Skip to content
Click Here Sales !!!!
Click Here Sales !!!!
Diesel or Petrol Generators: The Ultimate Showdown

Diesel or Petrol Generators: The Ultimate Showdown

G’day readers! Robert here, your resident generator expert at Generator Warehouse. Today, I’ll provide a detailed comparison of diesel and petrol-powered generators to help you determine which is better suited to your needs. Having worked with these machines for over a decade, I can offer practical insights from experience alongside technical know-how from my engineering background. Buckle up as we delve into the key factors that set these generator types apart!

How Do Generators Work?

Before comparing diesel and patrol units, it helps to understand the essential components that make up a generator:

  • Engine - Provides mechanical power to spin electromagnets within the alternator/stator
  • Fuel System - Supplies the machine with diesel or petrol to operate
  • Alternator - Produces electrical current when its electromagnetic coils are rotated
  • Control Panel - Enables monitoring and regulation of electrical output

The engine turns a rotor inside the alternator, which induces a magnetic field that pushes electrons along the stator windings, generating electricity via electromagnetic induction. So without fuel, the engine would not run, and no power gets created!

Petrol Generator

Diesel Generator Advantages

Having supplied many diesel generators to commercial clients over the years, their extreme reliability and efficiency stand out. Here’s why diesel generators have proven invaluable, especially for industrial use:

Fuel Efficiency

The high compression in diesel combustion gives it a fundamental edge in fuel efficiency - diesel contains about 15% more energy per litre than petrol. Unlike petrol generators, diesel generators consume less fuel and are designed for continuous operation.

Greater economy means lower operating costs in the long run, which is hugely beneficial for warehouses, construction sites and remote facilities. Diesel is a more cost-effective option for heavy, sustained use.

Robust Construction

A sturdy build is integral to coping with extreme conditions - something I’ve seen diesel generators handle with aplomb. Components like the engine block, fuel tank and supporting frame are made of durable materials to withstand harsh weather, dust and dirt.

When maintained correctly, the average diesel generator has an operational life spanning 15,000-30,000 hours. Now, that sort of longevity and reliability inspires confidence in buyers!

Power and Load Capacity

This is where diesel generators excel - their innate ability to sustain heavy electrical loads without destabilisation. Diesel engines produce a broad torque range to support voltage stability as appliances switch on/off intermittently.

Commercial units can deliver power outputs between 25kVA and 2000kVA. Whether you need to power an entire factory or just emergency lighting, a robust diesel generator is suited to the task.

Of course, higher power output means a larger generator unit overall. Portability does decrease for industrial-scale models. But when an uninterrupted power supply is critical, diesel generators will rise to the challenge!

Petrol Generator Benefits

While diesel generators better meet severe power demands, don’t count your average petrol generator out yet! Running costs aside, they offer unique advantages that make them a versatile backup option:

Lower Emissions

This is an essential factor for environmentally conscious buyers. Petrol contains less carbon than diesel - burning petrol produces 20-30% less greenhouse gas emissions per kWh. While not zero-emission, petrol generators are comparatively cleaner.

Many residential areas enforce emissions regulations, too. So petrol generators neatly sidestep any legislative issues that commercial gensets might face around pollution. Going green, indeed, does seem more straightforward!

Compact Size

One aspect of petrol generators that continually impresses is how portable even mid-range models are. A single person can lift units rated 2-5kVA without difficulty. Couple that with wheels and telescopic handles and an easily moveable backup supply.

Meeting short-term rural or outdoor power needs becomes more feasible. Petrol generators shape up nicely for flexible applications where small footprints and quick deployment matter.

Affordable Costs

Let’s face it: Price significantly influences consumers' purchase decisions. And petrol generators are significantly cheaper upfront - a mainstream 5kVA diesel genset can cost three times more than an equivalently rated petrol variant!

Yes, there are long-term fuel efficiencies that offset diesel generator costs. But if budget constraints dominate, petrol generators make the grade an inexpensive backup choice. Installation costs are lower, too, owing to a smaller footprint and components overall.

Key Comparison Factors

We’ve covered some distinct advantages that diesel and petrol generators present. Now, to examine key metrics and how they stack up against each other:




Power Density



Fuel Efficiency

More efficient

Less efficient

Output Stability










15,000-20,000 hours

1,000-3,000 hours*


Bulkier models

Compact forms available


Higher initial cost

Lower initial cost

* Regular maintenance improves petrol generator lifespans

It’s pretty clear that diesel generators excel in fuel efficiency, heavy load capacities and overall robustness. They are a powerhouse solution for industrial settings.

On the other hand, petrol generators shine in aspects like lower emissions, affordable pricing and transportable sizes for domestic/recreational use. Different target applications.

Diesel generators aren’t optimally designed for low electrical loads despite higher efficiency - engine knocking can occur. So petrol units operated at 30-70% rated capacity tend to offer better runtime value. Purpose matters!

