Turning Backup Generators into Profit Centers

For large commercial consumers like shopping malls in Thailand, a significant portion of the electricity bill is not for energy used (kWh) but for peak demand (kW)—the highest 15-minute average power drawn in a billing period. This "demand charge" can constitute 30-50% of the total bill. This Economics & Value case study shows how "Siam Paradise Mall" (pseudonym) leveraged its existing backup generators for peak shaving, transforming a cost center into a revenue-saving asset.

The Challenge: Exorbitant Demand Charges

The mall's peak demand consistently occurred on weekend afternoons, driven by thousands of air conditioning units, lighting, and escalators at full load. Their utility tariff included a demand charge of ฿XXX per kW. Reducing this peak by even 500 kW would result in massive monthly savings.

The Solution: Automated Peak Shaving System

The mall already had four 1,500 kVA silent diesel generators for backup. The project involved:

1. Advanced Paralleling Switchgear Upgrade: The existing ATS was upgraded to a fully automated paralleling system with grid-synchronization capability.
2. Peak Demand Controller: A smart controller was installed to continuously monitor the mall's total power import from the grid (via a utility meter pulse).
3. Load Bank (Optional but Recommended): To ensure generators could be tested under real load without disrupting mall operations.

How the System Operates

1. The controller tracks the rolling 15-minute average demand in real-time.
2. When it predicts the demand will exceed a pre-set threshold (e.g., 95% of the target limit), it sends a start signal to one or two generators.
3. The generators start, synchronize to the grid, and automatically pick up a portion of the mall's electrical load.
4. This reduces the power drawn from the grid, "shaving" the peak and keeping the demand charge low.
5. Once the peak period passes, the generators automatically shut down and return to standby mode.

The Financial Results

Conclusion: By implementing an intelligent peak shaving strategy, the mall achieved a rapid ROI on the control system upgrade. The generators now serve a dual purpose: emergency backup and monthly cost reduction. This case powerfully demonstrates that with the right technology & operation, a generator set is not an insurance cost but a strategic financial asset.