Power’s out. Job site’s live. The last thing you want is a generator that won’t start, isn’t strong enough, or burns out in a month.

The problem is, choosing the right one isn’t always easy. Between oversold specs, confusing kVA ratings, and 500+ models on the market - it’s hard to know what’s actually right for you.

This guide cuts through the noise.

It’s built from years of boots-on-ground experience by Shan, one of Blue Diamond’s longest-serving techs (and a licensed sparkie) who’s helped thousands of Aussies avoid expensive mistakes over the years.

If you want plain-English advice that tells you what matters, what doesn’t, and what to avoid, read on.

Step 1: Know What You're Powering

Before thinking about brand or budget, make a list of everything you want to run.

•     Are you trying to back up a house during outages?
•     Are you running tools on a job site?
•     Is it for a food truck, farm, or event setup?

"The first question I always ask is: what are you plugging in? If they say ‘just the fridge and some lights,’ we’re in the small portable range. If they start listing welders, compressors or coffee machines, it’s a different ball game." - Shan

Break down your list into two columns:

•     Essential items you must run (e.g. fridge, lights, water pump)
•     Optional items you’d like to have (e.g. microwave, aircon, pool pump)

Step 2: Understand Power Requirements

Each appliance or tool draws a certain amount of power, usually measured in watts (W) or kilovolt-amperes (kVA).

"The most common mistake I see? People don’t account for startup load — things like fridges or pumps can draw two or three times more power when they kick in."

How to Estimate:

1. Add up the wattage of everything essential
2. Allow a 30–50% buffer for startup or surge loads
3. Convert to kVA (if needed) using:
   kVA = Watts ÷ 0.8

“Let’s say your essentials draw 3000W. You’re really after a 4kVA unit minimum. Go smaller and you’ll be chasing problems.” — Shan

We strongly recommend speaking to our team or using a structured sizing tool to avoid under-powering or over-capitalising on your generator.

Step 3: Match Features to Your Use Case

Depending on how and where you’ll use it, look for:

•     Auto start (for homes with automatic transfer switches)
•     Wheels and handles (for portability)
•     Long run-time tanks (for remote sites)
•     Weatherproofing (for outdoor or coastal setups)
•     Low-noise models (for events or residential)

“We had a builder call us after his genny got bogged and flooded onsite. Turns out, it was never rated for outdoors. You’d be amazed how often it happens.”

Step 4: Choose the Right Generator Type

Now that you know how much power you need, choose a type:

Portable Generators

Portable generators are ideal for light-duty use and situations where mobility matters.

•     Great for tradies with smaller tool loads, food trucks, caravans, or emergency home backup
•     Easy to move, store, and set up
•     Common sizes: 2–8 kVA
•     Typically petrol-powered

“These are for those who just want to run some lights and drills. Not daily flogging — more like backup or quick setups.” — Shan

That said, if you plan to run a portable generator every day or under heavy load, it’s worth stepping up to a more robust diesel model from our mid-range tier.

Diesel Stationary Generators

Diesel generators are ideal for house backup, rural properties, trades, events, and industrial sites. They last longer, run more efficiently under load, and are safer for large setups.

At Blue Diamond, our diesel range is grouped into three tiers — depending on your budget, use case, and required features:

Tier 1 - Price Fighters: Standby/Trade Range

•     Engines: Chinese-made, generic Yanmar copies
•     Use case: Light tradie work, budget-conscious buyers
•     Pros: Affordable, gets the job done for light use
•     Cons: No-name alternators, basic controllers, not built for heavy daily loads

“These are for blokes who just want to run some lights and drills. Not daily flogging — more like backup or quick setups.” — Shan

Tier 2: Mid-Range Workhorse

•     Engines: Kohler, some Kubota models
•     Alternators: Rewindable
•     Controllers: Deep Sea or ComAp entry-level
•     Use case: Tradies, farms, regular site work, backup power
•     Pros: Reliable, affordable, better build quality
•     Ideal for: Daily use without spec-driven needs

“This is the sweet spot for most tradies and small businesses — good kit without going overboard.” — Shan

Tier 3: Premium / Spec-Driven Industrial

•     Engines: Perkins, Cummins, Kubota, Denyo
•     Alternators: High-spec, fully rewindable
•     Controllers: Deep Sea with remote monitoring
•     Use case: Mining, hire fleets, commercial builds, events
•     Features: Silenced canopy, bunded fuel tanks, 3-phase, RCDs

“If you’re speccing for mining, film shoots, or commercial installs — we’re talking Cummins, Perkins, Denyo. It’s all about reliability, quietness, and safety.” — Shan

Inverter Generators

Inverter generators are the go-to for sensitive electronics and ultra-quiet performance.

•     Best for caravans, laptops, point-of-sale systems, AV gear, or coffee machines
•     Output is stable, clean sine wave — won’t fry circuit boards
•     Lightweight and quiet — often under 60 dB
•     Usually petrol-powered, 2–3 kVA range

“If you're plugging into a coffee machine, go inverter or clean power. I’ve seen standard gensets fry boards — especially with newer appliances.” — Shan

Step 5: Choose the Right Supplier - Not Just the Right Generator

“Anyone can sell you a genset. The real difference is what happens when something goes wrong. Do they have the parts? Can they fix it? That’s where people get stuck and where costs can really add up.” — Shan

When you’re investing in power equipment, especially diesel units, make sure your supplier:

•     Stocks spare parts for the brands they sell
•     Has a national service network (not just a head office number)
•     Can offer warranty support without sending you back to the manufacturer
•     Knows what they’re talking about — and can walk you through an issue fast

At Blue Diamond, we:

•     Keep thousands of parts in stock (AVRs, solenoids, controllers, alternators)
•     Run an in-house service team with field techs and remote support
•     Know our gear inside-out because we assemble and test them ourselves

“We’ve had people call us in a panic after buying off eBay or a ‘mate’s mate’. The unit breaks down and no one can help. That’s why we back what we sell.”

Parting Tip From Shan

"A lot of issues come down to asking the right questions. I always say: if you size it right the first time, you avoid 90% of the dramas."

Need Help Sizing Your Generator?

Still not sure? Give us a call. Our team has seen it all — and we’ll walk you through it like Shan would.

We’ll help you:

•     Match the right model to your job
•     Avoid under-sizing and future faults
•     Find in-stock options that ship fast

Prefer to browse? Check out our full range of generators here.