Diesel Generators
The industry workhorse — proven, low CAPEX, fast to start, but noisy, polluting and fossil-fuel dependent.
What Are Diesel Generators?
Diesel generators are the most widely used backup power technology today. A diesel engine drives an alternator to produce electricity when grid power fails. They have been deployed for decades in data centers, hospitals, telecom sites and industrial plants, and the supply chain, service network and operating experience are fully mature.
How It Works
When mains power fails, an automatic transfer switch (ATS) starts the generator. The diesel engine spins the alternator and reaches stable output typically within 10 to 30 seconds. Diesel fuel is stored on site in tanks, and runtime is limited only by fuel supply and maintenance intervals.
Key Specifications
| Parameter | Typical Value |
|---|---|
| Start-up time | 10–30 seconds |
| Response type | Seconds (not seamless) |
| Runtime | Hours to days (fuel-dependent) |
| CAPEX per MW | Low–medium (USD 300–700k) |
| Fuel cost | Medium–high, volatile |
| Emissions (CO2) | High (~0.85 kg CO2/kWh) |
| Noise | High (85–105 dB) |
| Lifespan | 20–30 years |
Advantages
- Lowest upfront cost per MW
- Proven technology with mature service networks
- Unlimited runtime with fuel supply
- Independent of grid or renewable sources
Disadvantages
- High CO2, NOx and particulate emissions
- Noise and vibration at sensitive sites
- Fuel storage, spill and fire risk
- Fuel degrades over time; needs testing and maintenance
- Not aligned with net-zero targets
Best-Fit Applications
- Sites where lowest first cost dominates decisions
- Long-duration outages without grid constraints
- Remote sites with diesel logistics in place
- Transitional backup while clean options mature
Market Notes
Major suppliers include Caterpillar, Cummins, Generac, Rolls-Royce (MTU) and Kohler. Many manufacturers now offer HVO (hydrotreated vegetable oil) capability to cut lifecycle CO2 without hardware changes.
FAQ
How fast does a diesel generator start?
Typical automatic start takes 10–30 seconds, so brief battery/UPS ride-through is still needed for seamless transition.
Can diesel generators run on cleaner fuel?
Yes — HVO or biodiesel can reduce lifecycle CO2 by up to 90% in many modern units with minor or no modification.
Are diesel generators being phased out?
Not immediately, but tightening emission rules and net-zero commitments are pushing operators toward hybrid and hydrogen alternatives.