Factory Battery Storage Sizing: A Practical BESS Guide

YINTU ENERGY STORAGE GUIDES

Start with the load profile. Define power, delivered energy and the operating strategy before selecting equipment.

A factory battery should be sized around a measurable operating task: limiting grid demand, shifting solar generation, or supporting defined loads during an outage. The total electricity bill alone cannot tell you the required battery size. Start with the load profile, decide what must change at the grid connection, and then specify power and energy separately.

YINTU is an energy storage solution provider. We help EPC contractors, installers and commercial customers turn site requirements into equipment configurations, working with manufacturing partners and the local project team.

1. Define the operating objective before choosing a cabinet

Objective	What determines power?	What determines energy?
Peak shaving	The required reduction in grid import during the billing interval	The area of the load profile above the target, plus operating allowances
Solar self-consumption	Surplus PV charging power and the later discharge requirement	Solar surplus available to store and demand available to absorb it
Time-of-use shifting	The planned charge/discharge rate and connection limits	The amount shifted between the available charging and discharge windows
Backup	Simultaneous critical loads, starting demand and inverter capability	Critical-load energy over the required outage period

Agree which objective takes priority. A reserve kept for backup may be unavailable for normal tariff-based dispatch. Model these functions together rather than assigning the full battery capacity to each one independently.

2. Collect the site data that changes the answer

Obtain interval meter data, preferably covering a full year and matching the utility billing interval. Record time zone, seasonal shutdowns and planned production changes.
Collect the complete electricity tariff, including energy charges, demand charges, billing windows and export conditions.
Record grid voltage, frequency, transformer rating, import/export limits and the electrical single-line diagram.
For solar integration, collect PV generation data, inverter models, export settings and planned array changes.
For backup, identify critical circuits, motor starting requirements, acceptable interruption time and required runtime.
Record available space, access, ambient temperatures, altitude, noise constraints and maintenance arrangements.

Monthly bills are useful for an initial screen, but they usually do not show how long each peak lasts. Do not infer a two-hour peak from a monthly maximum-demand number. The utility measurement interval also differs from a motor-starting transient, which needs a separate power-quality and inverter check.

3. Separate kW from kWh: a worked peak-shaving example

Assume a simplified factory load remains at 500 kW for two hours, while the project target is to limit grid import to 400 kW. Ignore solar during this interval so the calculation is easy to follow.

Required discharge power: 500 − 400 = 100 kW
Energy delivered to the load: 100 × 2 = 200 kWh AC

For a varying profile, add the required discharge power multiplied by each interval duration. An interval that is already below the target does not contribute discharge energy. Check whether the battery can recharge before the next peak without creating a new billed peak.

Next, distinguish delivered AC energy from nominal battery energy. For an illustrative design with 90% of the available battery energy allocated to dispatch and 95% discharge-path efficiency, the beginning-of-life requirement is 200 ÷ (0.90 × 0.95), or approximately 234 kWh. These percentages are calculation assumptions, not YINTU product ratings.

If the same duty must be met when retained capacity reaches an assumed 80% of its initial value, the screening result becomes 200 ÷ (0.90 × 0.95 × 0.80), or approximately 292 kWh. Add any auxiliary energy not already included in the efficiency boundary. Define reserve and usable state-of-charge consistently so they are not deducted twice. Charging losses and recharge time must be checked separately.

4. Convert the calculation into an equipment specification

A feasible energy calculation is only the first step. Confirm continuous AC power at the site temperature and altitude, battery current limits across the operating voltage range, permissible cycling, the selected PCS or hybrid inverter, and the grid connection. For a backup application, specify transfer equipment, islanding controls, protection and load steps; a grid-connected battery does not automatically provide UPS performance.

The 100 kW / 215.04 kWh commercial storage cabinet illustrates why both ratings matter. Dividing 215.04 kWh by 100 kW gives about 2.15 hours of nominal energy-to-power duration, before usable SOC, losses, auxiliaries and ageing. That number alone does not establish two hours of guaranteed AC backup. Review the wider commercial and industrial storage range after the required service has been defined.

5. Test the dispatch across the operating year

Compare the electricity bill with and without storage using the same load and tariff. Include charging demand, seasonal PV output, reserve settings, outages, auxiliary consumption and degradation. Stress-test repeated peaks, a low-solar day, reduced available capacity and a production expansion. Use the results to compare candidate sizes instead of selecting the largest cabinet that fits the space.

PNNL research on behind-the-meter sizing links the economic battery size to the load, tariff and battery characteristics. SAM documentation also distinguishes peak shaving, price-responsive operation and self-consumption. These are useful analytical frameworks; neither replaces the project electrical design.

6. Apply the lesson to industrial projects

The 4.2 MW / 9.03 MWh Hunan cement plant case provides a useful reference for coordinated industrial dispatch and export control. Its reported 110 kV connection makes the metering and control boundary especially relevant. A different factory requires its own study; the case size is not a sizing rule.

Frequently asked questions

Can I size storage from my solar array capacity?

Not on its own. You also need the time-matched site load, solar surplus, charging limits and discharge opportunities. A large PV array with little surplus can require a different storage configuration from an equally large array at a weekend-closed factory.

Should I add battery capacity for future expansion?

Document the expected change in demand and the date it is likely to occur. Compare staged expansion with installing all capacity now, including compatibility, space, controls and warranty conditions for later additions.

What should I send YINTU for a first review?

Send the country, voltage/frequency, interval load data, tariff, PV details, operating objective, critical loads and site conditions. Note which information is measured and which is estimated.

Turn your load data into a project configuration

YINTU coordinates equipment selection, manufacturer documentation, configuration review and agreed delivery and technical support. The selected manufacturer, certificates, warranty and service boundaries are identified in the proposal. Local qualified partners handle permitting, installation, grid approval and on-site responsibilities under the agreed scope. Send your factory requirements to YINTU for a sizing and configuration review.

Technical references

PNNL — Economic Analysis and Optimal Sizing for Behind-the-Meter Battery Storage
SAM — Behind-the-Meter Battery Dispatch and State-of-Charge Limits

Prepared by YINTU Energy · 22 October 2026. General project-planning guidance; final equipment ratings and design are confirmed for the selected model and site.