Energy balancing: what it is, its types and how it works in grids, loads and batteries
The energy balancing process is the set of strategies and technologies used to keep a power system within stable operating conditions when generation, consumption, loads or internal elements are not perfectly balanced. The concept appears at several levels of the energy sector: from the real-time balance of an electricity grid to load distribution in an industrial facility or cell balancing within a battery.
Simply referring to “balancing” can therefore mean different things depending on the context. In a transmission grid, Grid Balancing means continually correcting the difference between generation and demand to maintain frequency. In a building or charging centre, Load Balancing distributes or shifts loads to avoid exceeding electrical limits. In a three-phase network, balancing aims to distribute power between phases. And in a BESS, the BMS can balance the cells to prevent one of them from prematurely limiting the whole battery.
The common principle is always the same: detect a difference, have the flexibility to correct it and act before the imbalance causes losses, overloads, frequency deviations or reduced capacity.
In systems with high renewable penetration, this function becomes more important because solar and wind generation are variable. The system needs resources capable of increasing or reducing power, shifting consumption, storing energy or exchanging it with other areas to maintain balance continuously.
Energy balancing: the same objective at different levels
There is no single type of balancing. The main difference lies in which variable is being balanced and at what scale. This classification helps explain why technologies as different as a battery, an electric vehicle charger or a hydropower plant can contribute to balancing functions.
| Type of balancing | What is balanced | Standard scale | Example |
|---|---|---|---|
| Grid Balancing | Generation and demand | Power system | BESS responding to an aFRR signal |
| Load Balancing | Load distribution or profile | Building, industrial facility or microgrid | Dynamic management of EV chargers |
| Phase Balancing | Power between phases | Three-phase network | Redistribution of single-phase loads |
| Battery Cell Balancing | State of charge between cells | Module or battery | Passive or active balancing by the BMS |
These levels are complemented by commercial or portfolio balancing. Producers, electricity retailers and other participants aim to bring the energy they actually generate or consume close to their scheduled market position. When a deviation occurs, the system must correct it physically and then settle it financially.
In Europe, the Electricity Balancing Regulation establishes the framework for procuring, activating and exchanging balancing services. ACER explains that transmission system operators use these services to correct mismatches between supply and demand and maintain system frequency. ACER.
Grid Balancing: keeping generation and demand in balance
The Grid Balancing process, also known as grid balancing, is probably the concept’s most important application from a power system perspective. At every instant, generated power and consumed power must remain sufficiently close. When an imbalance occurs, frequency begins to deviate from its nominal value.
In most of continental Europe, the reference is approximately 50 Hz. If generation is below demand, frequency tends to fall; if generation is excessive, it tends to rise. Transmission system operators use reserves and balancing energy to correct these deviations. ENTSO-E structures European balancing through different layers of response. The best-known include:
- FCR (Frequency Containment Reserve): a very fast response intended to contain the initial frequency deviation.
- aFRR (automatic Frequency Restoration Reserve): an automatically activated restoration reserve.
- mFRR (manual Frequency Restoration Reserve): a restoration reserve activated through manual or semi-automatic signals or processes.
- RR (Replacement Reserve): replacement resources used in certain systems and time horizons.
The ENTSO-E Electricity Balancing Guideline aims to enable countries to share balancing resources and allow new technologies, such as demand response and renewables, to participate in these markets. A BESS is particularly well suited to certain Grid Balancing functions because it can change its power rapidly. It can charge when generation is excessive and discharge when generation is insufficient. However, it is not the only technology available: hydropower plants, flexible generation, interconnections and controllable demand can also provide balancing.
The large-scale deployment of solar and wind does not remove this principle; it increases the need for forecasting and flexibility. The more variable generation becomes, the more important it is to have resources that can respond to forecast errors, ramps or production deviations.
Load Balancing and Phase Balancing: balancing demand within an installation
The Load Balancing process operates at a different scale. Rather than balancing the entire power system, it distributes or adjusts loads within an installation to prevent transformers, service connections, lines or contracted power limits from being exceeded.
