Yellow and black generator on open grassy field under stormy sky

August 19, 2025

What Size Generator Do I Need for a Storm?

When the next big storm rolls in, the last thing you want is a generator that's undersized - or panic-buying one at the hardware store while everyone else is doing the same. So what size generator do you actually need for a storm? Short answer: at least 5kW for the essentials, or 8-10kW+ if you want to run the whole house. Read on for the full breakdown.

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Portable generator running outside a residential home during a storm.

Understanding Your Power Needs: What Wattage Do I Need for a Generator?

Before you can pick the right generator, you need to understand what you're actually trying to power. That means knowing the difference between running watts and starting watts.

Running Watts vs. Starting Watts: What You Need to Know

Every appliance has two power ratings: what it needs to keep running, and what it needs to kick into gear from a cold start.

Defining Running (Continuous) and Starting (Surge) Watts

Running watts are the steady power draw while an appliance is operating normally. Starting watts - sometimes called surge watts - are the higher burst of power needed to start motors or compressors.

A fridge might run at 150W but spike to 600W at startup. That spike matters when sizing your generator.

How to Calculate Your Total Wattage Needs for a Storm Generator

Make a list of everything you want to run and note both their running and starting wattage requirements.

Add up the running watts, then find the single appliance with the highest starting watts. Your generator needs to handle the total running load plus that largest starting surge - all at the same time.

What Size Generator for Storm? Calculating for Essential vs. Whole-Home

Sizing for Essential Loads Only: Fridge, Lights, Fans, Phone Charging

If you're just keeping the basics going during a power outage, a 3-5kW generator will usually cover it.

That gets you a fridge, a few lights, phone and laptop chargers, and maybe a fan. It won't run your air con or electric stove - but for short outages, it's often all you need.

Sizing for Comfort Loads: Air Conditioning, Water Heater, Appliances

Want to stay comfortable during an extended outage? You're looking at 7-10kW or more, depending on your air conditioning unit and how many rooms you want cooled or heated.

Electric hot water systems are also big draws - factor those in if they're important to you.

Sizing for Whole Home Power: When You Want Everything Running

Running an entire home takes serious wattage. Expect to need 10-20kW+, especially if you have ducted air con, electric cooking, or a pool pump.

This usually means looking at a standby generator rather than a portable one - though large portables can bridge the gap for many Australian homes.

Portable generator positioned on grass near a wooden fence during a storm.

What Can a 5000 Watt Generator Run? A Practical Breakdown for Storm Use

A 5kW generator is one of the most popular choices for storm backup in Australian homes. It's portable enough to store easily but powerful enough to handle the essentials - and then some.

Appliances a 5000 Watt Generator Can Run Simultaneously

Kitchen Essentials: Fridge and Microwave

Your fridge and freezer are the priority during any outage. A 5kW generator comfortably handles both, along with a microwave for heating meals - typically 800-1,500W each.

Lighting and Small Electronics (TV, Phone)

LED lighting uses minimal power, so you can keep most of the house lit without worrying. Throw in a TV and a few phone chargers - no drama.

Limitations: Window AC, Sump Pumps, etc.

A small window air conditioner is possible on a 5kW, but it'll be tight if you're running it alongside everything else.

Large sump pumps, ducted AC, or electric ovens will likely tip you over - keep those for a bigger unit.

What Will a 3000 Watt Generator Run? Smaller Storm Scenarios

A 3kW generator is enough to keep the fridge running, charge devices, run a few lights, and maybe a small fan. It's a solid choice for minimal outages.

Not great for power-hungry appliances - but if your main concern is food safety and staying connected, 3kW gets the job done.

