Battery energy storage (BESS): how it works, what it costs and where it earns money in Moldova and Romania

What a BESS is and what it consists of

A battery energy storage system (BESS) is more than a rack of batteries. At industrial or grid scale it usually includes:

• lithium iron phosphate (LFP) cells and modules, grouped in racks;
• the battery management system (BMS), which monitors the voltage, temperature and state of charge of every cell;
• the power conversion system (PCS) — the bidirectional inverter between the battery's direct current and the alternating-current grid;
• the energy management system (EMS), which decides when the battery charges and discharges;
• the medium-voltage transformer, air conditioning, gas detection and fire suppression, usually in a container.

LFP chemistry dominates stationary storage because it is more thermally stable, withstands more charge cycles and is cheaper than nickel-based chemistries (NMC). Its energy density is lower, but for a container standing on a concrete pad, weight and volume matter far less than safety and service life.

MW and MWh: power, energy and duration

The ratio of energy to power gives the duration of discharge at full power. A 70 MW / 140 MWh system — such as the one being prepared in the CET-Nord project in Bălți — can deliver 70 MW for two hours. Fast frequency control needs 30–60 minutes; shifting solar output from midday to the evening calls for 2–4 hours.

Three details change real-world calculations:

• Usable capacity is lower than nominal capacity: manufacturers limit the depth of discharge to extend cell life.
• Auxiliary consumption by air conditioning and electronics continues even when the battery is idle.
• Degradation depends on the number of cycles, on temperature and on the state of charge at which the battery rests. Large projects plan for adding capacity (augmentation) during operation.

Where a battery's value comes from

1. Shifting energy in time. The battery charges when energy is cheap — increasingly at midday, when every solar park is producing — and discharges in the evening, at the consumption peak. The gain is the price difference minus efficiency losses.
2. Balancing services. System operators (Transelectrica in Romania, Moldelectrica in Moldova) buy reserves that respond within seconds or minutes. A battery is the fastest provider of such services.
3. Less energy lost at solar parks. When the grid cannot take all the output or the price turns negative, the battery keeps the energy for later and makes better use of the existing connection.
4. Peak shaving for consumers. A plant that would exceed its approved power can cover short peaks from the battery instead of applying for more power and new connection works.
5. Backup for critical loads — refrigeration, continuous processes, servers — if the system is designed to operate separately from the grid as well.

The best projects combine several revenue streams. That is why sizing starts from the purpose, not from a “round number” of MWh.

The market in 2026: Romania and the Republic of Moldova

Romania

• According to Transelectrica data quoted by the trade press, about 1,094 MW / 2,310 MWh of batteries were installed at the end of August 2026, including 100 MW and 335 MWh added in August alone; according to ANRE data, projects at various stages exceed 9 GW.
• GEO No. 134/2024 removed the double taxation of storage and excluded storage operators from the definition of final consumer for green certificates; ANRE Order No. 56/2025 established that network tariffs no longer apply to energy that is stored and fed back into the grid. The installation's own consumption, including losses, is still charged.

Republic of Moldova

• Law No. 164/2025 on electricity, in force since 19 August 2025, replaced Law No. 107/2016 and introduces storage facilities; they are admitted into operation on the basis of a certificate of conformity issued by ANRE.
• On 30 April 2026 a 60 MWh system next to a 50 MW solar park, financed by maib, was inaugurated in Rădeni (Strășeni district) — the largest in the country at the time of its inauguration.
• On 11 June 2026, Moldelectrica activated balancing services from solar plants with batteries (50 MW and 40 MW) for the first time, with a maximum reduction of 25 MW.
• The auction launched by the Ministry of Energy in December 2025 for up to 170 MW of wind power made storage mandatory: at least 0.25 MWh for every MW installed.

What a storage system costs

Prices have fallen faster than the market expected. The BloombergNEF survey of December 2025 shows:

These are pack prices, not project prices. A turnkey system includes the converters, transformers, containers, air conditioning, fire protection, the EMS, the grid connection, design and installation. IRENA puts the average cost of grid-scale storage systems at $192/kWh in 2024, 93% less than in 2010.

The economic assessment is done on cash flows: revenue from energy shifting and services, minus efficiency losses, auxiliary consumption, maintenance and capacity fade over time, discounted at the cost of capital.

Safety: the standards that matter

The main risk of lithium-ion batteries is thermal runaway — a reaction in which a faulty cell heats up uncontrollably and can ignite its neighbour. LFP chemistry has better thermal stability, but design remains decisive:

• IEC 62619 — safety requirements for industrial lithium-ion cells and batteries;
• IEC 62933 — the series of standards for grid-connected energy storage systems, including safety requirements;
• UL 9540A — the test method for fire propagation between cells, modules and racks;
• NFPA 855 — installation rules: distances, ventilation, detection and gas exhaust.

On site, this means distances between containers, gas and smoke detection, deflagration vents, fire-brigade access and an emergency response plan agreed with the emergency services.

How we size a BESS

1. Purpose. Evening energy sales, balancing services, peak shaving or backup — each needs a different ratio between MW and MWh.
2. Data. The consumption or generation curve in 15-minute steps over at least one year, and power quality data at the connection point.
3. Connection and regulation. The power admitted in the connection permit, metering, the commercial status of stored energy.
4. Simulation. Hourly or 15-minute operation, with efficiency, auxiliary consumption, degradation and the EMS strategy.
5. Technology and layout. Containers or cabinets, distances, foundations, access roads, fire protection.

A concrete example from Moldova: we are preparing five storage projects of about 5 MWh each at existing eligible producers. The battery and a new PV array dedicated to charging use the same transformer substation as the existing park, through a single hybrid converter and a separate meter. The park keeps its fixed tariff, and the energy from the battery is sold on the market. Together with the ECOENERGETICA Association and ANRE, we are working to clarify the regulatory framework for this scheme.

Frequently asked questions

Sources and references

1. NREL / NLR — Annual Technology Baseline 2025: Utility-Scale Battery Storage
2. BloombergNEF — Lithium-ion battery pack prices fall to $108 per kilowatt-hour — December 2025
3. IRENA — Renewable Power Generation Costs in 2024 — 2025
4. AGERPRES — ANRE removes the double tariffs on electricity stored and fed back into the grid — 08.07.2025, in Romanian
5. CMS — Romania removes double taxation of stored electricity from the legal framework — GEO No. 134/2024
6. Romania Insider — Market incentives and rising installed RES-E capacity encourage more BESS investment in Romania — 03.09.2026, Transelectrica data via Economica.net
7. Romania Insider — Romania’s battery storage project pipeline exceeds 9 GW — 21.07.2026, ANRE data
8. maib — Pioneering 60 MWh energy storage project financed by maib
9. Logos Press — Moldova used batteries to balance its power grid for the first time — 12.06.2026, in Romanian
10. FAOLEX — Law No. LP164/2025 on electric energy (Republic of Moldova)
11. Ministry of Energy of the Republic of Moldova — auction for wind power plants with storage — December 2025