Battery energy storage systems (BESS) are rapidly moving from being a purely technological investment to becoming a strategic part of how companies manage energy. Yet two batteries with the same power and capacity can deliver very different results.
With recently appointed Manager at EVN Supply, Patrick Vasitsch, we spoke about what companies should consider before investing in BESS, the role of an Energy Management System (EMS), and why technology alone is not enough to unlock the full potential of BESS.
For a company considering a battery system for the first time, where should it begin?
Patrick Vasitsch: The process should begin with the company’s energy profile, rather than with a catalogue of battery models.
A proper assessment looks at how electricity is consumed and generated throughout the day, across different seasons and over the course of the year. For companies with on-site photovoltaic generation, it is particularly important to understand when surplus electricity occurs, when demand is highest and how the two profiles could be better aligned.
The analysis should also consider the commercial terms of the company’s electricity supply and offtake agreements, the capacity and limitations of its grid connection and any expected changes in production or consumption.
Only then should the technical parameters of the battery be determined: power, usable capacity, charging and discharging capability, round-trip efficiency, state-of-charge limits and warranty restrictions.
The right system is not necessarily the largest one. It is the one designed around the company’s actual energy needs and the role that the battery is expected to perform.
When discussing BESS, the focus is often placed on the battery itself – its capacity, power and technology. But how important is the way in which the battery is managed?
Patrick Vasitsch: It is fundamental. The hardware defines what the battery is capable of doing, but the management strategy determines what it actually delivers.
A technically advanced battery can still create limited value if it is charged and discharged according to a fixed or overly narrow operating logic. The same asset can produce a very different result when its operation is coordinated with the company’s consumption, on-site generation, contractual energy prices and market conditions.
A BESS should therefore not be viewed simply as equipment for storing electricity. When managed properly, it becomes an active energy resource that can provide flexibility and improve the company’s control over its overall energy position.
What is a modern EMS and what role does it play in the value that a customer receives from a BESS?
Patrick Vasitsch: A modern EMS is far more than an on-and-off control system. It monitors the battery’s state of charge, available capacity, charging and discharging power, alarms and other technical parameters. Through secure and agreed interfaces, it can also receive schedules, setpoints and operating commands.
However, it is important not to confuse the EMS with the complete optimisation service.
The EMS is the technological platform through which the battery is monitored and controlled. Optimisation is the decision-making layer behind that technology: it determines which action should be taken, when it should be taken and what information should guide that decision.
Even a technically sophisticated EMS can remain limited if it operates without access to the company’s broader energy data or without a clear connection to the relevant commercial and market conditions.
How does the EMS decide when the battery should be charged or discharged?
Patrick Vasitsch: The decision should never be based on a single signal. “Charge when the price is low and discharge when it is high” may sound simple, but real-world optimisation involves a much wider set of considerations.
It is very important to consider consumption and generation forecasts, expected market prices, the battery’s state of charge and available capacity, technical limitations, round-trip efficiency, warranty conditions and the commercial terms under which electricity is supplied and purchased.
A strategy focused on only one parameter may improve the result in one area while creating a cost or missed opportunity elsewhere. For example, discharging at the first attractive price may leave insufficient capacity for a more valuable period later in the day.
Effective optimisation therefore does not seek the best result in one isolated hour. It aims for the best overall outcome across the relevant settlement period, while respecting the battery’s technical and operational limits.
How important is it for the EMS to coordinate the battery with photovoltaic generation, consumption and the grid? What are the long-term risks of choosing a closed system tied to a single manufacturer or contractor?
Patrick Vasitsch: A battery does not operate independently from the rest of the company’s energy system. An EMS that sees only the battery sees only part of the picture.
When the system also has visibility of photovoltaic generation, consumption, grid imports and electricity exports, it can support more informed operating decisions. Surplus on-site generation can be stored instead of being exported immediately, while the stored energy can be used later when it has greater value for the company.
This is also why integration is so important. A closed system may perform its basic technical function perfectly well, but still limit access to data, communication with external systems or the possibility of working with another service provider in the future.
Before selecting an EMS, companies should ask who owns and controls the operational data, whether the data are available in real time, whether the system provides documented interfaces and whether it can exchange signals securely with other relevant platforms.
Openness does not mean compromising safety or cybersecurity. It means avoiding unnecessary technological dependence and preserving the flexibility to adapt the system as the company’s needs and the energy market evolve.
From the perspective of a customer with an electricity supply agreement, what additional value is created when the BESS and EMS can communicate with the systems of the supplier and optimiser?
Patrick Vasitsch: The battery’s operation directly affects the electricity that the company imports from the grid, the electricity it exports and the schedules submitted to the market. It therefore cannot be optimised effectively without understanding that broader commercial context.
When the BESS can communicate with the systems of the supplier and optimiser, its operation can be aligned with actual consumption and generation forecasts, supply and offtake prices, market schedules and portfolio requirements.
This is where EVN Supply brings additional value. We combine the technical capabilities of the battery with our experience in electricity supply, offtake, scheduling, market positioning and portfolio management. The battery is not managed through an isolated algorithm, but as part of the customer’s wider energy position.
The customer should also be able to understand the outcome. This is why transparent data, a clearly defined calculation methodology and regular settlement reporting are an important part of the service. Optimisation should not be a black box.
Imbalance costs are not always visible in the headline price of an optimisation offer. Why is it important for customers to understand how this risk is allocated?
Patrick Vasitsch: Because a commercially attractive offer can look very different if imbalance costs and operational risks are ultimately transferred back to the battery owner.
The agreement should clearly distinguish between costs arising from the regular operation and optimisation of the battery and costs caused by circumstances within the Owner’s responsibility.
Under EVN Supply’s model, deviation and imbalance costs arising from regular battery operation and optimisation are not transferred to the BESS Owner. They are managed by EVN Supply as part of its portfolio-management activities.
The Owner may bear only direct, reasonable and verifiable costs that arise from a clearly attributable cause, such as unreported battery unavailability, an unreported technical limitation, incorrect operational data, failure to execute a valid operational instruction or unauthorised intervention by a third party.
This distinction is important. The customer should not be exposed to an undefined or open-ended balancing charge simply because the service provider has chosen not to manage that risk. Responsibilities, exceptions and calculation methods should be transparent from the outset.
If a company is planning an investment in BESS and EMS today, what would be your most important advice for choosing a solution that will remain relevant over the next five to ten years?
Patrick Vasitsch: Companies should look beyond the initial investment cost, the battery brand and projections of future revenue. They should evaluate the complete operating model.
The first question is whether the battery has been designed around the company’s actual energy profile. The second is whether the EMS provides secure access to data and sufficient integration flexibility. The third is whether the commercial model clearly explains how value is calculated and how risks, costs and responsibilities are allocated.
A long-term BESS investment should not depend on a closed technological environment, a one-dimensional optimisation strategy or an arrangement in which important market risks become visible only after operation has begun.
A strong optimisation partner should be able to explain not only when the battery will charge and discharge, but also why a particular decision is being made, how the resulting value will be measured and who is responsible for each associated risk.
Ultimately, the best solution is not simply the one that stores electricity. It is the one that manages every stored megawatt-hour with a clear technical purpose, commercial logic and transparent allocation of responsibility.