A common example is electric vehicle charging. Suppose a building has 300 kW of available capacity and twenty 22 kW chargers are installed. Their total theoretical power would be 440 kW, above the limit. A Load Balancing system can dynamically reduce the power of some chargers to keep total consumption below the available 300 kW. In this context, it is useful to distinguish between:
- Static Load Balancing: assigns preconfigured fixed limits.
- Dynamic Load Balancing: measures installation consumption in real time and automatically redistributes the available power.
Dynamic balancing is common in EV chargers, smart buildings, data centres, industrial facilities and microgrids. It can be coordinated through an EMS to decide which loads to reduce, shift or supply from storage.
Phase Balancing: balancing the three phases
Three-phase networks can also experience imbalance between phases. If many single-phase loads are concentrated on one phase, the currents become unbalanced. This can increase losses, neutral current, heating and power quality problems.
The Phase Balancing process aims to distribute loads more evenly between L1, L2 and L3. This can be done during electrical design by redistributing circuits, or through electronics and smart systems capable of dynamically changing the phase used by certain loads. Although Load Balancing and Phase Balancing are related, they are not exactly the same: the former manages how much power each load uses; the latter also addresses how that power is distributed between phases.
Battery balancing: passive and active
Battery balancing operates at another, entirely different level. Here, the objective is not to balance the grid or a building’s loads, but to prevent battery cells from developing excessively different states of charge. In a Battery Rack, small differences in manufacturing, temperature, internal resistance and degradation can cause one cell to reach its upper or lower voltage limit before the others. That cell then limits the usable capacity of the whole battery.
Passive balancing
The passive balancing method partially discharges the more highly charged cells through resistors. The surplus energy is converted into heat. It is a simple, inexpensive and widely used architecture.
Active balancing
The active balancing method transfers energy from cells with a higher state of charge to those with a lower state of charge, or between a cell and the whole battery. It is more efficient and can operate at higher currents, but requires more complex and expensive electronics. “Active vs passive” is therefore a valid classification for cell balancing, but should not be used as a general classification for all energy balancing. Other areas use different terms: static/dynamic for load management or automatic/manual for certain grid reserves.
Which technologies make balancing possible?
Modern balancing increasingly depends on flexible resources capable of rapidly changing their consumption or production. There is no single dominant technology because each is better suited to a different scale and response speed.
The BESS can absorb or deliver power within seconds and participate in frequency services, arbitrage and congestion management. The demand response reduces or shifts loads when the system needs it. Hydropower plants and other flexible generation units can increase or decrease production. The interconnections enable energy exchange between areas facing different conditions.
In local installations, an EMS coordinates renewable generation, storage and loads. The SCADA system provides the measurements and signals needed to determine the asset’s state, while control algorithms decide how to respond. Distributed generation can also participate. A portfolio of batteries, electric vehicles, heat pumps and industrial loads can be aggregated to act as a single flexibility resource. Balancing thus moves beyond relying exclusively on large power plants and begins to incorporate distributed assets. The logic can be summarised as follows:
Measure the imbalance → have flexibility available → act → check the new balance
Why balancing is particularly important with renewable energy
Solar and wind depend on variable weather resources. Production can be forecast with considerable accuracy, but never perfectly. A cloud, a wind ramp or a deviation from the forecast can rapidly change the available power.
Balancing absorbs these differences without compromising system stability. This may involve charging a BESS, activating reserves, reducing demand, increasing flexible generation, exchanging energy with another area or, in specific situations, temporarily curtailing renewable production. A power system with high renewable penetration therefore needs more than additional installed MW: it also needs flexibility, storage, forecasting, control and balancing markets capable of coordinating all these resources.
The importance of balancing depends on the level being analysed. In a national grid, it protects frequency and security of supply; in a factory, it prevents overloads; in a three-phase network, it reduces imbalances; and within a battery, it improves cell utilisation. All share the same idea, but use different technologies and metrics.