When comparing home batteries, most homeowners understandably start with two numbers:
How many kilowatt-hours does it store? and How much does it cost?
Both matter. But they don’t tell the whole story.
If you’re comparing two or three battery systems, here are eight other things worth understanding before making your decision.
1. Usable battery capacity
Battery capacity is measured in kilowatt-hours – kWh.
But make sure you’re comparing usable capacity, rather than simply the total or nominal amount of energy contained inside the battery.
Usable capacity tells you how much energy the battery is actually designed to make available to your home.
This is the figure that matters when determining how long the battery may support your household.
2. Battery power
Capacity and power are not the same thing.
Think of capacity as the size of the fuel tank. Power is how quickly energy can come out of it. A large battery with relatively low output power may store plenty of energy but still be limited in how many high-powered appliances it can supply simultaneously.
This becomes particularly important if you want to run loads such as:
- large air conditioners;
- induction cooking;
- electric hot water;
- pool equipment;
- pumps; or
- other high-demand appliances.
Power capability also matters when designing backup systems.
3. Can the battery grow with you?
Household electricity use is changing rapidly.
A home that requires 15 kWh of storage today may require substantially more in five years after adding an EV, heat-pump hot water or replacing gas appliances.
Modular battery platforms can provide useful flexibility.
Sigenergy uses modular battery packs within its SigenStor architecture, Sungrow uses modular battery systems, Fronius Reserva also uses a modular architecture, while Tesla Powerwall 3 can be expanded using additional expansion units.
The important question is not simply: “Can I add more battery?”
It is: “How easily and in what increments can I add it?”
4. Single-phase or three-phase?
This is an area where professional system design matters.
Australian homes can have either single-phase or three-phase electrical supplies.
Different battery and inverter systems handle these configurations differently.
Sigenergy and Sungrow offer both single-phase and three-phase hybrid inverter platforms. Fronius provides compatible single- and three-phase hybrid inverter options depending on the configuration. Tesla’s Australian Powerwall 3 itself is specified as a single-phase system.
That doesn’t mean one is automatically better than another.
It means the electrical design of your property needs to be understood before choosing the equipment.
5. What happens during a blackout?
Not every battery installation automatically means your entire house will operate normally during a blackout.
Backup design can vary significantly.
You need to consider:
- whether backup is included;
- which circuits will be backed up;
- maximum backup power;
- whether large appliances can operate;
- how quickly backup engages; and
- how long the battery capacity is likely to last.
A household wanting basic backup for lights, refrigeration and internet has very different requirements from a household wanting to maintain air conditioning, cooking and other significant loads.
Define your backup objective before choosing the battery.
6. How good is the software?
You may interact with the battery’s app far more often than you interact with the battery itself.
Good monitoring should make it easy to understand:
Solar -> Home -> Battery -> Grid
You should be able to see where your energy is coming from and where it is going.
More sophisticated systems may also provide different energy strategies, electricity-tariff optimisation and other automated functions.
Tesla, Sigenergy, Fronius and Sungrow each provide their own energy-monitoring ecosystem.
Don’t underestimate this part of the buying decision.
7. How strong is the warranty and manufacturer?
Most major premium residential batteries now offer long product warranties, frequently around 10 years.
But don’t compare warranties based on the headline number alone.
Read what happens to warranted battery capacity over time and whether there are throughput or operating conditions attached.
Also consider the manufacturer itself.
Will spare parts be available?
Is there Australian technical support?
Does the manufacturer have an established energy business?
Does it continue to support older products?
Nobody can guarantee exactly what will happen to any company over the next decade.
But when buying equipment intended to remain on your home for many years, manufacturer quality and support deserve consideration.
8. Who is installing and supporting it?
This may be the most overlooked consideration of all.
The best battery in the world can still perform poorly if the system is badly designed or installed.
And even high-quality equipment can occasionally experience faults.
When that happens, you want an installer who understands the product and is prepared to help.
Ask:
- Does the installer regularly install this battery?
- Do they have trained in-house technicians?
- Can they diagnose problems after installation?
- Do they have a service department?
- Will they manage manufacturer warranty issues?
At AG Solar, our installation and service capability is part of the reason we intentionally limit the number of major battery platforms we support.
We would rather know a smaller number of systems well than sell whatever product happens to be cheapest at the time
Don't choose a battery from a specification sheet alone
Specifications are useful. But a battery isn’t being installed in a laboratory. It’s being installed in your home.
The right system depends on your property, roof, switchboard, solar system, phase configuration, electricity consumption, tariff and future plans.
That’s why we recommend starting with the household rather than starting with the battery brand.
At AG Solar, we work primarily with Tesla, Sigenergy, Fronius and Sungrow and can explain where each platform performs particularly well.
Based in Caringbah, AG Solar has extensive experience designing, installing and supporting solar and home battery systems throughout the Sutherland Shire, Southern Sydney, Wollongong and the Illawarra.
Sometimes the answer is obvious.
Sometimes two products are both excellent choices and the decision comes down to personal priorities.
Either way, a good solar consultant should be able to explain why they’re recommending one system over another.
If you’re comparing home batteries and want help making sense of the differences, speak with the AG Solar team.
We’ll help you compare the things that actually matter.
