500 kW Battery Energy Storage System: What to Measure Before You Buy

Power vs Capacity: The kW/kWh Relationship

Power (kW) is the rate of charge or discharge; capacity (kWh) is the total energy stored. A 500 kW system with 1 MWh can deliver full power for 2 hours (C-rate 0.5C). With 2 MWh, it runs 4 hours at 0.25C. The C-rate tells you how fast you cycle the battery; higher C-rates stress cells and shorten life.

For industrial sites, we typically design for 1–2 hours of autonomy. That means a 500 kW unit with 500–1000 kWh. If you need longer, you increase capacity, not power. A 500 kW, 2 MWh system is common for peak shaving and backup.

Voltage Class and Grid Connection

At 500 kW, the connection is almost always three-phase low voltage (0.4 kV) or medium voltage (6/10/35 kV) via a transformer. At 0.4 kV, the current is about 720 A per phase at full load—that's heavy for a single feeder. Often we step up to 10 kV to reduce losses and allow longer cable runs.

You must verify the grid connection point's fault level, short-circuit capacity, and protection settings. A 500 kW inverter can cause voltage rise or flicker if the grid is weak. We always check the transformer's impedance and tap changer before committing.

Footprint and Siting

This class comes in three form factors: outdoor cabinet (IP55, ~2.5×1.5×2.2 m per 250 kW), 20-ft container (for 500 kW / 1 MWh, ~6×2.4×2.6 m), or an indoor room (ventilated, fire-rated). Containers are easiest for greenhouses and mines because they are pre-assembled and weatherproof.

Clearances: you need 1 m around the container for airflow and maintenance. Weight is about 12–15 tonnes for a 20-ft unit; check the soil bearing capacity. For indoor installations, you'll need a ventilation rate of at least 10 air changes per hour and a fire suppression system.

CAPEX Range and What Moves It

For a 500 kW / 1 MWh system, a realistic CAPEX range is $300,000–$450,000 (or roughly 11–17 million UAH). That includes the battery, inverter, BMS, container, and installation. Prices vary with cell brand (CATL vs others), cooling method (liquid cooling adds ~5%), and the complexity of the grid connection.

What moves the price: if you need a new medium-voltage transformer (+$20–40k), long cable runs, or a custom EMS/SCADA integration. Also, the inverter's grid-support functions (e.g., reactive power control) add cost. Without a load profile, that figure is rough—we always refine after the survey.

Pre-Design Survey Checklist: What to Measure, Pull, and Verify

Before any proposal, we do a site visit. Here's the checklist:

• Load profile: 15-minute interval data for at least one year. This drives the capacity and control strategy.
• Electricity tariff: Demand charges, time-of-use rates, and any feed-in tariffs. We calculate payback in months, not years.
• Grid connection: Voltage, fault level, and the point of common coupling. Verify if you can export power or only charge from the grid.
• Space: Dimensions of the proposed area, access for a crane, and ground conditions.
• Environmental: Temperature range, humidity, and dust levels (important for mines).
• Documents: Single-line diagram, transformer nameplate, and electricity supply contract.

Only after we have those numbers do we talk about batteries. Without them, any quote is a guess.