What Size of Solar System Do I Need? 6.6kW vs 10kW vs 13kW Explained
- 11 hours ago
- 5 min read
If you're considering solar for your home or business, one of the most important decisions you'll face is choosing the right system size. Naturally, many people ask: what size solar system do I need?
While the question seems simple, the answer depends on several factors. Some homeowners assume that bigger is always better. Others prefer smaller systems to reduce upfront costs. However, solar works best when it is carefully matched to your energy needs — not simply installed at the largest or cheapest option available.
In this guide, we compare 6.6kW, 10kW, and 13kW systems to help you understand which size suits your lifestyle, property, and plans. More importantly, you’ll learn how choosing the right system size can maximise long-term savings.
Key Takeaways
The right system size depends on your energy habits and future needs.
A 6.6kW system suits many average Melbourne households.
A 10kW system supports growing families and higher daytime usage.
A 13kW system works best for high-consumption homes or small businesses.
Table of Contents
Why Solar System Size Matters
When homeowners ask what size solar system they need, many focus on upfront cost. However, system size has a greater impact on long-term savings than most people realise.
Solar panels generate electricity during daylight hours. Therefore, your daytime energy usage - — not just your quarterly bill — determines how effective your system will be.
For example:
A home using 18–22kWh per day may suit a 6.6kW system
A household using 25–35kWh daily may benefit more from a 10kW system
Larger homes using 40kWh or more may require 13kW
Solar delivers the best results when you use the energy as it’s produced.
Oversizing without a plan to use extra energy may reduce financial returns due to low export rates.
That’s why thoughtful system sizing matters. An experienced solar system designer will review your energy usage and consider your daily habits and plans. To work out what size system you need, find the Average Daily usage in kilowatts and divide it by the number of peak sunlight hours in Melbourne (which is 3). This will give you the right size system for your current usage.
How Much Power Does Your Home Use?
Before choosing between 6.6kW, 10kW, or 13kW, reviewing your electricity bill is the best starting point.
Look for:
Average daily usage (kWh)
Seasonal changes
Peak usage times
In Melbourne, typical household usage falls into these categories:
Small households: 15–20kWh/day
Medium families: 20–30kWh/day
Larger homes with pools or EVs: 35–45kWh/day
Future plans also play a role.
For example:
Electric vehicles
Battery storage
Home extensions
Switching to electric heating
Installing a slightly larger system today may prevent costly upgrades later.
6.6kW Solar System: Who Is It For?
A 6.6kW solar system remains the most popular residential option.
It offers an effective balance between affordability and performance.
Typical Output in Melbourne
24–28 kWh per day
8,500–10,000kWh annually
This output often covers a significant portion of daytime energy needs.
Best Suited For:
Average-sized homes
Families of 3–4
Homes without heavy electric heating
Households without EVs or pools
Properties with limited roof space
Typical Cost
A solar system without a battery, after rebates:
$5,500 – $7,000
For many households, a 6.6kW system reduces reliance on grid electricity and delivers strong savings.
10kW Solar System: Cost and Benefits
For homes with higher energy usage, a 10kW system can deliver greater long-term value.
Typical Output
35–42 kWh per day
12,000–15,000 kWh annually
This makes it ideal for households with increased daytime demand.
Best Suited For:
Larger families
Homes with electric hot water and heating
Properties with ducted heating or cooling
Work-from-home lifestyles
Households planning EV charging
Cost Range
A solar system without a battery after Solar Vic and STC rebates:
$7,500 – $12,500 plus
Although the upfront cost is higher, many Melbourne households reduce grid reliance by up to 60–80%.
Is 13kW Solar Worth It?
A 13kW system suits high-energy households or small commercial properties.
Expected Output
45–55 kWh per day
16,000–20,000kWh annually
Best Suited For:
Homes with pools or spas
Multiple air-conditioning systems
Electric heating
Electric vehicles
Large families
Home-based businesses
Estimated Cost
$10,000 – $20,000
Larger systems may face export limits. Therefore, pairing them with battery storage often improves value.
👉 Learn more about battery installation:
Planning for Future Energy Needs
Your future energy usage may matter more than your current usage.
Lifestyle changes such as:
EV ownership
Home office expansion
Electrification of appliances
can increase electricity demand.
Many Melbourne homeowners initially install smaller systems, only to upgrade later.
Planning helps avoid:
Additional installation costs
Lost savings
System expansion limitations
Roof Space and System Design
System size also depends on:
Available roof space
Panel orientation
Shading
Larger systems require more space and optimal placement.
An experienced Solar Designer and a professional site assessment ensure:
Efficient panel layout
Maximum performance
Long-term energy output
Modern high-efficiency panels can improve output even with a limited roof area.
Budget vs Long-Term Value
It’s natural to focus on upfront cost.
However, solar is a long-term investment.
Getting the right size system that meets your energy usage often:
Deliver greater bill reductions
Shorten payback periods
Provide higher lifetime savings
For example:
One Melbourne homeowner upgraded from 6.6kW to 10kW after purchasing an EV. As a result, they significantly reduced their grid usage.
Why Choose Energy Wired?
Choosing the right system size is just as important as choosing the right installer.
Energy Wired is a Melbourne-based solar specialist with years of experience.
What Sets Us Apart
SAA-accredited installers
Top-quality panels and inverters
Honest energy analysis and sizing advice
Transparent pricing
Custom system design to meet your current and future needs.
We recommend solar system sizes based on:
Actual usage data
Property layout
Future energy needs
👉 Request a free quote today:
Conclusion
Solar is not simply about installing panels — it’s about installing the right system for your home.
Whether you are considering a 6.6kW system, exploring 10kW, or evaluating a 13kW solution, the best choice depends on your energy usage today and tomorrow.
A tailored system ensures strong performance, meaningful savings, and long-term value.
If you're still wondering what size solar system I need, Energy Wired can help.
👉 Contact Energy Wired today for a personalised solar consultation and free quote.
About the Author:
Clifford Wigg is an Accredited Solar Designer and Installer with 15 years of experience in the solar industry and 24 years of experience in the electrical field. He is accredited in the design and installation of grid-connected photovoltaic (PV) systems, battery storage systems, and standalone (off-grid) power systems.
As the owner of Energy Wired, Cliff leads a team of highly trained electricians delivering high-quality workmanship across Victoria. Energy Wired specialises in customised system design, premium products, and long-term value for every customer.
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