What Size Battery Do I Need?

Start with how you use energy

The single most important factor is your evening and overnight energy use, because that's what the battery is there to cover. A household that's out all day and comes home to run aircon, cooking and entertainment in the evening has very different needs to one where someone's home runs appliances from morning onwards.

The goal is to store enough daytime solar to carry you through the expensive evening peak and into the night, so you're buying as little grid power as possible when it's dearest. To size that properly, we look at your actual consumption data, not an estimate.

Match the battery to your solar

There's no point having a big battery you can't fill. Your battery needs to be balanced against how much surplus solar you generate. If your panels produce plenty of excess during the day, a larger battery can capture it. If your solar is modest, an oversized battery will sit half-empty: money spent on capacity you never use.

Your inverter matters here too, as it sets limits on how the system charges and discharges. Sizing the battery, solar and inverter together as one system is the only way to get it right.

Think about the future, not just today

A battery is a long-term investment, so it pays to size with tomorrow in mind:

• EV on the horizon? An electric vehicle dramatically increases your energy needs. Sizing with that in mind now saves a costly upgrade later.
• Growing household? More people means more energy use.
• Battery degradation. Batteries gradually lose capacity over time, typically holding around 70% of their original capacity after about ten years. Sizing with headroom means your system still performs well down the track.

Why we often suggest a little extra

Where it makes sense, we tend to recommend sizing with some spare capacity. It builds in room for the future, it offsets that natural degradation, and it gives you surplus energy that can be exported. For customers who add our optional Power Trader system, that spare capacity can also be sold during high-value windows to earn more, though the future-proofing benefit stands on its own regardless.

Bigger isn't automatically better

Just as an undersized battery leaves value on the table, an oversized one means paying for capacity you can't use. The right size is the one that fits your usage, solar and goals, which is why we don't sell one-size-fits-all packages. Proper sizing is design work, and it's where a lot of a system's value is won or lost.

The bottom line

There's no universal "right" battery size, only the right size for your home. It comes down to your evening usage, your solar generation, your inverter and your future plans. Get those right, and your battery earns its keep for years.