With the federal battery rebate kicking in from July 1, demand for home battery quotes has gone ballistic.
It’s not hard to see why. Thousands of dollars in subsidies. Rising grid prices. More households with solar. And batteries finally starting to feel like part of the modern home, not a science experiment bolted to the garage wall.
So the question flying in thick and fast is:
“What size battery should I buy?”
But I reckon that’s the second question you should be asking.
The first is this:
“Do I want a battery that makes financial sense, or one that makes me happy?”
Because the battery that gives you the best financial return is likely smaller than you expect. For fastest payback, you want it to fully discharge most nights, so you’re wringing every drop of value from those lithium cells. For many homes, that’s a battery as small as 5 kWh. In fact, some well-meaning government departments have even recommended a teeny tiny 5 kWh battery as optimal for most homes.
But there’s a catch.
It is not hard to tell which house on the street is mine when there’s a blackout.
Blackouts & Battery Degradation
Go too small and you’ll regret it. Not in your payback spreadsheet, but in real life.
You’ll be the one in a blackout with no reserve and no lights (if you are worried about blackouts, you should reserve at least 2 kWh for backup duties).
You’ll be the one kicking yourself when winter nights demand a top-up from the grid during the peak pricing period.
And don’t forget: batteries degrade. Most are only warranted to retain 70% of their original capacity after 10 years. So that “just enough” 5 kWh battery could shrink to 3.5 kWh by the time it hits double digits. Still technically working, but barely. You’ll spend more time topping it up and less time feeling like it’s pulling its weight. At that point, you’ll ask yourself: why did I even bother?
A Different Kind Of Rational
Which is why, if you can afford it, adding a few extra kilowatt-hours now makes more sense than ever. With the new rebate, those extra kWh come at a serious discount. What felt like a splurge a few weeks ago might now be the smarter, longer-term move.
It’s not irrational. It’s just a different kind of rational.
So go ahead, crunch the numbers. But before you do, be honest about what’s more important to you, the shortest payback period, or the peace of mind that your battery’s actually got your back.