How to Work out the right size generator

Posted by Mowercentre | 20th June 2019

When choosing a generator, size matters—but not just physically. We’re talking about power output. Picking the right size generator is all about understanding how many watts your appliances and tools actually use, so you don’t end up stuck in the dark—or worse, damaging your gear.

📊 Step 1: Work Out Your Power Needs

First things first—don’t rely solely on the wattage printed on your appliance. That number usually refers to how much power it outputs, not how much it actually consumes to operate.

💡 Example: A 900W microwave gives you 900W of cooking power—but will need more than 900W to run.

🔍 Step 2: Check the Appliance’s Data Tag

Look at the data plate or label on your appliance. It’ll usually show:

• Volts (V)
• Amps (A)
• Sometimes Watts (W), Horsepower (HP), or Hz (cycles)

If it lists Amps and Volts, use this simple formula:
Watts = Volts × Amps

⚠️ Step 3: Account for Starting Watts

Some devices—especially those with electric motors—need extra power to start. These include:

• Fridges & freezers
• Air conditioners
• Power tools
• Air compressors
• Bore pumps

These starting watts can be 2 to 3 times the regular running watts.

🧮 Step 4: Add It All Up

Let’s break it down with a quick example:

So, in this case, you’d need a generator that can handle at least 1,850 watts of continuous power.

🚨 Why It’s Important Not to Undersize

Getting a generator that’s too small can cause:

• Overloading
• Poor performance
• Damage to sensitive equipment
• Shortened generator lifespan

✅ Aim for Headroom

It’s smart to buy slightly more power than you actually need.

Here’s why:

• Most generators run best at 80% of their maximum capacity
• Running at max capacity for long periods reduces life span and efficiency

Pro Tip:
If your appliances need 1,850W, aim for a generator rated for 2,200W or more to give you that safety buffer.

Need Help?

Still unsure? Drop us a message or come in for a chat! We’re happy to help you calculate your power requirements and match you with the perfect generator for the job.

Whether it’s for work, travel, or home backup, we’ve got the right power solution for you.