Generator Sizing Chart for Storm: Quick Reference Guide

Here's a rough guide to common appliances and their wattage requirements:

Appliance	Running Watts	Starting Watts
Refrigerator	150-400W	400-1200W
Window AC (1 tonne)	900-1200W	2000-3500W
LED Lighting (10 lights)	100-200W	Same
TV (50 inch)	80-200W	Same
Microwave	600-1200W	Same
Sump Pump	750-1000W	1500-2500W
Electric Hot Water	3000-5000W	Same

Portable vs. Standby Generators for Storm Preparedness

Both types have a role to play. The right choice depends on how often storms hit your area, your budget, and how much power you need.

Portable Generators for Storm Use: Flexibility and Affordability

Pros: Cost, Ease of Use, No Permanent Installation

Portables are cheaper upfront and don't require permanent installation. You can move them, store them, and take them camping or to a job site between storms.

For many Australian homeowners, a quality portable generator is all they'll ever need for storm backup.

Cons: Manual Operation, Fuel Storage, Running Time

You need to set it up manually, which is no fun in the middle of a storm. Fuel storage can also be a challenge - petrol degrades over time.

Runtime is limited by tank size, so extended outages may require planning around refuelling.

Standby Generators for Storm Use: Automatic and Always Ready

Pros: Automatic Start, Permanent Power, No Manual Setup

Standby generators kick on automatically when power drops. You don't have to do a thing - perfect for when you're away or for medical equipment users.

They run on natural gas or LPG, so there's no fuel storage headache. Just set and forget.

Cons: Higher Cost, Installation Requirements

Standby units cost significantly more - often $5,000-$20,000+ installed. They require a licensed electrician and council permits in most areas.

For most households, that's a big investment - but for storm-prone regions, it pays off.

Two men in orange safety vests preparing a generator during a storm.

Fuel Type Considerations for Your Storm Generator

Petrol (Gasoline) Generators for Storm Backup

Petrol generators are the most common choice for Australian households. They're affordable, widely available, and easy to maintain - if you keep up with oil and fuel changes.

The downside: petrol can go stale in storage, so you'll need to either rotate it regularly or use fuel stabiliser.

Diesel Generators for Extended Storm Outages

Diesel is more fuel-efficient and better suited to extended run times. It also stores better than petrol, making it a great choice for storm preparedness.

Diesel units tend to be quieter than older petrol models, and the fuel economy means fewer trips to refill.

LPG/Gas Generators: Longer Shelf Life

LPG doesn't degrade like petrol, which is a major plus for emergency preparedness. If your generator sits idle for months between storms, LPG is worth considering.

Dual-fuel models give you the option to switch between petrol and LPG - great for flexibility.

Safety Tips for Running a Generator During a Storm

A generator in a storm is a powerful tool - but only if you use it safely. Carbon monoxide, electrocution, and fire are real risks.

Essential Safety Practices: Placement, Ventilation, Extension Cords

Keep It Outside and Away From Openings

Never run a generator indoors, in a garage, or under a covered patio. Carbon monoxide from the exhaust is colourless, odourless, and deadly - it builds up fast.

Keep it at least 6 metres from windows, doors, and vents.

Use Heavy-Duty Extension Cords

If you're connecting appliances via extension cords, use outdoor-rated, heavy-duty leads designed for generator use. Undersized cords can overheat and start fires.

Never Backfeed Power Into the Grid

If you want to power your home's circuits through your switchboard, you must use a properly installed transfer switch. Never "back-feed" through a power point - it's illegal and dangerous.

Fuel Safety During a Storm: Storage, Refuelling, and Spillage

Store fuel in approved containers in a cool, ventilated area well away from your home and the running generator.

Never refuel while the generator is running or still hot. Let it cool for at least 15 minutes before adding fuel.

Conclusion: Choosing the Right Generator for Storm Preparedness and Peace of Mind

When it comes to storm preparedness, the right generator size depends on what you need to power, how long you need it for, and your budget. For most Australian homes, a 5-8kW portable generator hits the sweet spot.

Plan ahead, store your fuel safely, and make sure your setup is legal and safe. Because the last thing you want during a wild storm is to be fumbling in the dark with an undersized generator - or no generator at all.