming an increasingly important consideration for commercial solar asset owners.
As energy independence becomes an increasingly popular choice, the focus is moving beyond the question of how much renewable electricity can be generated towards how effectively that electricity can be retained, controlled and consumed onsite.
Fronius Reserva Pro
At the centre of the installation is Fronius’s new Reserva Pro battery platform which features cells and modules manufactured in Europe.
Introduced in 2026, Reserva Pro has been developed for commercial applications and larger energy users, using lithium iron phosphate battery technology within a modular high-voltage architecture.
A standout feature of the high-voltage battery is its flexible scalability with capacities of 12 to 32 kWh per tower and up to 128 kWh in parallel connection. The Big Yellow installation provides 63.8 kWh of usable storage capacity.
The installation of Reserva Pro batteries gives Big Yellow the benefit of Solar load shifting which means not just being able to move electricity use away from expensive or high-demand hours and into times when their solar panels are actively generating power but also charging the batteries when grid electricity is cheaper such as at night.
Reserva Pro is designed to operate as part of an integrated Fronius energy system, working alongside Fronius’s innovative hybrid inverter technology to manage solar generation and battery storage together.
A key feature of the project is its DC-coupled architecture.
Why DC coupling matters?
In a conventional AC-coupled battery configuration, solar electricity is first converted from DC into AC by the solar inverter.
If that electricity is subsequently stored, another conversion may be required before the energy enters the battery.
When that energy is later discharged, it must be converted back into AC for use within the building.
A DC-coupled system creates a more direct route between solar generation and battery storage ensuring fewer conversion losses. This is particularly relevant for businesses looking to maximise the value of onsite renewable generation.
EvoEnergy’s role: integrating the system
The project required the battery, inverter, existing solar PV installation, site electrical infrastructure and communications to function together as a single coordinated system.
EvoEnergy’s technology integration services are designed specifically around this type of requirement: ensuring technologies such as battery storage and solar inverter systems complement existing renewable assets to increase self-consumption, improve performance and create additional long-term value.
A shared view of the next stage of commercial solar
The project demonstrates a wider change taking place across the commercial renewable energy market.
Solar PV remains a highly effective way for businesses to generate renewable electricity onsite, but the value of those systems increasingly depends on how intelligently generation is managed.
For asset owners such as Big Yellow, storage provides an opportunity to increase the proportion of renewable energy used within the business.
For technology manufacturers such as Fronius, new DC-coupled battery platforms provide a way to integrate generation and storage more closely.
For renewable energy specialists such as EvoEnergy, the challenge is to bring those technologies together within the electrical and operational constraints of real commercial sites.
The collaboration between Big Yellow, Fronius and EvoEnergy brings all three elements together.
It is a relatively discreet installation, but one that reflects a much larger development in commercial renewable energy: the transition from simply generating renewable electricity to actively optimising when and how that electricity is used.