Solar Panel System Sizes Explained: 6.6kW, 10kW, 13kW - Which Is Right?

Understanding Solar Panel System Sizes in Australia

Solar system sizing is one of the most important decisions you’ll make when going solar - and one of the most confusing. Terms like “6.6kW” and “10kW” get thrown around, but what do they actually mean for your electricity bill, your roof, and your wallet?

This guide explains the most common residential solar system sizes available in Melbourne, what each one produces, and how to choose the right size for your household. As CEC Accredited installers and NETCC Approved Sellers, Carlin Co has designed and installed solar systems across Melbourne for years - we know what works in practice, not just on paper.

What Does “6.6kW” Actually Mean?

When we say a “6.6kW solar system,” we’re referring to the total capacity of the solar panels (measured in kilowatts peak, or kWp). This is the maximum power the panels can produce under ideal laboratory conditions (called Standard Test Conditions, or STC).

In the real world, your system won’t hit this peak very often - cloud cover, temperature, panel orientation, and shading all reduce output. A 6.6kW system in Melbourne will typically produce 22-28 kWh per day averaged across the year (more in summer, less in winter).

The other key number is the inverter size. Australian regulations allow panels up to 133% of the inverter’s capacity, which is why a 6.6kW panel array is commonly paired with a 5kW inverter - it’s the maximum panel capacity allowed with the most popular inverter size.

Common Solar System Sizes Compared

5kW System (Typically 5-5.5kW of Panels)

Daily production (Melbourne average): 17-22 kWh
Annual production: 6,200-8,000 kWh
Number of panels: 12-14 (depending on panel wattage)
Roof space needed: Approximately 20-24 m²
Cost range: $4,500-$7,000 installed
Best for: Small households (1-2 people), units or homes with limited roof space

A 5kW system is the entry point for meaningful solar savings. It will typically cover the daytime electricity usage of a small household and export surplus to the grid. For a couple or single person using 10-15 kWh per day, this size can eliminate most of your daytime electricity costs.

6.6kW System (Australia’s Most Popular)

Daily production (Melbourne average): 22-28 kWh
Annual production: 8,000-10,200 kWh
Number of panels: 15-17
Roof space needed: Approximately 26-30 m²
Cost range: $5,500-$8,500 installed
Best for: Average households (2-4 people), the best value “sweet spot”

The 6.6kW system is Australia’s bestseller for good reason. Paired with a 5kW inverter, it’s the maximum panel capacity within the most cost-effective inverter bracket and offers the best dollar-per-watt value. For a typical Melbourne family using 15-25 kWh per day, this system will cover most daytime usage and generate meaningful feed-in credits.

If you’re adding a home battery later, a 6.6kW system produces enough surplus to charge a 10 kWh battery on most days.

10kW System

Daily production (Melbourne average): 33-42 kWh
Annual production: 12,000-15,300 kWh
Number of panels: 23-26
Roof space needed: Approximately 40-46 m²
Cost range: $8,000-$13,000 installed
Best for: Larger households, homes with pools or ducted air conditioning, EV owners

A 10kW system moves you into serious energy production. With single-phase power (most Melbourne homes), you’ll typically pair this with a 5kW export-limited inverter or two inverters. The export limitation means some solar energy may be curtailed during peak production - but adding a battery or EV charger to use that excess energy locally resolves this entirely.

This size is particularly well-suited to homes that run energy-hungry appliances during the day (pool pumps, ducted heating/cooling) or charge an electric vehicle from solar.

13kW+ System

Daily production (Melbourne average): 43-55 kWh
Annual production: 15,700-20,000 kWh
Number of panels: 30-34
Roof space needed: Approximately 52-60 m²
Cost range: $11,000-$18,000 installed
Best for: Large all-electric homes, dual EV households, those pursuing energy independence

Systems above 13kW are increasingly popular as households electrify everything - replacing gas heating with heat pumps, adding EVs, and installing batteries. These larger systems often require three-phase power or careful export management.

With a large solar system, a battery, and smart EV charging, you can build a complete home energy solution that covers 80-95% of your total energy needs, including transport.

How to Choose the Right Size

Step 1: Understand Your Energy Usage

Check your electricity bill for your daily average consumption (measured in kWh). The average Melbourne household uses 15-20 kWh per day, but this varies enormously. A small apartment might use 8 kWh; a large family home with a pool and ducted air conditioning might use 40+ kWh.

Step 2: Factor In Future Changes

Are you planning to buy an EV? (Add 8-15 kWh/day for charging.) Replacing gas heating with a heat pump? (Add 5-10 kWh/day in winter.) Adding a home battery? (You’ll want surplus solar to charge it.) Building a home office? It’s almost always cheaper to install a slightly larger system now than to add panels later.

Step 3: Check Your Roof

Available roof space, orientation, and shading determine the maximum system size. North-facing roof space is ideal, but east and west-facing panels still produce well (roughly 85% of north-facing output). South-facing panels are generally not worthwhile in Melbourne.

Step 4: Consider Your Budget vs Returns

Larger systems have a lower cost per watt, but the return on investment depends on how much of the solar energy you actually use (self-consumption) versus export to the grid at a low feed-in tariff. The goal is to match your system size to your actual usage patterns.

Solar System Size and Battery Pairing

If you’re considering a battery (now or in the future), your solar system needs to produce enough surplus energy to charge it. As a rough guide:

• 6.6kW solar + 10 kWh battery: Good match for average households
• 10kW solar + 13.5 kWh battery: Good match for larger homes or EV owners
• 13kW+ solar + 20+ kWh battery: For maximum energy independence

For battery options and pricing, see our battery comparison guide and Victorian battery rebate information.

Get a Personalised Solar System Recommendation

The “right” solar system size depends on your specific household - energy usage, roof layout, budget, and future plans. Carlin Co provides obligation-free assessments that analyse your actual energy data and design a system that delivers the best return for your situation.

Call us on 0432 632 346 for expert advice on the right solar system size for your Melbourne home.