What Size Generator for Home Do I Need? A Complete Sizing Guide
Choosing a home generator starts with the appliances you need to run, not the size of your house. Add the running wattage of the appliances you expect to use at the same time, then account for the extra power some motors need when starting. If a generator is rated in kVA, check its power factor and continuous output in kW before comparing it with your appliances. This guide explains how to estimate your load and choose a generator for your backup needs.
Why Generator Size Matters
Understanding how many watts to run house appliances is more than just a total wattage — it’s about understanding the difference between running power and starting surge. Getting it wrong can lead to multiple problems for Australian households:
System Shutdowns: Exceeding the generator’s capacity may trip circuit breakers, temporarily cutting power to connected appliances.
Appliance Startup Failures: Appliances with high inrush current, like AC units, refrigerators, and water pumps will fail to start or stall if the generator lacks surge capacity.
Voltage Instability: An undersized generator operating near its limit may cause temporary voltage drops, which can affect sensitive electronics like modems, smart TVs, and other home appliances.
Fuel Inefficiency: Generators running consistently far below or above their optimal load range may consume fuel less efficiently, reducing overall cost-effectiveness.
Reduced Lifespan: Chronic overloading or persistent low-load operation can increase engine wear, affecting long-term reliability and service life.
What Size Generator for Home: Key Factors
Household Energy Needs
Australian homes typically use 15–20 kWh of electricity per day, with single-person households averaging 8.65 kWh and larger families often requiring 18–23 kWh or more, depending on lifestyle and appliance usage. Knowing which appliances and circuits are essential during an outage helps set the baseline capacity your generator must cover.
Starting Surge Loads
Appliances such as air conditioners, refrigerators, and water pumps require higher power during startup than their normal running load. Sizing a generator only for running wattage can lead to overloads or shutdowns when these devices start. Allowing a 20–30% power buffer ensures reliable operation.
Regional Climate Differences
Electricity demand varies across Australia due to climate differences. Homes in warmer regions rely more heavily on cooling, while cooler areas use more electricity for heating. Heating and cooling can account for 20–50% of a household’s electricity use, meaning seasonal peaks must be considered when sizing a generator.
Safety Margin and Future Considerations
It’s wise to include a 20–25% buffer beyond your calculated load to handle temporary spikes, unanticipated devices, or future household expansions. This safety margin improves reliability and prolongs generator's lifespan.
What Does kVA Mean for a Home Generator?
Generators may list their output in kilovolt-amperes (kVA), while household appliances are usually labelled in watts or kilowatts (W or kW). These ratings are related, but they are not always equal. To estimate real power, multiply the generator’s kVA rating by its power factor:
kW = kVA × power factor
For example, a 12 kVA generator with a power factor of 0.8 works out to 9.6 kW of real power. This is a calculation example, not a guarantee of usable output. Check the generator’s nameplate or manufacturer specifications for its rated continuous output, power factor and starting capacity before choosing which appliances to run. Learn more about how to convert kVA to watts.
How to Measure What Size Generator for Home
If you’re wondering what size generator do I need for my home, the first step is understanding your essential power needs. Follow these core steps to choose a reliable generator for home backup.
Step 1: List Essential Devices
Make a list of the appliances and devices you need to keep running during a power outage. Use the table below as a reference for typical household power requirements:
Usage Area | Appliance | Approx. Running Wattage (W) | Approx. Starting Wattage (W) |
Kitchen | Bar Fridge | 180 | 600 |
Toaster | 800 | 1,200–1,600 | |
Coffee Maker | 1,200 | 1,200 | |
Household Kettle | 2,200–2,400 | 2,200–2,400 | |
Living/Entertainment | TV (46”) | 200 | 200 |
Laptop Computer | 250 | 250 | |
Desktop Computer | 300 | 300 | |
Portable Fan | 40 | 120 | |
Cooling/Heating | Refrigerator & Freezer | 550 | 1,300 |
Caravan Air-conditioning Units | 1,000–2,000 | 2,200–3,200 | |
Laundry/Cleaning | Washing Machine / Belt Sander / Vacuum Cleaner | See running wattage above | See starting wattage above |
Outdoor/Workshop | Electric Hand Drill (1/2”) | 700 | 1,000 |
Electric Chainsaw (14”, 1hp) | 1,100 | 1,100 | |
High Pressure Washer (1hp) | 1,200 | 3,600 |
Source: mygenerator
Note: the power usage can vary based on the appliance's settings, usage duration, and specific model & manufacturer specifications.
Step 2: Determine Total Running Power
Check Rated Power: Locate the Running wattage (W) on each appliance’s compliance label.
