How Do Diesel Generators Work

Diesel generators convert the energy in diesel fuel into electricity. They operate in a slightly different way to other types of generators. Let's look at how diesel generators work, what they are used for and why you should choose to buy one.

How do diesel generators work?

Diesel generators use a series of steps to generate AC (alternating current) electricity. The process starts when a diesel (combustion) engine converts some of the chemical energy in the fuel to rotating mechanical energy. The rotating motor is then used by the AC alternator to generate electricity, while a wire moving through a magnetic field induces electrical charges. This type of generator can be used for either prime or standby power. For example, a diesel generator might be used for prime power in a remote region with limited grid connection, or for standby or backup power during a blackout.

There are two ‘types’ of machines, so to speak. They can either be single-phase which could suit household or small business use, or three-phase for longer-term or heavy-duty industrial use. Generators should not be used concurrently with mains power, which is why they often come fitted with a transfer switch to prevent this from happening.

Why would you choose a diesel generator?

Why would you choose a diesel generator?

Diesel generators come with a range of benefits. These include robustness, good longevity, relatively low maintenance needs, high efficiency and safety. Diesel generators suit several types of scenarios:

  • Tradespeople that need a portable generator to use on work sites.
  • People who live off-grid and need reliable power source.
  • As a backup for a solar battery.
  • For use at large-scale events.
  • For farm and agricultural use.
  • As a continuous power source on a remote mining site.
  • For large businesses, warehouses or health services that operate continuously and need an emergency power source in case of outages.
  • In shopping centres or supermarkets in case of grid-power loss.

Essentially, a diesel generator could enable you to keep your home, business, or essential service functioning during outages. You could also use one as a prime source of power if required.

How efficient are diesel generators? How long do diesel generators last?

Diesel engines use compression heat rather than spark ignition to burn the fuel and have greater thermal efficiency than other types of internal combustion engines. This makes diesel generators very efficient machines, especially for continuous and heavy duty use. As a general rule, diesel generators will use 0.4lt of fuel for each kWh produced, which equates to an efficiency ratio of 25%. The efficiency of any particular diesel generator however will depend on the situation and how it’s used. Diesel generators are generally very long-lasting, as they suffer less wear and tear than petrol-run models.

Diesel vs petrol generators: which is better?

Diesel vs petrol generators: which is better?

Benefits of diesel generators

At face value, diesel offers several advantages over petrol. For example, diesel generators are more efficient in that they require as little as half as much fuel and don’t need to work as hard as petrol units to produce the same output. So, while diesel costs more per litre, a diesel generator will use less fuel which can mean lower costs over time. Diesel is also less volatile than petrol, making it safer to use. And because a diesel machine runs cooler than one run on petrol, and doesn’t need to work as hard, its maintenance requirements are lower.

Benefits of petrol generators

On the other hand, there is a wider range of petrol generators on the market, and petrol models generally cost less to buy. Petrol is also less polluting than diesel as it produces fewer emissions. That said, a diesel generator requires less fuel which can equate to lower pollution overall. The differences between the two types are also narrowing. For example, many newer petrol models come with built-in safety features, offsetting their higher safety risk. Also, while diesel generators are noisier, some models now come with noise-reduction features.

So which is best?

The answer really depends on why you want a generator. For short-term or intermittent use, you are unlikely to experience the cost-saving and efficiency benefits of diesel. This means if it’s a generator for modest use, such as a back-up or occasional power source, petrol would probably be your best bet. For high-use or heavy industry situations, diesel works out better in terms of long-term efficiencies.

What size diesel generator do I need?

Diesel generators come in a variety of types and sizes. This includes portable models from 6kVA to 11kVA through to 3-phase stationery generators up to 2,000 kVA or even larger. You might choose a portable generator for trade, farm or home and back-up use. For intensive and continued use, you may need a large 3-phase stationary model. To work out the right size, you need to consider:

  • The power needs of the appliances or machines you want to run in terms of wattage, for both running and start-up.
  • Whether you intend running several pieces of equipment at the same time. If so, you will need to add up the requirements of each to arrive at a total.
  • Converting the wattage requirements to kVA. This is done by dividing the kW requirements by the generator power output factor (usually 0.8). So, for requirements of 7kW and a power factor of 0.8, you would need a generator of at least 8.75 kVA (7 divided by 0.8). Once you have an idea of your size requirements, get in touch with our team to discuss the best generators to match your needs.

How much do diesel generators cost?

There are diesel generators to suit a range of budgets.

Portable diesel generators start at around $1,800 for a 6kVA unit through to $21,000 for 11kVA.

Larger diesel generators can range from $22,000 to $320,000 depending on size and features.

Is there anything else to consider?

Look for diesel generators from reputable suppliers with service agents, and that come with good warranties. This includes the option for warranty extensions.

Here at Gogopower Australia, we stock quality diesel generators in a very large range of sizes and types. For advice on quality diesel generators for your home, commercial, or essential service needs, please contact us at