Introduction
Deciding to build an energy storage system is just the beginning. Equally important is the question: how to build it and who will be responsible for what?
The Polish BESS (Battery Energy Storage System) market is maturing at an express pace. In December 2025, NFOŚiGW (National Fund for Environmental Protection and Water Management) published a list of 183 energy storage projects qualified for co-financing with PLN 4.15 billion from the Modernisation Fund. Interest in the program was enormous – applications were submitted for projects with a total value exceeding PLN 70 billion, almost seven times more than the available budget.
For many investors, this is the moment when key decisions about contract structure must be made. The choice of delivery model affects risk, costs, and subsequent operation for the next 15-20 years.
In this article, I will discuss three key decisions you need to make:
- Construction model: EPC Full Wrap vs Owner-Supplied Equipment + BoP
- Maintenance model: LTSA vs Full O&M
- Equipment selection approach: Lowest CAPEX or TCO optimization?
Part 1: EPC Full Wrap vs Owner-Supplied Equipment + BoP
What’s the difference between these models?
EPC (Engineering, Procurement, Construction) Full Wrap is a model where a single contractor delivers everything: the BESS system (batteries, inverters, BMS), BoP (Balance of Plant) – MV/HV infrastructure, transformers, switchgear, civil works, grid connection, and commissioning. You sign one contract, you have one responsible partner.
Owner-Supplied Equipment + BoP is a model where the investor independently purchases the BESS system directly from the manufacturer (CATL, BYD, Sungrow, Solax, and others), while a separate contractor handles installation and Balance of Plant.
Why does the Owner-Supply model seem attractive?
At first glance, Owner-Supply offers tangible benefits:
- Direct relationship with manufacturer – you negotiate directly with the supplier, without intermediaries
- Lower equipment price – savings of approximately 10-15% on equipment by bypassing EPC margins
- Full control over technology – you choose exactly the system you want
- Avoiding possible delays – you are in direct contact with the supplier so you will know sooner when there might be a delay
Sounds good? The problem is that these savings, without proper support within the investor’s organization, often prove illusory.
Hidden costs and risks of the Owner-Supply model
Integration risk
BESS is not a plug-and-play product. The system must work together with:
- PCS (Power Conversion System)
- MV (Medium Voltage) transformers and switchgear
- SCADA (Supervisory Control and Data Acquisition) and EMS (Energy Management System)
- Grid protection systems
- Fire suppression systems
- Cooling infrastructure (HVAC)
When something doesn’t work, the blame game begins:
Battery supplier: “Our system works flawlessly. The problem lies with the integration.”
BoP contractor: “We installed everything according to specification. The equipment doesn’t meet parameters.”
Result: The investor sits in the middle with a non-functioning asset and two parties pointing fingers at each other.
Hidden costs
Those “savings” of 10-15% quickly melt away when you add:
| Item | Additional cost |
| Technical Owner’s Engineer (integration supervision) | +5-8% |
| Extended timeline (coordinating two parties) | +3-6 months |
| Additional integration testing | +2-3% |
| Warranty non-compliance risk | Difficult to quantify |
| Legal costs (two contracts instead of one) | +1-2% |
In practice, a “savings” of 15% can turn into an additional cost of 5-10%.
Warranty coordination
This is one of the most underestimated problems. Imagine the situation:
- Battery warranty: 15 years from the manufacturer
- BoP warranty: 2 years from the contractor
- Integration warranty: …who provides it?
When in year 5 the system starts losing performance, determining the cause (battery degradation? cooling problem? EMS error?) becomes a nightmare.
Why does BESS EPC Full Wrap make sense in Poland?
Single point of responsibility
Performance guarantee with “teeth” – the contractor is responsible for the entire system. When something doesn’t work, you know who to call. There’s no blame-shifting game.
Polish market specifics
- Grid Code compliance requires integrated testing of the entire system
- Fire safety certification (CNBOP requirements – Scientific and Research Centre for Fire Protection) needs a coordinated approach
- Acceptance by PSE (Polish Transmission System Operator) or DSO (Distribution System Operator) assumes an integrated system, not a collection of components
Risk transfer
In the EPC Full Wrap model, the contractor takes on:
- Integration risk
- Schedule risk
- Performance risk
- Regulatory compliance responsibility
You pay more for equipment, but you buy peace of mind.
When can Owner-Supply make sense?
There are situations where Owner-Supply is justified:
- You have your own experienced technical team
- You’re delivering a series of identical projects and building competencies
- You have a strategic relationship with a battery manufacturer
- You accept higher risk in exchange for potential savings
For most investors delivering their first or second BESS project in Poland, EPC Full Wrap is the safer choice.
Part 2: LTSA vs Full O&M – who maintains your storage system?
After building an energy storage system, another question arises: who will maintain it for the next 15-20 years?
What is LTSA?
LTSA (Long-Term Service Agreement) is a service agreement with the BESS system supplier. It typically covers:
- Battery containers, cells, modules, BMS (Battery Management System)
- Cooling systems inside containers
- Container inverters / PCS (if supplied by the BESS manufacturer)
- Software updates
- Replacement of defective components
What does LTSA NOT cover?
This is where problems begin. A standard LTSA typically does not cover:
- MV/HV infrastructure (switchgear, transformers)
- Facility-level SCADA integration
- 24/7 monitoring
- On-site action coordination
- Safe Work Method Statements preparation
- Fire suppression systems outside containers
- Grid protection systems
- Civil works and site maintenance
- EMS/optimizer coordination
- Communication with DSO/TSO
- Investor reporting
The coverage gap problem
Imagine: Your LTSA guarantees 95% availability of battery containers. The containers work perfectly. But:
- MV transformer failure → entire facility offline
- SCADA communication problem → optimizer cannot execute scheduled dispatch
- Power outage → facility shut down, who will restart it?
