Quick Summary
For many Australian homeowners researching solar, the 6.6 kW system is often the first option they encounter. It has long been marketed as the “standard” residential system size. However, the Australian solar market has changed significantly over the past few years.
Today, more households are choosing larger systems, with installations around 13 kW becoming increasingly common. Rising electricity usage, declining feed-in tariffs, and future electrification are changing how solar systems are designed.
The most important question is no longer which system is cheapest upfront. The real question is which system delivers better value over the next 20 to 30 years.
This guide explains the true cost difference between a 6.6 kW and 13 kW solar system and why many homeowners now choose to install larger systems from the beginning.
Why 6.6 kW Became the Default System Size
The 6.6 kW system became popular years ago because it matched older inverter export limits and suited households with lower electricity consumption.
At the time:
- Electricity usage was lower
- Batteries were uncommon
- Electric vehicles were rare
- Feed-in tariffs were higher
A smaller system could still deliver strong financial returns.
Today, household energy use looks very different.
Air conditioning, home offices, electric hot water systems, and EV charging have increased electricity demand dramatically. Many homes now consume far more energy than a 6.6 kW system can offset.
How Much More Does a 13 kW System Actually Cost?
One of the biggest misconceptions is that doubling system size doubles the price. In reality, the cost increase is much smaller.
Many installation costs remain the same regardless of system size, including:
- Site inspection and design
- Electrical labour setup
- Compliance testing
- Travel and installation logistics
- Grid connection processes
Because these fixed costs already exist, adding additional panels increases production far more than it increases total price.
In many cases, upgrading from a 6.6 kW system to a 13 kW system represents a moderate upfront increase while delivering substantially higher lifetime energy generation.
Energy Production Difference Over Time
The biggest financial advantage of a larger system is energy output.
A 13 kW system can produce roughly double the electricity of a 6.6 kW system under similar conditions. Over a 25 year lifespan, that difference becomes enormous.
More generation means:
- Greater reduction in grid electricity purchases
- Better protection against rising tariffs
- More flexibility for future energy use
- Higher long term savings
Electricity prices historically trend upward over time. Every additional kilowatt hour generated by your system becomes more valuable as grid prices increase.
Why Electricity Usage Is Rising in Australian Homes
Modern homes are electrifying rapidly.
Common drivers include:
- Reverse cycle air conditioning
- Electric cooking
- Heat pump hot water systems
- Electric vehicles
- Work from home energy demand
Many households installing solar today are planning for energy needs they do not yet have. A system sized only for current usage can quickly become undersized within a few years.
This is one of the main reasons behind the national shift explained in our guide on why Australians are choosing bigger solar systems.
The Hidden Cost of Installing Too Small
Choosing a smaller system can appear financially safe at first, but it often creates long term limitations.
Undersized systems may:
- Leave high evening electricity bills unchanged
- Limit future battery performance
- Require costly upgrades later
- Deliver slower long term savings growth
Upgrading later is rarely simple. Additional installation work, inverter changes, and compliance updates often make expansions more expensive than installing the correct size initially.
Feed-In Tariffs Have Changed the Equation
In earlier years, exporting excess solar energy generated meaningful income. Today, feed-in tariffs are significantly lower across most states.
The value of solar now comes primarily from using your own electricity rather than exporting it.
A larger system increases the amount of energy available for self-consumption and future battery storage, improving overall financial performance.
Planning for Future Energy Needs
Many homeowners now install solar with future upgrades in mind, including:
- Battery storage
- Electric vehicle charging
- Full home electrification
- Increased cooling demand
If you plan to add storage later, understanding how solar system size changes when adding a battery becomes critical, as battery performance depends heavily on available solar generation.
Long Term Value vs Upfront Price
Solar systems typically operate for decades. When evaluated over their lifespan, the difference between system sizes becomes a long term investment decision rather than a short term purchase.
A larger system can:
- Generate significantly more lifetime energy
- Reduce reliance on rising electricity prices
- Provide flexibility for future technology adoption
- Improve return on investment over time
The upfront price difference often becomes small compared to decades of additional energy production.
Choosing the Right System Size
Every home is different. Roof layout, electricity usage, and future plans all influence optimal sizing.
Rather than choosing a system based purely on advertised packages, homeowners benefit from systems designed around real household energy behaviour.
You can use our free solar calculator to estimate the right system size based on your usage and future energy plans.
Final Thoughts
The shift from 6.6 kW systems toward 13 kW installations reflects a smarter approach to energy planning.
As electricity usage grows and feed-in tariffs decline, larger solar systems increasingly provide stronger long term value. For many households, the question is no longer whether to install solar, but whether installing a smaller system today will limit savings tomorrow.
Contact Stag today for expert solar advice!
Frequantly Asked Questions
