Choosing a Battery Energy Storage System: From 50 kW to 5 MW

You don't pick a BESS by power rating alone. The right capacity depends on your load profile, tariff structure, and how long you need backup. Here's the logic we apply when sizing systems for Ukrainian industrial sites.

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Key parameters

Capacity range

50 kW – 5 MW

Typical discharge duration

1–4 hours (customizable)

Cell chemistry

LiFePO4 (CATL, other Tier-1)

Payback period

4–8 years, depending on tariff

Start with the Load Profile, Not the Power Rating

First, you need a 24-hour load curve — ideally every 15 minutes for a full year. Without it, any capacity figure is a guess. For peak shaving, look at the top 100–200 hours of demand: that's where you'll cut peak demand charges. For backup, define the critical load and required autonomy.

Only after you know the energy (kWh) you need to shift or back up do you size the battery. Power (kW) is secondary — it sets the charge/discharge rate, but it's the energy that determines the number of cells.

Match Discharge Duration to Your Application

A 1 MW BESS can be 1 MWh (1-hour discharge) or 4 MWh (4-hour). For frequency regulation, 15–30 minutes is enough. For peak shaving on a typical Ukrainian tariff, 2–4 hours is common. For backup, you might need 8 hours or more.

Our standard industrial systems are designed for 1C to 0.5C continuous, but we can configure higher C-rates if your grid code demands it. Don't oversize the battery for a short-duration need — that wastes money.

Voltage and Grid Connection Are Decisive

At 50–200 kW, you're likely connecting at 0.4 kV. Above that, you may need 10 kV or 35 kV. This affects transformer costs and protection. For instance, a 1 MW system at 0.4 kV would require enormous cables — it's not practical.

We always run a grid impact study before recommending a size. If your site has a weak grid, the BESS can also provide reactive power support, but that requires a four-quadrant inverter and changes the design.

Calculate Payback with Real Tariffs and Demand Charges

Payback for a BESS in Ukraine ranges from 4 to 8 years, depending on your tariff and how aggressively you operate it. The biggest savings come from cutting demand charges — that's the UAH/kW component. You can also arbitrage energy prices if you're on the day-ahead market.

Don't ignore degradation: LiFePO4 cells retain 80% capacity after 4000–6000 cycles. We model the project with a 10-year horizon, accounting for capacity fade and replacement costs. A rough estimate: for every 100 kW of peak shaving, you might save 50,000–100,000 UAH per month, but that's site-specific.

Mistakes We See Most Often

One common mistake is buying on price per kW — you end up with too little energy. Another is ignoring the transformer: you might need a dedicated one, which adds cost. Also, some clients expect the BESS to work as an UPS, but transfer times differ.

Another frequent error is not considering thermal management. Liquid cooling is essential for hot summers; air-cooled systems derate. Finally, don't skip the EMS/SCADA — without it, you can't optimize dispatch. We've seen systems that underperform because the control logic was too simple.

All capacity classes

Frequently asked questions

What capacity do I need for peak shaving?

It depends on your load profile and tariff. Typically, you'd size the battery to cover the top 100–200 hours of demand, with a discharge duration of 2–4 hours. For example, a 500 kW peak shaving application might need a 1 MWh system. We can help you estimate with your actual data.

How long will a LiFePO4 BESS last?

Industrial LiFePO4 systems last 10–15 years, with 4000–6000 cycles to 80% capacity. At 1 cycle per day, that's roughly 10–15 years. But calendar aging also matters — we design for a 10-year operational life with proper thermal management.

Can I use a BESS for backup power?

Yes, but you need to size it for the critical load and autonomy. For example, a 100 kW load for 4 hours requires 400 kWh. The transfer time is typically under 100 ms with an automatic transfer switch. For longer outages, you might want to pair it with a generator.

What's the difference between 0.4 kV and 10 kV connection?

0.4 kV is low voltage, suitable for systems up to about 300 kW. Above that, you'll need medium voltage (10 kV or 35 kV) to keep currents manageable. This requires a transformer and switchgear, which adds cost. We always include that in the design.

How much does a 1 MW BESS cost in Ukraine?

Installed costs vary, but for a 1 MW / 2 MWh system with liquid cooling and EMS, you can expect roughly $500,000–700,000 USD equivalent, depending on the configuration and site conditions. We provide detailed quotes after a feasibility study.

Figures shown are indicative. Exact sizing follows a site survey and load-profile analysis.