Your storage system isn’t earning, but the BESS supplier reports: “container availability: 98%”. Technically true. Practically – a disaster.
What does Full O&M offer?
Full O&M (Operation & Maintenance) is a comprehensive agreement for maintaining the entire facility with a single provider:
| Scope | LTSA | Full O&M |
| Battery containers | ✅ | ✅ |
| MV/HV infrastructure | ❌ | ✅ |
| Facility-level SCADA/EMS | ❌ | ✅ |
| Fire suppression systems | Partial | ✅ |
| Site and fencing | ❌ | ✅ |
| DSO coordination | ❌ | ✅ |
| Facility availability guarantee | ❌ | ✅ |
| 24/7 monitoring | ❌ | ✅ |
Key difference: facility-level vs component-level
- BESS LTSA provides guarantees at the component level
- Full O&M provides guarantees at the facility level
For a bank financing the project, a facility availability guarantee is far more valuable than a container availability guarantee.
Costs: LTSA vs Full O&M
Full O&M is more expensive – typically 30-50% more than LTSA alone. But:
- You eliminate costs of coordinating multiple suppliers
- You have one invoice instead of several
- You avoid coverage “gaps”
- You simplify reporting for banks
- You can expect guaranteed availability at the system level
- You have a partner monitoring your facility 24/7
The 15-year question
Before making a decision, ask yourself:
Do I prefer a guarantee that my containers work, or a guarantee that my storage system earns?
If the latter – Full O&M is probably the better choice.
Part 3: Cheapest equipment or lowest TCO?
The CAPEX optimization trap
Many investors conduct detailed bid analyses, comparing every line item. CAPEX (Capital Expenditure) is analyzed down to the last penny. And OPEX (Operating Expenditure)? “We’ll deal with that later.”
This is a serious mistake.
BESS is not a one-time purchase
Your BESS must operate for 15-20 years. A system that’s offline doesn’t generate revenue – it generates losses.
Sources of downtime:
- Planned maintenance and servicing
- Waiting for spare parts
- Failures requiring service intervention
- Coordination problems between suppliers
Availability mathematics
Let’s assume:
- Storage system: 10 MW / 20 MWh
- Arbitrage revenue: PLN 350-500/MWh
- Maximum 2 cycles per day (40 MWh/day)
- Annual throughput: ~14,600 MWh
Annual revenue at 95% availability: PLN 4.8 – 6.9 million
Each percentage point of availability is worth PLN 50-73 thousand annually.
A supplier who saved you PLN 500,000 on CAPEX but delivers a system with 92% instead of 95% availability (3 percentage points difference) costs you PLN 150-220 thousand annually. Over 15 years, that’s PLN 2.3 – 3.3 million in lost revenue.
Of course, this is a simplified model – a real analysis should account for battery degradation over time (typically 2-3% annually), seasonality of price spreads on the day-ahead market, limitations from manufacturer warranties (e.g., maximum annual cycles), and other revenue streams (capacity market, ancillary services) – but it serves to illustrate the point.
What to look for when choosing a supplier?
Service presence in Poland
- Does the supplier have technicians in Poland?
- What is the guaranteed response time?
- Is the spare parts warehouse in Poland or “in Europe” (meaning 2,000 km away)?
Real availability guarantees
- How is availability calculated? (facility-level or component-level?)
- What’s excluded from the calculation? (time waiting for parts? planned maintenance?)
- What are the penalties for not meeting guarantees?
Long-term supplier stability
- Will this company exist in 10 years?
- Is it a manufacturer or just a reseller?
- What’s their strategy for the Polish market?
Case study: False savings
An investor received two offers:
- Offer A: PLN 45 million CAPEX, 95% availability guarantee, local service
- Offer B: PLN 41 million CAPEX, 92% availability guarantee, service from abroad
Offer B was chosen – a “savings” of PLN 4 million.
In the first year, actual availability was 88% (spare parts problems). Revenue loss: ~PLN 1.2 million.
After 5 years, the PLN 4 million “savings” turned into a PLN 2 million loss.
Summary: Key takeaways
Delivery model
- EPC Full Wrap is the safer choice for most investors in Poland
- Owner-Supply makes sense only with significant experience and a series of projects
- Apparent savings of 10-15% often disappear after adding hidden costs
Maintenance model
- LTSA covers only part of the facility – make sure you understand the gaps
- Full O&M costs more but provides guarantees at the facility level
- For banks, facility-level guarantees are far more valuable
Equipment selection
- Don’t optimize only CAPEX – what matters is TCO (Total Cost of Ownership) over 15-20 years
- Each percentage point of availability is real money
- Service presence in Poland is not “nice to have” – it’s a necessity
Need support?
Choosing a BESS project delivery model is a decision that will affect your investment for the next two decades. If you’re planning to build an energy storage system and want to discuss your options – contact GreenEdge Solutions.
We help investors with:
- Analyzing delivery models and their impact on project risk
- Component selection
- Preparing technical specifications and RFPs (Requests for Proposal)
- Evaluating contractor bids
- Contract negotiations
📧 contact@greenedge-solutions.com
🌐 www.greenedge-solutions.com
Related articles:
BESS Project Development in Poland: Why Most Energy Storage Projects Never Get Built
How to Choose an EPC Contractor for Your Battery Storage Project in Poland