Understanding the Difference Between Prime and Standby Power Ratings
In today’s era of artificial intelligence, cloud computing, and massive data processing, the demand for highly reliable power supply in data centers has reached an unprecedented level. Among all backup power solutions, diesel generator sets play a critical role as the backbone of data center electrical infrastructure. This article explains the strategic importance of diesel generators in data centers and clarifies the often-confused concepts of prime power and standby power, helping you make informed purchasing decisions.
1. Why Data Centers Cannot Live Without Diesel Generators
For a data center, a short power outage of even a few seconds can lead to:
- Service interruptions
- Data corruption or loss
- Hardware damage
- Huge financial loss and reputational damage
This is why power protection design is considered the lifeline of a data center.
A complete data center power system typically consists of three layers:
- Grid Power – primary and cheapest source
- UPS (Uninterruptible Power Supply) – provides instantaneous, gap-free switching
- Diesel Generator Sets – provide long-term stable backup power
While UPS and diesel generators are both backup sources, their roles are completely different yet highly complementary.
2. UPS + Diesel Generator: Dual Protection System
UPS: Immediate Short-Term Protection
- Switching time: milliseconds
- Ensures zero downtime when grid power fails
- Battery capacity supports only minutes to a few hours
Diesel Generator: Long-Term Stable Power Support
Once the UPS battery begins to run low, the diesel generator automatically starts and takes over the load, delivering continuous and reliable power for as long as necessary—hours, days, or even weeks.
This creates a perfect synergy:
- UPS ensures instant protection; diesel generators ensure long-term stability.
One protects milliseconds, the other protects the future.
Both systems are indispensable to data center operations.
3. Cost Structure: Why Diesel Generators Are a Major Investment
In a typical data center, the cost distribution is:
- IT Hardware: 60%
- Infrastructure (power, cooling, electrical): 30%
- Civil Construction: 10%
Within infrastructure, the power system is one of the largest cost components.
Diesel generator sets account for:
≈ 23% of electrical infrastructure
≈ 6–7% of total data center construction cost
This highlights the irreplaceable value of diesel generators in safeguarding mission-critical facilities.
4. Technical Breakdown: How a Diesel Generator Set Works
A standard diesel generator set consists of six major components:
- Diesel engine
- Alternator
- Control system
- Radiator
- Fuel system
- Base frame
Operation Principle:
- Cleaned air enters the cylinder
- Diesel is high-pressure injected and mixed
- Piston compresses mixture → temperature rises to ignition point
- Fuel ignites → combustion expands → piston moves
- Crankshaft rotates
- Alternator rotor spins → electromagnetic induction generates electricity
Cost distribution inside a generator set:
- Diesel engine: ~65%
- Alternator: ~15%
- Controller, radiator, frame, wiring: remaining 20%
This is why choosing a good engine brand and quality alternator is critical.
5. Understanding Power Ratings: Prime Power vs Standby Power
Many buyers misunderstand generator ratings. International standards define four key power classifications:
(1) Prime Power (PRP – 主用功率)
- Continuous power available under variable load
- Allows 10% overload for 1 hour every 12 hours
- Commonly used for locations without grid supply
Example:
A 300 kW PRP generator can output 330 kW for 1 hour within a 12-hour cycle.
(2) Standby Power (ESP – 备用功率)
- Used only during emergency power outages
- No overload allowed
- If you run a 300 kW standby generator continuously at 300 kW, it is already in an overloaded state → shortens lifetime
(3) Limited-Time Power (LTP)
For fixed load and limited operational hours per year.
(4) Continuous Power (COP)
For continuous operation at constant load without overload capability.
How to Choose the Right Rating?
If your generator is used daily → choose Prime Power
If your generator is used only during power outages → choose Standby Power
If you mistakenly use a standby generator as a prime generator, you will cause:
- Overload operation
- Faster engine wear
- Higher failure rate
- Shortened service life
Conclusion: Diesel Generators Will Remain Essential in the AI Era
As global demand for data processing increases with 5G, AI, IoT, and cloud computing, the reliability of power infrastructure becomes more critical. Diesel generators:
✔ Provide long-term, stable backup power
✔ Are indispensable for data centers
✔ Will continue to evolve with digital infrastructure
✔ Remain the “electrical guardian” behind modern computing
Understanding their classification, function, and technical structure helps enterprises make the right investment and ensures the reliability and safety of mission-critical operations.
What diesel generator are suit to data center?
In my opinion, high-quality brands include
