If you’re looking at solar in Ballarat, you’ve probably already guessed – winter is a different game compared to summer.
Short days, cloudy skies, and colder temps can really knock solar production around.

That’s why it’s important to size your system based on the worst months, not the best ones.

How Much Solar You Get in Winter

Here’s the real story from actual Ballarat data for a 1kW system:

Month	Average Solar Radiation (kWh/m²/day)	Monthly AC Energy (kWh)
May	3.25	82
June	2.90	72
July	2.87	74

In June, you’re looking at about half the output you’d get in January.
So if you want your system to perform all year round, you have to plan for the worst, not the best.

What 1kW of Solar Really Does in June

We ran the numbers across every day of June.
This is what a 1kW system gave:

Best day: 3.87 kWh
Worst day: 0.20 kWh
Average day: around 2.4 kWh

So yeah, it’s patchy — sunny days are great, cloudy ones… not so much.

(Insert graph here when you post this.)

How Big Should Your Solar System Be?

Let’s say your home uses about 17kWh a day (pretty typical for Ballarat).

Here’s what you’d need:

System Size (kW)	Average Daily Solar Output (kWh)	Shortfall or Surplus
6kW	14.4 kWh	–2.6 kWh shortfall
7kW	16.8 kWh	–0.2 kWh (almost spot on)
8kW	19.2 kWh	+2.2 kWh surplus

✅ A 7kW system gets you nearly there.
✅ An 8kW system gives you breathing room for cloudy spells.

What About Batteries?

If you want real independence (even when it rains for days), you’ll need batteries too.

For a full backup, you’d want around 25.5kWh of usable battery.
That covers at least 1.5 days of power if the sun completely disappears.

Good options would be two BYD stacks, a Tesla Powerwall 3, or similar.

Another Way: Partial Battery Backup

You don’t have to cover 100% with batteries.
A lot of people size their batteries to cover about 70% of daily needs. Cheaper and still super practical.

If you do that:

Battery size needed: around 12kWh usable
Solar still needs to charge that battery and power the house during the day.

So guess what?
You still need a 7.1kW solar system to safely get through winter.

Why It’s Smarter to Go Bigger on Solar

Here’s the thing:

Solar panels are cheaper than batteries.
Panels attract government rebates (more panels = bigger rebate).
It’s easy to add a battery later, but adding more panels is a real headache — council approvals, scaffoldings, wiring upgrades… expensive stuff.

That’s why it makes way more sense to max out your roof now.
Bigger array = smaller battery needed later.
And you’ll future-proof yourself if your energy needs go up.

Quick Recap

You need at least 7.1kW of solar to cover a 17kWh/day house in winter.
8–9kW is even better, giving a buffer for cloudy weeks.
25.5kWh battery = full backup, but 12kWh battery works too if you only want partial coverage.
Oversize the panels now — it’s cheaper, easier, and smarter long term.

Need help designing the right system for Ballarat’s real winters?
Chat with Re-Energy — we design smart, practical solar and battery setups that work, rain or shine.

Solar data from https://pvwatts.nrel.gov/index.php