1 MW Battery Energy Storage System: What to Check Before You Design

Power vs. Capacity: The kW/kWh Relationship and C-Rate

A 1 MW battery can deliver 1000 kW for a limited time. Capacity is in kWh. A 2 MWh unit at 1 MW gives 2 hours of discharge (C-rate 0.5C). A 4 MWh unit gives 4 hours (0.25C). The C-rate is simply the ratio of power to capacity: 1 MW / 2 MWh = 0.5C. Choose the C-rate based on your application—peak shaving might need 1-2 hours, frequency regulation needs 15-30 minutes, solar shifting needs 4+ hours.

Don't oversize capacity if you don't need it. That adds cost and footprint. But undersizing means the battery cycles deeper, which shortens life. For a 1 MW project, typical capacity is 2-4 MWh, but that is a starting point, not a rule. Without a load profile, that figure is rough.

Voltage Class and Connection Type for 1 MW

At 1 MW, you have two realistic options: connect at 0.4 kV (low voltage) or step up to 10(6)/35 kV via a transformer. At 0.4 kV, cable cross-sections get large and losses rise. For distances over 100 m, 10 kV is usually better. Most industrial sites have a 10/0.4 kV transformer; you can connect the BESS on the LV side, but check the transformer's spare capacity.

If you are doing grid services like frequency regulation, you likely need a dedicated transformer and a medium-voltage connection. The grid operator's requirements dictate this. At 0.4 kV this will not work if the site has a weak connection or if the BESS is far from the main switchboard.

Footprint and Siting for This Class

A 1 MW / 2 MWh system can fit in a 20-ft container (about 15 m²). For 4 MWh, you might need two 20-ft containers or one 40-ft (about 30 m²). Outdoor cabinets (IP55) are possible for smaller capacities, but 1 MW often requires a container due to thermal management and safety distances.

Indoor rooms are also possible, but you need fire suppression, ventilation, and access for maintenance. Containers are simpler to permit and can be placed on a concrete pad. Allow 1.5 m clearance for maintenance. Check local fire codes—some jurisdictions require separation from buildings.

Noise is a consideration: liquid cooling is quieter than air cooling, but still expect fan noise at night. Siting near a substation reduces cabling costs.

Grid Constraints and Interconnection Review

Before anything else, pull the site's utility bill and one-line diagram. You need to know the maximum import/export limit, the transformer rating, and the fault level. The grid operator will require a connection study if you plan to export power. For ancillary services, you must verify that the site can respond to dispatch signals within 1 second—this affects the control system design.

Check for voltage fluctuations: a 1 MW step can cause a noticeable voltage rise at the point of connection, especially on a weak grid. You may need a static var compensator or a transformer with on-load tap changer. Frequency regulation requires a ramp rate of 100% in 1-2 seconds, which is feasible with LiFePO4.

CAPEX Range and What Moves It

For a 1 MW / 2-4 MWh system, CAPEX typically ranges from $300,000 to $600,000 depending on capacity, container vs. cabinet, and grid connection work. That is an honest range without an exact price because too many variables are site-specific. What moves it: battery price (LiFePO4 from Tier-1 like CATL), inverter type (PCS), transformer, installation labor, and the distance to the grid connection point.

Add costs for civil works, fire suppression, and grid studies. A 1 MW system with 4 MWh of capacity will cost more per MWh than a 2 MWh system because the inverter and grid connection are the same. Expect payback of 5-8 years for peak shaving if the tariff spread is at least 5 UAH/kWh. Without that tariff spread, the payback stretches beyond 10 years—don't believe anyone who promises 3 years.