Generator Buying Guide: Finding the Right One for the Job

To help you choose the most appropriate generator, we've put together this quick guide covering the different types, common applications and some of the key buying factors.

What generator type do I need?

Generators work by converting mechanical energy into electric energy and can be used for backup or prime power, depending on situation and need.

There are generators on the market to suit a wide range of uses – including home/residential, travel, retail, hospitality, trades work, farming, mining and more. They typically fall into four categories –inverter recreational, portable trade, home and backup, and large stationary. 

The type you need depends on your situation and power needs.

Inverter recreational generators

These are quiet compact units and the smallest in the range. 

Since these generators use inverter technology which responds to load, they produce a very clean voltage. 

This makes them well-suited to powering sensitive electronics like phones, laptops and televisions. Inverter technology also helps to make these units energy efficient.

Some typical uses for inverter generators include:

• On camping, boating and fishing trips.
• For caravans and motorhomes.
• As a small domestic backup power source during blackouts.
• For small events and mobile businesses such as food vans.

So, you might choose an inverter generator for the following:

• You are going caravanning next summer and want to be able to quietly run some appliances (e.g. air conditioner and fridge) and to charge mobile phones.
• You run a mobile coffee business and need a reliable power source in order to reliably serve your customers.
• For garden lighting for a 21^st birthday party.

Portable trade generators

As the name suggests, this type of generator is suitable for trades and can be carried from job to job. 

They typically come with steel rollover frames and condenser-style alternators, making them robust and reliable units ideal for an on-site power source where heavy loads are involved. 

They can be either  single phase or 3-phase to suit a wide range of situations and power needs.

Petrol units are great for general trade use while diesel units are well-suited for larger trade and mining sites. 

Some units also come with  silenced canopies which extra offer protection and security as well as quieter operation.

Some typical uses for portable trade generators include:

• On building and construction sites and mining sites.
• As a power source for equipment and tools and for factory maintenance.
• For use on farms and in agribusinesses.
• On off-grid properties as a backup.
• As a backup generator for home use.

You might choose a portable generator for the following:

• Trade work on building sites which requires a reliable portable power source for each one.
• You live off-grid and need reliable power or backup for a solar battery.
• For powering tools in your tool shed or workshop.

Home and backup generators

These generators are ideal for providing power to households or small businesses during outages. Having one of these units on-hand during a planned or unplanned outage could prevent you having to shut your business down for the day or throw out a lot of spoiled food from your home fridge and freezer!

Home and backup generators are typically powered by gas and propane – affordable, readily-available, and relatively clean and efficient fuels. Gas generators can be connected to mains gas or operated using bottled LP gas if mains gas is not available.

Common types in this category include single or three phase generators – such as those in the  Generac and similar ranges. These units are designed to handle extended run times in extreme conditions (e.g. high temperatures). They also come with automatic switching which senses outages and switches the unit on automatically to deliver the power you need within seconds. The power is then switched off when the mains power returns – whether this a matter of minutes, days or weeks.

Other types of generators can also be used for home backup power – especially when they have automatic switching. For example, a separate automatic transfer switch can be linked up to a regular standby generator if required in case of mains failure.

Uses for home and backup generators:

• Providing standby / emergency backup / temporary power for selected appliances and lighting in residential properties.
• For properties that are prone to outages or are in remote areas.
• For small businesses to keep equipment running when the power goes down (e.g. computer system and other business equipment).
• As a backup source for an off-grid solar power system.

Therefore you might decide on a home generator if:

• Your area suffers several outages every year and you want a backup power source.
• You want a backup source for your small business in case of outages or disconnections.
• You have a solar storage battery and would like an extra source for backup.
• Your business runs a small satellite office in a regional location and needs a backup source of power.

Stationary and large diesel generators

These are large commercial generators designed for backup power during outages, remote businesses that operate off-grid or large events.

This type of generator suits situations where a portable generator would not be sufficient for the power level the job requires.

Due to the size and weight of this equipment, a crane or forklift is required if the generator needs to be moved. However, these generators are typically stationary for long duration's before being moved, for example from one mining site to another or at the end of a festival or carnival. Commercial businesses might also hire these units for extended job requirements.

Large stationary diesel generators operate on  3-phase power. Unlike single phase which only uses only one wire, 3-phase operates using three wires which essentially means extra loads can be added. This makes 3-phase generators well-suited to jobs that require delivery of larger power loads.

Generators in this category are rated for prime power or for standby power. 

Prime power equipment best suits situations where mains power is not available (e.g. remote mining sites). Standby power however refers to the supply of emergency power for a limited period, such as during outages. Standby power rated generators should not be run while mains power is operating.

Stationary generator uses:

• Mining and other sites that require prime power.
• For standby power in data sites and big high-rise offices.
• On farms and agricultural properties.
• In supermarkets, restaurants and shopping centres for backup power in outages.
• For large events, and for use in council or other government buildings.

So this means you might purchase a large commercial diesel generator for the following situations:

• Where you need a continuous power source on a remote mining site.
• If you run several large-scale events during the year.
• For a data site that operates continuously and needs emergency power in blackouts.
• For a large office or factory setup that needs to continue operating during outages.
• For emergency backup power in high-rise buildings and apartment complexes.
• For use on your agricultural property.

Diesel or petrol generators – which one to use?

Both diesel and petrol offer benefits, and which one to use depends on a range of factors.

For example,  diesel generators might cost more than petrol generators, but at the same time it is more efficient in usage, less volatile and it operates at a lower temperature. 

These factors can lead to cost-effectiveness, safety and reduced wear and tear on equipment.

