Start with the load, not the battery
Two numbers are constantly confused: how much power the site draws, and how much energy it needs to keep drawing.
The power figure — kilowatts — decides the inverter or PCS. The energy figure — kilowatt-hours — decides the battery. A cabinet sized only on kW will run flat in the first hour of a backup event; a cabinet sized only on kWh will trip on an inrush load it cannot supply fast enough.
So the first thing to get is a load profile, not a wish list. Fifteen-minute interval data for a normal working day and for the site's peak day is enough to size almost any commercial system. If interval data does not exist, the electricity bill's maximum demand reading plus the main breaker rating is a workable substitute — it will simply size the system conservatively.
Five numbers decide the cabinet
Send us these and the sizing stops being a guess.
- Peak demand (kW) — from the bill or the meter, not the sum of nameplates. Summing nameplates typically overstates demand by 30–50%.
- Backup duration (hours) — what the site must keep running, and for how long. A factory that only needs to ride through outages and shut down cleanly needs far less than one that keeps production running.
- PV capacity (kWp) and its inverter — how much of the daily energy comes from the roof, and whether the storage will be charged from PV, grid, or both.
- Grid constraint — export limit, demand charge, or a connection that cannot be upgraded. This is often what makes the economics work, and it decides whether the system must be behind-the-meter only.
- Ambient temperature and location — a shaded plant room and an unshaded roof in a hot climate are two different products, not two prices for the same one.
Air-cooled or liquid-cooled
Same chemistry, different heat path — and different maintenance.
| Model | Rated power / energy | Battery voltage | Cooling | Enclosure | Warranty |
|---|---|---|---|---|---|
| GCB-E50 | 50 kW / 50 kWh | 512 V | Air | IP54 | 5 years |
| GCB-E112 | 50 kW / 112.53 kWh | 358.4 V | Air | IP54 | 5 years |
| GCB-E241 | 125 kW / 241.15 kWh | 768 V | Air | IP54 | 5 years |
| GCB-E261 | 261 kWh cabinet | — | Liquid | IP54 | 5 years |
Air cooling is the lower-cost route and, in temperate climates with a shaded plant room, it is the right one. Liquid cooling costs more up front and pays back in two situations: high ambient temperatures, where air cannot hold the cells in their comfortable band, and high cycling rates, where the pack generates more heat per hour than air can remove evenly.
The honest test is the summer afternoon, not the annual average. A cabinet that is fine eleven months a year and derates in July is a cabinet that fails the project.
Sizing a worked example
A method you can repeat, not a number you can copy.
Take a site with a 400 kW peak, an average working-day consumption of 2,400 kWh, and a requirement to keep critical loads running for two hours at 150 kW during an outage. The energy requirement is 150 kW × 2 h = 300 kWh before efficiency and depth-of-discharge allowances — which lands above a single 241 kWh cabinet and points to either a larger cabinet or two units in parallel.
The daily arbitrage or peak-shaving side is a separate calculation: it is limited by how much energy can be shifted inside the tariff window, not by how big the battery is. Do this second, and size on it only if it is the actual business case.
This is why we ask for the load profile rather than promising a kWh figure in a catalogue: the same 400 kW site can justify 50 kWh or 500 kWh depending on what it is for.
Integration and compliance
The cabinet is one part of a system that has to pass inspection.
Plan for the PCS or inverter, the transformer where the site needs one, the EMS or site controller, and the protection and metering around them. On the compliance side, our LFP cells and packs are supplied with IEC 62619 and UN38.3 test documentation; cabinets carry CE and RoHS marking, and manufacturing is certified to ISO 9001 and ISO 14001. Where a project needs additional grid-code or fire-safety documentation, tell us the standard and we will confirm what can be supplied before quotation rather than after.
Commissioning matters as much as the hardware: state of charge limits, charge and discharge rates, temperature thresholds and the EMS schedule all have to be set at handover. A correctly sized cabinet with default settings will still underperform.
C&I BESS sizing FAQ
How do I convert my electricity bill into a battery size?
Take the maximum demand in kW and the monthly consumption in kWh. Demand sets the PCS rating; the difference between consumption during expensive hours and cheap hours sets the energy that can be shifted. Both numbers are on the bill, and together they are enough for a first-pass size.
Should I size for backup, for peak shaving, or for both?
Size for whichever drives the business case, then check the other fits. Backup is sized by critical load × hours; peak shaving is sized by the shiftable energy inside the tariff window. Systems sized for both are common, but one of the two is always the design driver.
How many cabinets can run in parallel?
Parallel configuration depends on the model and the PCS. Tell us the target energy and power and we will confirm the combination and the wiring in the proposal rather than quoting a nominal limit.
What warranty applies to C&I cabinets?
Five years across the GCB range, with the terms confirmed in the quotation. Cycle-life and capacity-retention conditions are stated in the warranty document, not inferred from a brochure figure.
Can the cabinet be installed outdoors?
The enclosure is IP54, which suits sheltered outdoor locations. For direct sun, coastal salt spray or flooding risk, the installation design — canopy, plinth, drainage — matters more than the IP number, and we will say so before you order.
Size your C&I project with us.
Send the load profile, the backup requirement and the site location. You get a sizing, a model recommendation and the documentation list — before any quotation.
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