How Big Should Your Solar Battery and System Be?

Imagine this: it’s a chilly winter evening. The power goes out just as you’ve sat down to dinner. The neighbours’ houses go dark, but your lights stay on. The Wi-Fi hums, the heater keeps running, and the fridge doesn’t skip a beat. That’s the comfort of a well-sized solar battery. It doesn’t just store energy, it keeps your household ticking along when the grid can’t.

But here’s the tricky part: not all batteries are created equal, and not all homes need the same thing. Get the size wrong, and you could end up with a battery that’s rarely full, or one that runs flat before the night is over. Or, maybe your battery won’t power your home properly in the black out at all! So, how do you find that “just right” fit? Let’s explore.

Your Solar System Feeds Your Battery

Think of your solar panels as a tap and your battery as a water tank. If the tap only trickles while you keep using the tank water like normal, you may never fill the tank.

That’s why, for most Shoalhaven homes, we recommend around 10 kW of solar panels if you’re investing in a sizeable battery. Smaller systems (like 6.6 kW) often struggle in winter, meaning your battery may not fully charge when you need it most.

kW vs kWh – Cutting Through the Jargon

Let’s keep it simple:

• kW (kilowatts) – how much power your system can produce at a given moment.

• kWh (kilowatt-hours) – how much energy you’ve stored or used over time.

Example: a 10 kW solar system running at full tilt for one hour produces 10 kWh, which is enough to half-fill a 20 kWh battery.

What Does a Home Actually Use?

• Winter: 20–30 kWh for an average home; 30–40 kWh for larger homes with heating.

• Summer: 15–20 kWh for smaller homes; 25–35 kWh for bigger homes.

Heating usually uses far more energy than cooling, which surprises many people.

Backup Power: Some or All?

• Partial backup: keeps essentials like lights, Wi-Fi and maybe one fridge going if it’s on the right circuit.

• Whole home backup: powers everything, from your kettle to the air con.

If you’re in Berry Mountain or Kangaroo Valley or Bundanoon, where outages are not uncommon, whole home backup is worth it. In Nowra, Bowral or coastal suburbs with fewer blackouts, a partial backup system may be all you need.

How Long Will It Last?

• 16 kWh battery: around 8 hours of essential use.

• 24 kWh battery: longer, but still depends on what you’re running.

Heavy loads (like cooktops, heaters, or pool pumps) will chew through stored power quickly.

Smarter Tools for Smarter Homes

Modern batteries, like the Sigenergy SigenStor, come with monitoring that shows you exactly what each appliance uses. It’s eye-opening to see just how quickly a dishwasher or heater can drain a battery, and empowering, too. With this knowledge, households can make smarter choices to stretch their stored energy further.

The Shoalhaven Solar Difference

We don’t just install batteries. We design systems that suit your home and lifestyle. From reviewing your power bill to matching you with the right solar size and backup plan, we’ll make sure your investment delivers.

📞 Call us today on (02) 4464 1597 to find your perfect battery fit.