Getting solar quotes and feeling a bit overwhelmed by all the different system sizes? You're not alone. With 6kW, 6.6kW, 10kW systems and everything in between, it can be tricky to know what's right for your specific situation.
The truth is, there's no one-size-fits-all answer. Your ideal solar panel system size depends on your household's energy usage, when you use that energy, your roof space, and your future plans. Some homes do brilliantly with larger systems, while others get better value from something smaller and more targeted.
Let's break down how to work out what size solar system actually makes sense for your home, your usage patterns, and your budget.
The golden rule: match your system to your daytime usage
Here's what most people don't realise - with feed-in tariffs significantly lower than what you pay to buy electricity from traditional retailers, selling power back to the grid isn't the money-maker it used to be.
The sweet spot? A system that generates roughly what you use during the day - or what you expect to use in coming years (perhaps you’re planning on getting an EV, for example). This way, you're using your own solar power instead of paying for power from the grid, and you're not stuck selling excess power back for peanuts.
Know your usage pattern
Before you even think about system size, you need to understand when you use power. Most Aussie households have what's called a "morning and evening peak" pattern - big spikes when everyone's getting ready for work or settling in for the night, with a dip during the day when the house is empty.
If that sounds like you, a 6kW system typically works well for a household using around 20kWh per day. But here's where it gets interesting...
The game-changer: shifting your usage
Remember those old-school timers your parents used for the hot water system? Time to bring them back! By shifting major energy draws like hot water heating, pool pumps, dishwashers, and washing machines to run during the day, you can dramatically improve your solar payback. The same system that might only offset a portion of your usage with evening-heavy consumption could suddenly cover much more when you shift loads to daytime - so you can use your own power.
That difference can add up to hundreds of dollars per year in extra savings!
What size actually makes sense?
Based on current pricing and feed-in rates, here's what we're seeing across different scenarios:
For typical morning/evening peak households:
- 6kW systems consistently offer the best payback period (check out our ROI calculator here)
- Going bigger to 10kW might give you more total savings, but your payback stretches to 5+ years (with the caveat that you may be planning on electrification/getting an EV)
- Smaller systems (3-4kW) cost more per kW installed, so unless roof space is really tight, they're rarely the best choice
For households that can shift usage to daytime:
- 6kW still hits the sweet spot for payback
- You get better total savings across all system sizes
- The financial benefit of going larger is still marginal
Planning for the future
Now, this is where strategy comes in. Expanding your solar system later is possible but expensive - you're essentially paying for installation twice. So if any of these are on your radar, consider sizing up now:
- Installing aircon (especially ducted)
- Adding a granny flat
- Going electric with cooking, hot water, or heating
- Getting an electric vehicle
- Installing a pool
- Working from home more
An extra kW or two upfront costs much less than a system expansion down the track.
What about batteries?
Batteries are becoming an increasingly popular part of Australian solar setups, and for good reason. While the upfront investment is significant, they can deliver real value in the right circumstances.
Here's where batteries really shine:
- Peak avoidance: If you're on time-of-use tariffs, a battery can help you avoid those expensive evening peak rates by storing your daytime solar for use later
- Backup power: Keep essential loads like fridges, lights, and security systems running during outages
- Energy independence: Reduce your reliance on the grid and take control of your energy costs
- Future-proofing: As electricity prices continue to rise, having your own stored energy becomes more valuable
The key is sizing your solar system to work with your battery. You'll want to generate enough excess during the day to meet your daytime needs and charge your battery up with enough excess energy to cover your evening’s requirements and have some extra leftover to sell back to the grid. This often means going a bit larger on the solar side to maximise the benefits of your battery investment.
Real talk: when bigger isn't an option
Sometimes the "optimal" system size just isn't possible. Your roof might not have enough unshaded north-facing space. Your local network might have restrictions on system size. Or your budget might cap what you can spend upfront.
That's totally fine - a slightly smaller system that you can actually afford is infinitely better than the "perfect" system you can't buy. Plus if you do get a battery down the track, charging it up on cheap renewable energy from the grid during the day can more than compensate for a smaller solar system.
So what's the answer?
Look, for most Aussie homes, you'll probably land somewhere around 6-6.6kW. It's the sweet spot where you're not overpaying per kW, but you're not generating so much excess that you're basically donating power to your retailer.
But here's what really matters - don't let a sales rep talk you into something that doesn't fit your actual situation. The "perfect" system on paper means nothing if it doesn't match how you actually live and use power. Keep in mind though that your present situation may not be the same in 5 years.
Getting started
Want to crunch the numbers for your specific situation? Start by:
- Reviewing your last 12 months of electricity bills to understand your usage patterns
- Thinking about major energy changes you might make in the next 5-10 years
- Getting quotes from multiple installers for different system sizes
- Using online calculators (like our ROI calculator!) to model payback periods based on your actual electricity rates
And remember - the best solar system is the one that fits your roof, your budget, and your lifestyle.
Ready to get solar quotes tailored to your actual needs? At Amber, we help Australians make smarter energy choices. Our platform connects you with quality local installers who focus on what works for you, not what maximizes their profit. Contact us today to find out more.
