The market provides the opportunity. How much of it becomes real revenue depends on whether the storage system executes the commands on site – on time, precisely and without interruption. In this article we show, with numbers, where the revenue of an aggregated battery storage system disappears and what a local controller changes.
Executive summary (PDF)BST Control Box product page
The starting point: what a 1 MW / 2 MWh storage can earn
Modelling the Hungarian day-ahead (DAM) and aFRR market prices of August 2026, the potential revenue of a 1 MW / 2 MWh storage was 12,448 EUR/MW/month – assuming 96% availability. That is the theoretical ceiling the aggregator can bid for. Everything below depends on the site.
Same storage, same market – different result
Based on the experience of a project we examined, the real availability of a storage system is typically 80–90% – it varies by project. Revenue scales linearly with availability, so the same storage on the same market earns:
| Scenario | Availability | Revenue (EUR/MW/month) |
|---|---|---|
| Potential (model) | 96% | 12,448 |
| Estimated reality | 80–90% | 10,374–11,670 |
| With BST Control Box (target) | 95% | 12,319 |
The difference between the estimated reality and the 95% target is 650–1,950 EUR/MW per month – 7,800–23,350 EUR per MW per year, or 2.8–8.5 million HUF. Not because the market changed, but because the site executed better.
Where does the revenue go – and what does a local controller do about it?
The aggregator decides on the bids and sends the baseline signal. A local controller – in our case the BST Control Box – executes it on site, protects the system and documents what happened. The two complement each other. Six typical loss points:
| Where is revenue lost? | What happens? | What does the BST Control Box do? |
|---|---|---|
| Communication loss | The link to the aggregator drops; the storage stands still or produces wrongly. | Watchdog: after 3–4 missed periods it alarms and switches to local fallback mode. Own UPS and LTE router. |
| Slow or imprecise execution | aFRR activation requires second-level tracking; peak prices bring the most. | Executes the baseline locally and immediately towards the PCS; sends measured data back to the aggregator. |
| Exceeding the contractual limit | Exceeding the connection contract means penalties or disconnection. | Stepped protection: curtail above 110%, BESS breaker after 20 s above 110%, main breaker above 120%. |
| Settlement disputes | Hard to prove afterwards what the aggregator requested and what really happened. | Time-stamped log of every aggregator command and of the actual execution. |
| Battery degradation | Too deep discharge and exceeding BMS limits shorten the lifetime. | SoC protection chain: discharge block, emergency charge, commands clipped to BMS limits. |
| Troubleshooting, downtime | Every hour of standstill is lost capacity and activation revenue. | Remote monitoring (ComAp AirGate), event log and alarms at PV, BESS, grid and communication level. |
How much is this worth on your storage?
Raising availability from 80–90% to 95% is worth the following surplus, calculated from the same starting point (lower value from 90%, upper value from 80% starting availability):
| Storage | Surplus / month (EUR) | Surplus / year (EUR) | Surplus / year (HUF) | Payback of the Control Box |
|---|---|---|---|---|
| 1 MW / 2 MWh | 650–1,950 | 7,800–23,350 | 2.8–8.5 M | 7–24 months |
| 2 MW / 4 MWh | 1,300–3,900 | 15,550–46,700 | 5.7–17.0 M | 4–11 months |
| 4 MW / 8 MWh | 2,600–7,800 | 31,100–93,350 | 11.4–34.1 M | 2–5 months |
The BST Control Box is a ComAp InteliNeo-based outdoor energy management cabinet (IP54, −15…+50 °C) with UPS and LTE router; the logic is programmed for each site according to the grid connection contract. Price: 4,980,000 HUF + VAT, monitoring 29,990 HUF/month. Payback is calculated with one Control Box, after deducting the monthly monitoring fee; larger sites are sized individually.
Works with any aggregator – and without one
- Standard Modbus TCP connection to the aggregator; when you change aggregator, the local control stays.
- Manufacturer-independent: 9 inverter/PCS manufacturers and 8 ComAp units – Sinexcel, Kehua, EVE, Huawei, CATL, Delta among others.
- Also for hybrid sites: PV curtailment, peak-load management, diesel genset, black start.
- Without an aggregator: schedule- and time-based control for self-consumption sites.
The calculation is illustrative, not an investment offer. Starting point: potential revenue modelled from the Hungarian DAM and aFRR prices of August 2026 (at 96% availability), scaled linearly with availability; the 80–90% starting range is an estimate; 365 HUF/EUR. Actual revenue depends on the site, the connection contract, the aggregator agreement and market prices.
Let us calculate it for your storage system
Send us the basic data of your site (storage size, connection contract, aggregator) and we return a site-specific calculation; in a free 30-minute engineering consultation we also review the connection contract.