The Question Nobody Asks Before Selling You A Battery

Last week I was in Officeworks waiting for some printing. Next to me, a woman was buying a laptop, and the Officeworks bloke helping her knew his stuff. Processors, RAM, screen brightness: all of it correct. Then he asked whether she’d considered a Mac, which opened a second long conversation about MacBooks, and by the end of it, she looked more confused than when she started.

He left her to think it over. I couldn’t help myself.

“Excuse me. What kind of phone do you have?”

She gave me the look you’d expect from a stranger in Officeworks. Then: an iPhone. And an iPad she uses all the time.

In that case, I said, the Mac is a no-brainer. Your photos, messages, passwords and files will just turn up on it. That will matter more every single day than which chip is inside or how many nits the screen pushes out.

I don’t know what she bought. But I walked out thinking about how often I watch the same conversation happen with home batteries, and how rarely anyone asks the equivalent question.

Nobody asks what you already own

Post “which battery should I get?” in any Australian solar Facebook group and you’ll have thirty replies within the hour. Most will name the brand the replier bought. A few will argue about dollars per kWh. Someone will bring up cycle life. Almost nobody will ask what’s on your roof, what inverter it’s plugged into, whether there’s an EV in the driveway or what appliances you need to power, and which of those need backup.

Many professional salespeople aren’t much better. Plenty of the quotes I see are a battery bolted onto whatever was already there, powering mystery loads. The battery model chosen because it’s what the installer likes to install.

Where possible, buy the same brand inverter, battery and EV charger.

What matters is whether the battery can play nice with the existing solar inverter, how much solar you’ve got, and what loads you need to power.

If you get three boxes from three companies, each optimising its own corner, it’s a mess. The EV charger doesn’t know the battery is nearly flat. The battery doesn’t know the 7kW load it’s just seen is an EV that should be left to charge from a cheap grid tariff. You get three apps and about a million CTs in your switchboard, all measuring the same current, all points of failure.

Sungrow inverter, Sungrow battery, Sungrow EV charger. Fronius hybrid inverter with a Fronius or BYD battery and Fronius Wattpilot EV charger. Sigenergy stack with Sigenergy AC EV charger. Enphase? If you can wait till 2027, their new battery and EV chargers look like they’ll finally be worth buying.

How much solar you own matters too

“What do you already own?” also tells you whether you need more solar. A 6.6 kW system from 2016 will not fill a 20 kWh battery in June in Adelaide, never mind charge an EV on top. Sometimes the right answer to “which battery” is “more panels first”.

What solar you own also tells you whether to AC or DC couple. A top-quality inverter with years of warranty left points to AC coupling: leave it alone and add a battery beside it. An old string inverter from a brand that has abandoned the lucky country points to DC coupling with its own solar inverter.

Careful, some ecosystems die

I started with an Apple analogy. That has a limit.

Apple will still be around when that lady’s MacBook, iPhone and iPad get recycled. Inverter brands have a worse record. I’ve watched dozens go broke or leave Australia since I started SolarQuotes, and when a brand goes, its app, its cloud, its firmware updates and its warranty all go together. Putting your inverter, battery and charger with one company only pays off if that company stays alive and kicking in Australia.

So buy one ecosystem, and make it a brand with the balance sheet to still be here in 2036. That narrows the field to the big names, and I’m fine with that.

How to filter installers

If you’re buying, choose an installer who asks what’s on your roof, which inverter it’s connected to, what car is in the driveway or on order, and what loads you want to power – under normal circumstances and during a blackout.

If nobody’s asked you yet, you haven’t met a good installer.