1.2 MW extrusion plant, two-phase BESS, RM 670k saved annually.
A Peninsular Malaysia extrusion site on TNB Bukan Domestik ToU. A recorded 676 kW Maximum Demand, driven by a recurring 20:00–22:00 evening peak, set the bill. UniBess proposed a phased BESS: a 250 kW pilot to validate the load, then a 2.5 MW deployment for the headline saving. Site anonymised; figures from the actual sizing study.
Two peaks set the bill. Both capped to target.
The headline numbers
Site context
Sector:
Plastics extrusion (anonymised).
Connection:
400 V, 3 Phase + Neutral.
Tariff:
TNB Bukan Domestik Time-of-Use (B2).
Recorded MD:
676 kW (Dec 2025 to Feb 2026 reference period).
Operating pattern:
Continuous operations with a recurring evening peak surge between 20:00 and 22:00.
Reference month bill:
approx. RM 151,500 (Caj Semasa, single sample month).
What the load data revealed
UniBess collected 47 valid days of 15-minute interval data over a 12-week period. Four findings shaped the BESS sizing:
Morning surge.
Daily spikes above 1,300 kW between 08:30 and 10:00, outside the MD target window we focus on first.
22:00 load step.
At exactly 22:00 the load shot vertically past 1,000 kW, a start-up coinciding with the off-peak boundary.
Stable baseline.
During the critical 14:00 to 22:00 peak window, average load was remarkably consistent at approximately 485 kW.
Tail-end spikes.
Over 60% of billable MD spikes (500 to 676 kW) erupted in the final 90 minutes of peak hours (20:30 to 21:59).
Conclusion:
target the 676 kW evening hill first with a pilot, then expand to full peak coverage.
The two-phase design
250 kW / 522 kWh pilot
Right-sized pilot targeting the recurring 20:00 to 22:00 evening spike. 2 cabinets, 8 weeks of operational data, validates EMS dispatch logic.
- MD reduction target: approx. 73 kW.
- Estimated annual saving: approx. RM 85,000.
- Phase 1 de-risks Phase 2: if the pilot underperforms, no Phase 2 capex is triggered.
- Indicative CAPEX: approx. RM 1.25 M, or lease at approx. RM 18,500/mo.
2,500 kW / 5,220 kWh full
20 cabinets in AC-coupled cluster, 8-hour continuous dispatch across the full 14:00 to 22:00 peak window. Drops MD from 676 kW down to a 100 kW target.
- MD reduction target: approx. 576 kW continuous shaving (676 → 100 kW).
- Estimated annual saving: approx. RM 670,000.
- Plus approx. RM 30,000/year of energy arbitrage on the peak/off-peak delta (additional upside).
- Indicative CAPEX: approx. RM 11 M, or lease at approx. RM 142,000/mo.
Performance commitments in the contract
- ≥ 60 kW guaranteed monthly MD reduction (Phase 1, in the 20:00 to 22:00 setting interval).
- ≥ 500 kW guaranteed monthly MD reduction (Phase 2, across the full 14:00 to 22:00 peak window).
- ≥ 97% availability per measurement year, peak hours.
- 85% to 78% round-trip efficiency, Year 0 to Year 10.
- ≥ 70% capacity retention by Year 10 of nameplate.
- Measurement: rolling 12-month average against a Counterfactual MD baseline (12 months pre-commissioning, ±10% Reference Load Envelope).
Why phased, not single-shot
The temptation with a project like this is to skip the pilot and go straight to Phase 2. We argued against that for three reasons:
Load profile validation.
47 days of data is enough to size; it's not enough to trust the size. Phase 1 puts hardware on site running real dispatch, and we can re-run sizing against actual telemetry before we commit Phase 2 capex.
EMS tuning is site-specific.
Dispatch parameters get tuned for at least 4 to 6 weeks in real operations. Better to do that on a 250 kW system than a 2.5 MW one.
Capex de-risking for the client.
If Phase 1 underperforms the model, the client has spent RM 1.25 M, not RM 11 M. If it meets target, Phase 2 unlocks with strong confidence.
Phased delivery is how serious BESS gets built. Anyone offering a turnkey 5 MWh deployment on a never-seen-before load profile is selling you risk, not engineering.
Have a site that looks like this one?
Send us TNB invoices (any 3 months) and a brief site description. We'll respond within one business day with a first-cut sizing estimate and indicative payback for your specific situation.