When selecting an energy storage system, the first question is not how many kilowatt-hours the battery should provide, but what task it needs to perform. Using daytime generation at different hours, supporting specific loads, and managing power demand are different operating scenarios. Capacity assessment becomes meaningful only after this objective has been defined.
Distinguish between power and energy capacity
Power is expressed in kilowatts (kW), while energy capacity is expressed in kilowatt-hours (kWh). Power indicates how much load the system can supply at any one time; energy capacity helps determine how long it can continue to do so. For example, the theoretical energy requirement of a constant 10 kW load over two hours is 20 kWh. Because this simple calculation does not account for losses and operating limits, it is not sufficient for direct product selection.
Understand when consumption occurs
Total monthly consumption provides a starting point, but interval-metering data is more informative for system sizing. The business’s shifts, short-term demand peaks, weekend operating pattern, and, where applicable, solar generation profile are assessed together. A brief load increase and a load that remains high for several hours may not require the same storage duration.
It is therefore useful to review different periods that are representative of the business rather than a single day. Seasonal operation, planned production increases, and new equipment should be added to the data file. The metering point and time interval associated with each dataset should also be specified.
Nameplate capacity alone is not enough
A battery’s nominal and usable capacities may differ. State-of-charge limits, conversion losses, temperature conditions, and changes in battery performance over time are considered in the technical model. The battery, power conversion equipment, and control system are also assessed together. The presence of an existing solar energy system does not mean that every storage product will be directly compatible.
Preparing for the initial consultation
Describe the expected function in one sentence and list the loads you want the system to support. Include available consumption records, generation data where applicable, and the target operating duration. The technical team can then compare scenarios and explain the conditions under which the selected power and energy values would be sufficient.
Do not look only for a single capacity figure in the assessment. Ask for the data used, the operating strategy, and the assumptions that could change the results. This provides a clearer view of how the proposed storage solution relates to your business’s actual requirements.
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