Summary
- Partial battery backup (~70%) is the smartest bang-for-buck setup
- Always design for your worst months, not your best
- 7.1kW of panels is the sweet spot for a 17kWh/day house in rough winters
- Bigger arrays = cheaper energy, better reliability, easier upgrades
How we balance solar panels and battery storage in an off-grid system
Thinking about ditching the power companies for good?
Going off-grid with solar is a brilliant move — but only if you set it up smart.
The best way these days? Partial battery backup.
Saves you a bucketload of cash, keeps you running almost all the time, and leaves room to grow later if you need.
Let’s run through how it works — and why it’s the smart move for Aussies everywhere.
Why Partial Battery Backup Works Better
You don’t need a battery to cover 100% of your usage.
Most folks do way better with a battery that handles around 70% of their daily needs.
Why?
Because:
- You don’t blow your budget on a massive battery bank
- You’re not paying for storage you hardly ever use
- You can add more later if you really need it
- Solar keeps daytime stuff running without hammering the battery
It’s the new common-sense approach.
Especially good if you’re in places with heaps of sunshine most of the year.
Want to see what batteries suit you best? Check out our battery systems.
Real Test Case: Ballarat’s Rough Winters
Ballarat’s a tough gig for solar in winter.
Short days, cold mornings, endless clouds.
If you can make a system work there, it’ll work anywhere.
Here’s what a 1kW system pulls in Ballarat:
| Month | Average Solar Radiation (kWh/m²/day) | Monthly AC Output (kWh) |
|---|---|---|
| May | 3.25 | 82 |
| June | 2.90 | 72 |
| July | 2.87 | 74 |
Solar data from https://pvwatts.nlr.gov/
In June, you’re getting around 2.4kWh per day off 1kW of panels.
Not a lot — but still enough if you design it right.
Want to see real-world setups? See our off-grid systems installed across Australia
How Much Solar Do You Really Need?
Say your place actually pulls about 17kWh a day, pretty typical for a 2 bedroom, 3 person family home.
If your battery’s covering 70% (around 12kWh), then your solar needs to:
- Charge the battery
- Run your daily loads (like lights, TV, fridge, etc.)
End of the day, you’re chasing about 17kWh from solar each day.
In a Ballarat winter, that means installing roughly:
| Solar Size | Winter Daily Output |
|---|---|
| 7.1kW | ~17kWh |
So even in rough old June, a 7.1kW system paired with a 12kWh battery gets you through.
Keen to see what complete solar kit performs best for your usage? Calculate your usage and find your off grid kit
How we size solar panels and batteries to work together
More panels today means less headaches tomorrow. That’s true whether you’re in Ballarat, Byron, or out the back of Bourke.
- Panels are way cheaper than batteries
- More panels = bigger rebates from the government
- It’s dead easy to add a battery later — adding panels after? Not so much.
- Bigger arrays mean faster charging even on miserable grey days
If you’ve got the roof space, fill it. Simple as that. – Fred
Keen to see what solar setup suits your property best? See our solar system range.