Identify Starting Power: Note which appliances have motors (e.g., fridges, ACs, pumps). These typically require a surge of 2–3 times their rated power to start.
Calculate Total Running Load: Sum the wattage of all devices you intend to operate simultaneously. This represents your base continuous power demand.
Example:
Refrigerator & Freezer: 550 W (Starting: 1,300 W)
Household Kettle: 2,400 W (Starting: 2,400 W)
Desktop Computer: 300 W (Starting: 300 W)
Portable Fan: 40 W (Starting: 120 W)
Caravan Air-conditioning Units: 2,000 W (Starting: 3,200 W)
Total Running Power: 550 + 2,400 + 300 + 40 + 2,000 = 5,290 W
Total Starting Power (Peak): 1,300 + 2,400 + 300 + 120 + 3,200 = 7,320 W
This calculation helps you figure out what size generator for home backup to cover all essential devices safely.
Step 3: Add a safety margin to running power
Choose a generator with 10–20% higher continuous output than your total running wattage to ensure reliable operation.
Example:
Total Running Power: 5,290 W
10% margin: 5,290 × 1.10 = 5,819 W
20% margin: 5,290 × 1.20 = 6,348 W
Recommended Generator Rating: 5,819-6,348 W
Once you’ve calculated your total running and starting power and added a safety margin, you can use these figures to select a generator that meets your household needs.
Recommended Generators for Households
While traditional petrol or diesel generators remain an option, many Australian homes now prefer modern, eco-friendly solutions.
Consider a portable power station—a modern, rechargeable battery system that offers flexible, portable power for your home.
For households that need to power essential appliances—fridges, lights, Wi‑Fi, and a few small devices, rechargeable units like the EcoFlow DELTA Pro 3 Portable Power Station deliver reliable power for everyday use.
For households seeking full-home backup power, the EcoFlow DELTA Pro Ultra Whole-home Backup Battery provides higher continuous output for running essential circuits. When paired with the EcoFlow Transfer Switch, it can safely connect to your home’s main electrical panel, allowing reliable backup for a complete household.
Check out the installation tutorial for guidance.
Quick Summary: What Size Generator for Home?
If a generator is rated in kVA, check its power factor and rated continuous output before comparing it with appliance wattage. The calculation below shows how kVA relates to kW at two example power factors.、
Generator rating | At power factor 1.0 | At power factor 0.8 |
|---|---|---|
5 kVA | 5 kW | 4 kW |
8 kVA | 8 kW | 6.4 kW |
12 kVA | 12 kW | 9.6 kW |
These are calculation examples, not guaranteed generator outputs. Check the generator’s rated continuous output, power factor and surge rating in the product specifications.
What Can a 12 kVA Generator Run?
A 12 kVA rating alone does not tell you exactly which appliances a generator can run. Its real power depends on the power factor and rated continuous output, and motor-driven appliances may need extra power to start.
For example, 12 kVA at a power factor of 0.8 works out to 9.6 kW. Use the generator’s published continuous and surge ratings to check whether your planned combination of appliances fits within its limits. Add the running loads you expect to use at the same time, then account for the starting requirements of appliances such as pumps, refrigerators or air conditioners.
Conclusion
Determining what size generator for home you need starts with calculating your total running and starting wattage. Use a safety margin and refer to typical Australian household profiles to choose a generator or portable power station that reliably meets your backup needs. With the right size, you can ensure uninterrupted power, protect sensitive electronics, and maintain household comfort during outages.
FAQ
What Is the 80% Rule for Generators?
the 80% rule for generators means you should size your generator so that your typical running load does not exceed about 80% of its rated continuous capacity. This ensures the generator runs efficiently, avoids overheating, and provides a safety buffer for appliance startup surges. Following this guideline helps prolong the generator’s lifespan and maintain stable power for household appliances.
What Can a 7500 Watt Generator Run in a House?
Certainly. A 7500-watt generator can power most essential household appliances during an outage. This includes but is not limited to refrigerators, water heaters, washing machines, televisions, and more. A 7500-watt (7.5-kilowatt) generator should provide sufficient power for most Australian homes. However, conducting a home energy audit is necessary to ensure this. It is the key piece of equipment for an ideal home backup power solution.
What Happens If My Generator is Too Small?
If the generator is too small, it may struggle to provide sufficient power for your essential appliances. When demand exceeds the generator's capacity, it may overheat, trip, or shut down automatically. This can also cause voltage drops, potentially damaging sensitive equipment like refrigerators, computers, or routers. In some cases, continuously running a small generator may cause the engine to overheat and shorten its lifespan.