Diesel Generator

Making the Optimal Choice

We’ve covered plenty of technical ground comparing diesel and petrol models. But which is ultimately better for your situation? Here are vital questions to ask yourself:

  • What applications will the generator be used for?
  • What type of load will the generator need to handle?
  • How portable does it need to be? Any noise or emission restrictions?
  • What is the required backup runtime, i.e. how long must it supply power?
  • What level of monitoring/control functionality is essential?
  • What is my overall budget for purchasing and maintaining it?

The answers will clarify whether a diesel or petrol generator is more practical. Of course, an expert can swiftly narrow it down, too!

Diesel vs Petrol - The Verdict?

Let’s recap the critical comparative points:

Diesel Generators:

  • Extreme durability with lifespans from 15,000-20,000 hours
  • Excellent fuel efficiency results in lower long-term running costs
  • Higher power densities suit constant industrial loads up to 2000kVA
  • Generally cost more upfront owing to advanced components

Petrol Generators:

  • Greener and cleaner with lower emissions compared to diesel
  • Compact size with excellent portability for domestic/leisure use
  • Cheaper to purchase initially but less fuel efficient overall
  • Lower noise levels make them suburb-friendly

In essence, diesel generators provide hardened reliability and efficiency for industrial power supply. Petrol generators present a handy, cost-effective backup solution for versatile domestic/SMB needs.

But there are always exceptions! Hybrid bi-fuel generators allow switching between diesel and natural gas-powered operation. Small portable diesel generators exist for RV travellers, too. And petrol generators running on LPG give better efficiency alongside lower emissions.

The core basics remain the same - heavy-duty backup calls for diesel, while petrol answers residential demands. But do enquire if unique needs demand an unconventional solution!

Diesel Generator Components

I get a lot of queries about what constitutes a complete diesel genset package. Here is an overview of critical diesel generator components integrated into a functioning diesel generator system:

  • Engine - Heart of the generator. Popular engines used include Perkins, Volvo Penta and Cummins, which give tested reliability for the end product.
  • Alternator - Usually a brushless, revolving field alternator that produces the electrical output. Available in synchronous, asynchronous and permanent magnet options.
  • Fuel Tank - Storage for diesel fuel supply. Generally, in-built fuel tanks offer capacities from 25L to 2500L depending on generator size and expected running hours.
  • Batteries - Typically, two starter batteries are connected in series to provide the required cranking power for genset ignition. Maintenance-free batteries are now commonly opted for.
  • Control Panel - Sophisticated modules offered by DeepSea, Datakom and ComAp bring advanced monitoring, voltage regulation and safety functionalities. Remote control, auto start and auto transfer features are also integrated.
  • Enclosure/Canopy - Weatherproof metal housing critical for protection from dust, debris and extreme temperatures. They are manufactured from steel, aluminium or composites. It also reduces genset noise emission. Wind rating matched to operating environment conditions.
  • Base Frame - Structural base frame with anti-vibration mounts for stable generator mounting. Allows convenient forklift access when loading or relocating the generator.

Right-Sizing Your Diesel Generators

Another critical question I often get asked is how to accurately size a diesel generator for the intended application. Some quick rules of thumb to follow:

  • For continuous standby power needs, size your generator to handle 60-70% of total load demand to allow a safe operating margin. This avoids overload issues.
  • When the generator only sees periodic use, an alternator sized for 80-100% peak load is recommended for optimal efficiency. Just ensure runtime is within rated capacity.
  • Industrial generators may require N+1 redundancy, i.e. installing multiple smaller gensets so that load can be easily switched across units for maintenance rotations. 50% redundancy is commonly built-in.

More precise generator sizing calculations are based on parameters like site altitude, temperature variations, starting KVA motor loads, etc. But the above guidelines cover fundamentals nicely. Should questions arise during purchase, I remain only a call away!

Summing It Up

Phew, that was a comprehensive guide around comparing and selecting diesel or petrol-powered generators! To recap critical takeaways:

  • Diesel generators offer hardened reliability and efficiency for heavy-duty industrial loads
  • Petrol generators provide a compact, emitter-friendly power source for domestic backup purposes
  • Lifespan, fuel efficiency, emissions, noise, costs and portability differ across the variants
  • Accurately sizing generators for your application prevents underpowered or over-specced purchases

Do diesel or petrol generator queries? Still uncertain which is better suited for you? Reach out to the Generator Warehouse team for personalised advice! We offer tailored consultation and after-sales support, ensuring you invest in an optimally matched generator for lasting value.

Stay tuned for more posts sharing insider knowledge and technical nitty-gritty around power generators. Do you have any suggestions for topics I should cover? Let me know in the comments!

Previous article Inside a Diesel Generator: Uncovering Its Core Components
Next article Why Choose Diesel? Top Benefits of Diesel Generators Revealed