Guide to Buying the Best Generator in NZ

When choosing the generator that's right for your house, farm, or business in New Zealand, there are several things to consider. Most importantly, you'll need to know the power requirements of the equipment you'll be running. It's easy to be intimidated by a barrage of technical electrical information, but this simple guide will help you make an informed and confident purchase.

1. Power output: Watts vs kVA

There are two primary power measurements for generators: startup watts (also referred to as peak power) and running watts.

You'll need to choose a model powerful enough to handle the startup wattage of your equipment. As a general rule, the startup wattage is approximately 2-3 times the running wattage. This varies, however, and your best bet is to check the manual of the device you're planning to power for an exact value.

At the bottom of this guide, we provide approximate running wattage values for common household appliances.

2. Fuel type: Petrol vs diesel

Most portable generators run on petrol. Diesel models are generally harder to start and slightly more expensive than petrol, but worth considering. They offer increased reliability and a longer life, especially under continuous use. For larger units, diesel is also more efficient and less expensive to run due to lower fuel costs.

We recommend using a conditioner with diesel fuel to stop fungal growth and prevent degradation of the unit’s quality (this happens naturally).

Browse Trade Tested’s petrol generators and diesel generators.

3. Backup: Stationary vs portable

If you're looking for reliable backup power, portability may not be a priority. Stationary generators provide numerous advantages, they’re typically quieter, easier to start, and more powerful than portable options. Plus, if they’re professionally hardwired into your system (don’t do this yourself!), there will be no mucking around with extension cords when the power is out.

For camping, motorhomes, marine use, farms, tradies, or general home use, a portable unit will likely suit your needs better. The biggest decision with portable generators is your preferred startup method: electric start or pull start.

4. Traditional vs inverter

Inverter generators are particularly suited to powering sensitive electronics, such as computers, TVs, and microwaves. They produce a clean, stable voltage, ensuring no harmful power surges. Traditional generators run at full motor speed regardless of actual power demand. Inverter generators, however, employ an efficient self-governing smart throttle system, adjusting engine speed as you turn on a light or appliance. This ensures fuel efficiency, quieter operation, smoother running, and improved reliability, making them ideal for a wide range of applications.

Browse Trade Tested’s digital inverter generators and traditional generators.

5. Single-phase vs three-phase

Single-phase generators produce power suitable for most common household appliances and small businesses. Larger commercial operations often require a three-phase unit due to higher power demands.

Three-phase generators can be run as single-phase, but the output will be about one-third of their full three-phase capability.

Power required for common appliances

The list below provides approximate running wattage values for common household appliances. Ensure your generator has sufficient power output to handle startup wattage (approximately 2-3 times these running wattage values):

Household appliances:

Clothes Dryer: 4000W

Dishwasher: 1200-3600W

Electric Oven: 2000W

Heater: 150-2000W

Microwave: 600-1500W

Toaster: 800-1500W

Electric Frying Pan: 1200W

Iron: 1000W

Hair Dryer: 1000W

Stove Range: 800W

Coffee Maker: 800W

Vacuum: 200-800W

Washing Machine: 500W

Fridge/Freezer: 200-700W

Television: 100-450W

Desktop computer + Monitor: 100-400W

Blender: 350W

Electric Blanket: 200W

Sewing Machine: 100W

Light Bulb: 18-60W

Laptop: 50W

Shaver: 15W

Outdoor power tools

Electric Mower: 1500W

10" Bench Saw: 1500W

Weed Eater: 500W

Hedge Trimmer: 450W

Belt Sander: 380W

Drill: 330W

When browsing generators at Trade Tested, you’ll see the capacities listed in kVA (kilo volt-amperes). This is standard practice in New Zealand (or outside the US). Specific wattage (both startup watts and running watts) details are listed in each model’s description on our site.

Choosing the wrong-sized generator is a common mistake. Most units sustain only 80% of their maximum power for the long haul. Constantly pushing a generator beyond 80% may shorten its life and risk damaging connected appliances. When in doubt, bigger is better.

Safety tips

Always consult your operator manual for a full list of safety precautions. Here are a few essential tips to support safe generator use:

Never run your generator indoors or in poorly ventilated areas. Keep it away from windows, doors, and openings to avoid exhaust entering your home.

Place the generator on a level surface.

Protect the unit from excessive moisture, dirt, and dust.

Avoid overfilling the fuel tank and never refuel the generator while it's running or still hot.

Keep the unit a safe distance from open flames, pilot lights, or anything sparky.

Never connect a generator directly to your house’s wiring without a professionally installed transfer switch.

Use heavy-duty outdoor extension cords for plugging appliances into the generator, or connect it to a professionally installed power-transfer switch.

Do not overload the unit.

Ready to power up?

If you’re after a reliable backup power solution for your home, farm, or next camping trip, Trade Tested has all your generator needs covered. Browse our full range of generators from trusted brands; built for performance, reliability, and convenience. Got questions? Either send us an email or give us a bell during office hours on 0800 800 880.

What our customers say

“Very easy to assemble. Followed start up procedures and click brooooom. Fired up first pop.”

“Great generator for around the house. Unpacked it, connected the battery put oil and fuel in, started the first time, and runs like a dream.”

“Very good value for money. Very happy with purchase.”

Frequently asked questions

Where should I place my generator?

Operate it outdoors on a level surface, at least 5 to 6 metres from windows and doors to avoid exhaust intrusion. Provide at least 1.5 metres of clearance around it for airflow and servicing.

How often should I maintain my generator?

Check the unit before each use. Maintenance typically includes oil/air filter changes every 100 hours (gas) or 500 hours (diesel). Use quality diesel conditioner and disconnect spark plugs when servicing.

What accessories should I buy for my generator?

Key accessories include: transfer switch, heavy-duty outdoor extension cords, wheel kits, enclosures or storm covers, remote-start modules, parallel kits, and fuel conditioners.