Therefore, diesel generators may best suit the following situations:

• Large-scale ongoing commercial operations where high fuel efficiency is required.
• For heavy commercial or industrial use where power demands are high.
• Industrial situations where noise is not an issue (although noise can be offset by using a generator that is enclosed in a canopy).
• Where the equipment is needed to last for a long time.

While petrol is more volatile than diesel, petrol generators often come with in-built safety features that can offset this risk. They are also often quieter and cheaper to buy than their diesel counterparts and may come with additional features to improve efficiency.

So, petrol generators may suit situations where:

• Infrequent or smaller-scale use is required.
• Where quieter, low-noise operation is important – such as in a residential area.
• For domestic, household and small-scale trade use as opposed to large-scale industrial situations.

So, as for other factors, which type of fuel is best will really depend on the individual situation.

What features should I look out for in a generator?

Here are some features to look for, depending on what you're planning to use the generator for.

• Noise rating – generators come with a decibel rating. If you want quiet performance look for a unit that operates at 60 decibels or below. Some generators come with noise reducing features as well (e.g. a silenced canopy).
• Health and safety – e.g. look for features like fuel manual shutoff switch, auto-shutoff, RCD, earth leakage protection and weatherproofing. For a worksite you will need a WorkSafe Approved generator.
• Portability – look for generators that are lightweight or at least easy to manage. Helpful features include lifting bars and wheel & handling kits.
• Fuel capacity – it’s important your generator can run tasks without constant topping up. For this, look at the tank capacity and usage-per-hour in litres.
• Starting mechanism – examples include electric key or push-button, remote start, or auto-start where you need your generator to kick in immediately in an outage.
• Power output (kVA) – your generator needs to be able to power all the appliances and equipment you intend to use it for. See below under Section 4 for more detail on this and on how to convert wattage to kVA.
• Automatic Voltage Regulator (AVR) feature – this enables more stability of output and compensates for voltage load variations, making it good for powering sensitive equipment.
• Automatic Transfer Switch (ATS) – this feature enables the generator to quickly kick-in automatically in a mains power failure.
• Cooling system – this can be either air or water. Air-cooled systems use fan-forced air to cool engines and are best suited for domestic generator use. Water-cooled systems are more powerful and better suited for large homes, businesses or commercial offices.
• Single or 3 phase – single phase (single wire) is more suited to domestic homes and small business, whereas 3 phase suits larger commercial operations that require additional power boosts.
• Brand name & quality – this depends on budget and requirements. For example, budget brands can suit light use, but may come with less sales support compared to premium brands like  Denyo, Honda, Cummins, Perkins, Kubota.

What size generator do I need?

There are a couple of things to consider here.

• What appliances do you want to run using your generator? You will need to know the power requirements of each in watts. This includes both start-up and continuous running wattages (these will be the same in some cases but not others). For some appliances, the starting requirement can be up to four times greater than the running output. This typically applies to items with a motor or heat element. This includes refrigerators, air conditioners, electric fryers, toasters, coffee machines, hair dryers, drills, saws, and grinders.
• How many appliances do you intend running at any one time? If there are several you will need to add up the power needs of all of them to arrive at a total.

Calculating the power needs of your appliances in this way will give you a good idea of the size of the generator you require. For example, if your power needs come to 2,100 watts (2.1 kW), you should look for a generator with a capacity of at least this amount.

You can find wattage information on the product data plate or in the user manual. If this is unavailable, other options include contacting the manufacturer, using a wattage meter or calling in an electrician to take readings.

However, generators are often described in terms of kVA (kilovolt-ampere). To convert kW to kVA you will need to divide it by the generator power factor. For a Generac home generator for example, which have a power factor of 1, you would need a 4kVA unit to meet a requirement of 4kW (4 divided by 1).

The following provides a general guide to generator sizes for different requirements:

• Caravan air conditioner – recreational inverter generator of approximate size 2-3 kVA (but depends on the age and wattage use of the appliance).
• Essential household items – domestic backup generator of 5-10 kVA (depending on wattage of appliances)
• Full-size, average home – home backup generator of approximate size 18-20kVA (based on an estimated Australian daily household use of 18kW).
• Low-mid trade equipment – portable trade generator of 5-50 kVA.
• Large commercial sites – stationary diesel generator of 50-700 kVA.

The above are ballparks only. For generator-sizing help for your particular application, you can contact us on  1300 890 261.

How much do generators cost?

Generators can range from under $1,000 for small recreational models up to hundreds of thousands of dollars for big commercial units.

Here is a rough price guide:

Recreational:

Prices range from about $800 to $7,000 (1-7 KVA). The lowest cost recreational generators are smaller and with lower capacity than those with higher prices. You will also pay more for premium brands such as Yamaha and Honda.

Home & backup:

Around $7,000 to $14,000 (8-20 KVA). Differences between the lowest and highest cost units include capacity, size and power phase (e.g. single phase vs 3 phase).

Portable trade:

Range from around $1,000 to $21,000 (2-12 KVA). Some key differences between the lowest and highest cost units include fuel (petrol vs diesel) and starting mechanism (key vs auto). The higher priced units also come with canopy enclosure and water cooling.

Stationary diesel:

Approximately $5,000 to $450,000 (10-11,000 KVA). Some of the differences between lowest and highest priced units include standby power (10 kVA vs 1,200 kVA), power phase (single vs 3 phase), and fuel tank (30L vs 600L).

Where should I buy a generator?

Look for reputable suppliers and service agents that will offer you expert advice and ongoing support. Also look at what guarantees and extended warranties the company offers.

Check out our range at Blue Diamond. We stock generators to suit a wide range of applications and budgets – from recreational and home use through to robust machines for mining sites. Get in touch with us to find out how we can help you find the right generator, Australia-wide.