How to Choose a Solar Battery: A Simple Buyer’s Guide

Knowing how to choose a solar battery comes down to five things: how much stored power you actually use at night, whether it bolts onto your existing solar or replaces the inverter, the warranty behind it, the brand and its support, and how well it all works together. Get those right and a battery pays you back every single night. Get them wrong and you either run out of stored power by 9pm or pay for capacity you never touch. This guide walks you through each decision in plain English so you buy once and buy right.

What actually matters when choosing a solar battery?

Ignore the marketing spec sheets for a minute. Nearly every good buying decision comes back to a short list of things that genuinely change your day-to-day result.

• Usable capacity: how many kilowatt-hours you can really draw, not the headline number.
• Coupling: whether it is AC-coupled (bolts onto almost any solar) or DC-coupled (works through a hybrid inverter).
• Warranty: how many years, how much capacity is guaranteed at the end, and how much energy you can push through it.
• Brand and support: a reliable app, local backup and parts you can actually get.
• Compatibility: whether the battery plays nicely with your existing solar and inverter.

A battery you never fully use is money left on the table. A battery too small for your night-time habits leaves you buying power at the worst time of day. Sizing sits at the centre of the decision.

How much battery capacity do you actually need?

The right size is driven by how much electricity you use after the sun goes down, not by the size of your roof. Think about the evening: cooking, heating or cooling, hot water, TVs, and anyone charging an EV overnight. That overnight load is roughly the amount of electricity you want to cover on a normal day.

Three inputs set the number: your overnight usage, how much spare solar you generate during the day to fill the battery, and your budget. If you export a lot of cheap solar every afternoon, a bigger battery captures more of it for the evening. If your daytime solar is modest, a huge battery just sits half-empty. Most modern batteries are modular, so you can start with a sensible size and add more later as your usage grows or you add an EV.

For a deeper walkthrough on matching capacity to your home, read our solar battery buyer's guide.

AC-coupled or DC-coupled: which suits your home?

This is the decision most people have never heard of, and it quietly shapes the whole install. The short version: if you already have solar, AC-coupling is usually the easiest path. If you are starting fresh, DC-coupling is often the neatest.

AC-coupled (all-in-one) batteries

An AC-coupled battery has its own built-in inverter and connects to the AC side of your home. Because it converts power itself, it works alongside almost any existing solar system without ripping out what you have. That makes it the smart choice for most retrofits where the panels already work fine.

DC-coupled (hybrid) batteries

A DC-coupled battery connects to the DC side and runs through a hybrid inverter. Solar charges the battery directly with fewer conversion steps, which can be slightly more efficient. It tends to be the cleaner, tidier option when you are installing new solar and a battery at the same time, or replacing an ageing inverter anyway.

Rule of thumb: adding storage to solar you already own leans AC-coupled. Building a new solar-and-battery system from scratch leans DC-coupled.

What should you look for in the warranty?

A battery is a ten-year-plus purchase, so the warranty is where you separate a confident maker from a hopeful one. Read three lines before you sign anything.

• Length: how many years the battery is covered.
• End-of-warranty capacity: the percentage of storage the maker guarantees will remain at the end, since all batteries fade slowly with use.
• Throughput: how much total energy you can cycle through it over the warranty period.

Don't just take the biggest number. A battery you cycle every night should have a warranty that expects exactly that. A shorter warranty with poor capacity retention can cost you more over its life than a dearer battery that holds its charge and its cover.

Fox ESS, GoodWe or SolaX: how do the brands compare?

eHomes installs Fox ESS, GoodWe and SolaX batteries. All three are solid, widely-installed brands, and the best one is simply the one that fits your home, your existing gear and your budget. Here is a fair snapshot of where each tends to shine.

• Fox ESS: modular, high-voltage systems with a clean all-in-one design and flexible capacity you can stage over time. A practical, well-priced pick for many homes.
• GoodWe: a mature energy ecosystem with strong monitoring, a reliable app and broad integration across inverters, batteries and EV charging. A good fit if software and system integration matter to you.
• SolaX: modular and easy to expand in steps, so you can grow storage without a big upfront outlay. Works best paired with a SolaX hybrid inverter.

None of these is a one-size-fits-all winner. The right call depends on whether you are retrofitting or starting fresh, what inverter you already run, how much you value app features, and how you plan to grow your system. That is exactly what a proper site assessment is for. See our full solar battery range for more detail.

Does the battery need to match your inverter?

Compatibility can quietly rule options in or out, so it is worth checking early. Some batteries are happy alongside almost any inverter, while others are designed to run with a matching hybrid inverter from the same brand. If you are keeping your current inverter, an AC-coupled battery is usually the flexible choice. If you are replacing the inverter or going all-in on new gear, matching the battery and inverter can give you tighter control and simpler monitoring. A good installer checks this on day one, before anyone talks price.

What about rebates and finance?

Incentives and finance options change over time and vary by state, so it is easy to be caught out by information that is a year out of date. Rather than chase figures that shift, we keep a current summary on one page. See rebates and finance for what applies today, and we will factor anything you qualify for into your quote. If you are in South Australia, our Adelaide team can talk you through the local picture.

Storing your daytime solar to use at night is usually worth more than exporting it, which is why a well-sized battery makes sense for so many homes. The trick is matching the hardware to your habits, and that is where a tailored assessment beats any online calculator.

Frequently asked questions

What size solar battery do I need?

Size it to your overnight electricity use, not your roof size. Add up what you run in the evening and through the night, then match the battery's usable capacity to that, allowing for how much spare solar you generate to recharge it each day. Most batteries are modular, so you can start sensibly and expand later.

What is the difference between an AC-coupled and DC-coupled battery?

An AC-coupled battery has its own built-in inverter and bolts onto almost any existing solar system, which makes it ideal for retrofits. A DC-coupled battery runs through a hybrid inverter and charges more directly from your panels, which suits a brand-new solar-and-battery install. Which is better depends on whether you already have solar.

Which is the best solar battery brand?

There is no single best brand for every home. Fox ESS, GoodWe and SolaX are all reliable, widely-installed choices, and the right one depends on your existing inverter, whether you are retrofitting or starting fresh, your budget and the features you value. A site assessment is the quickest way to match a brand to your situation.

What should I check in a solar battery warranty?

Look at three things: how many years it is covered, how much storage capacity is guaranteed to remain at the end of that period, and how much total energy you can cycle through it. A battery you use every night should have a warranty that expects daily use and still holds a strong capacity figure at the end.

Can I add a battery to my existing solar system?

In most cases yes. An AC-coupled battery is designed to work alongside solar you already own without replacing your panels, and often without changing your inverter. The best way to confirm is a quick check of your current system, which we do as part of a free assessment.