Got Solar? These 3 Numbers Tell You If You Need a Battery

By Spiring Energy

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Last Updated JUL 2. 2026

3 hours of free electricity every day — the real question is: can you make it work for your home?

The 30-Second Answer

If your feed-in tariff is below 8 cents per kWh and you're not home using power during the day, you're almost certainly better off with a battery.

 

Here is why.

 

Most Australian homes with solar are stuck in a lopsided trade. You sell your excess daytime power to the grid for 5 to 8 cents per kWh. Then at 6pm, when the sun is down and everyone is cooking dinner, you buy it back for 30 to 45 cents per kWh.

 

That is a 5x to 8x price gap. Every single day.

 

A 10 kWh battery can shift enough solar into the evening to cut that gap by 60 to 80 per cent. For the average Aussie household, that is $800 to $1,500 back in your pocket each year — on top of what your solar already saves you.

 

And with the federal Cheaper Home Batteries Program covering roughly 30 per cent of the upfront cost, the maths has never been stronger.

 

Not sure where you sit? Grab your last electricity bill. You are about to find out in 2 minutes.

Number 1 — Your Feed-In Tariff

This is the single number that decides whether solar alone still works for you.

How to Find It

Open your electricity bill. Look for a line that says "Feed-in tariff" or "Solar export rate." It will be a cents-per-kWh number.

 

If you cannot find it, log into your energy retailer's app or call them. The question takes 30 seconds: "What is my current solar feed-in tariff?"

What the Number Means

Your Feed-In Tariff What It Means for You
Above 12c/kWh You are on a valuable legacy tariff. A battery can still provide benefits, but upgrading is generally less urgent.
8c – 12c/kWh You are in the middle range. A battery is likely to become financially attractive within the next couple of years.
Below 8c/kWh Your excess solar exports are generating limited value. Battery storage can significantly improve your solar savings.
Below 5c/kWh (or $0) Some retailers now offer little or no payment for exported solar. Battery storage is often the fastest way to maximise the value of your solar system.

If your rate is under 8 cents, you are already in "battery territory." That number alone tells you the direction. The next two numbers tell you how much it is actually costing you.

 

On 1 July 2026, the federal battery rebate is scheduled to phase down further. Acting sooner locks in more value. Check your eligibility in under a minute.

Number 2 — Your Daytime Solar Surplus

Your solar panels generate power. Your home uses some of it. The rest — your surplus — gets exported to the grid for whatever your feed-in tariff pays.

 

The bigger your surplus, the more you are giving away.

Where to Find This Number

Most solar inverter apps (Fronius Solar.web, Sungrow iSolarCloud, Tesla, GoodWe SEMS) show a daily graph with two lines: generation and consumption. Look at a sunny weekday when nobody is home.

 

The gap between those two lines between 10am and 3pm? That is your surplus.

 

If you do not have monitoring, your bill may show "total exported" — divide by the number of days in the billing period. For a 6.6kW system, a surplus of 10 to 20 kWh per day is typical for a working household.

The Simple Maths

A typical Sydney household with a 6.6kW solar system exports about 15 kWh per day.

 

At a 6c feed-in tariff, that earns you: 90 cents.

 

Buying back just 5 kWh during the evening peak at 40c/kWh costs you: $2.00.

 

Net result: you lost $1.10 today, despite generating free power all afternoon.

 

Multiply that by 365 days. That is over $400 a year vanishing — and that is before we look at what you spend on evening electricity.

Number 3 — Your Evening Grid Spend

This is the number most people never check. It is also the number that makes a battery obviously worth it.

Where to Find It

Most energy bills now include a usage breakdown by time block. Look for "Peak" or "Shoulder" usage between 4pm and 9pm. If your retailer does not show this, check your inverter app for consumption after sunset.

 

Alternatively, take your total quarterly bill, subtract the daily supply charge (usually around $1.00 to $1.20 per day), and subtract whatever credits your solar export earned. What is left is what you are paying for grid power — and the bulk of that is happening in the evening.

A Real Example

A Melbourne family with a 6.6kW solar system tracked their evening usage for one month:

  • Evening grid consumption: 8 kWh per day
  • Average evening rate: 38c/kWh
  • Monthly evening cost: $91
  • Annual evening cost: $1,092

That same family, with a 13.3 kWh battery covering their evening hours, would slash that annual cost to roughly $200 to $300.

That is over $800 saved per year from evening usage alone — and that is before any VPP credits or monthly electricity credits.

 

Want to see your numbers? Explore how the Spiring Plan works — you may be surprised how quickly it adds up.

The 2-Minute Self-Test

Pull your three numbers together:

Battery Zone Checker

Enter your numbers below to see whether a home battery is likely worth it.

Metric Your Number Battery Zone Trigger Result
Feed-in Tariff Below 8c —
Daily Solar Surplus Above 8 kWh —
Evening Grid Spend Above $60 —

If your numbers are borderline, that is fine too. The Eco tier is built exactly for this — a 13.3 kWh battery with a 5 kW inverter, installed from $6,211 with the lock-in plan, designed for 1-3 person homes that want to stop giving away free power without overcommitting.

"OK — Which Battery Size for My Home?"

This is the most common question on Australian energy forums, and the answer is simpler than most guides make it sound:

Find Your Recommended Battery Plan

Enter your typical evening usage and daily solar surplus to see which Spiring plan is the best fit.

Your Evening Usage Your Solar Surplus Best Fit
5–8 kWh 8–12 kWh/day Eco — 13.3 kWh Battery
8–12 kWh 12–18 kWh/day Core — 26.6 kWh Battery
12–16 kWh 18–25 kWh/day Max — 27.9 kWh Battery
16+ kWh 25+ kWh/day Ultra — 37.2 kWh Battery

The Core tier is our most popular — it covers 2-4 person homes with average evening usage, bringing electricity bills down to around $90-$130 per month with up to $576 in annual electricity credits.

See which tier fits your home — you can check in under a minute, no commitment.

When the Numbers Say "Not Yet"

We believe in being upfront. A battery is not right for everyone, and here is when you should probably wait:

 

You still have a premium feed-in tariff. Some SA households are locked into 44c/kWh until 2028. If that is you, do not touch anything yet — adding a battery could void your legacy rate.

 

You are home all day using most of your solar already. If your self-consumption is already high (above 60 per cent), the additional savings from a battery shrink considerably.

 

You are planning to move within 3-4 years. The payback window for a battery is typically 5-7 years with current rebates. If you are selling sooner, the next owner will benefit more than you.

 

Your inverter is 10+ years old and incompatible. In this case, a full system refresh might make more sense than retrofitting. Our team can help you figure that out — get in touch with a recent bill and we will give you a straight answer.

 

Frequently Asked Questions

Almost always yes. The panels themselves are rarely the issue — it is your inverter that matters. If your inverter is less than 7–8 years old, it is likely compatible.

If it needs replacing, an AC-coupled battery (which has its own built-in inverter) is a straightforward retrofit. Learn more about how Spiring handles installation.

With the federal Cheaper Home Batteries Program active, a typical battery retrofit ranges from $6,000 to $12,000 depending on capacity and inverter compatibility.

Spiring Energy's managed plans start lower because we spread costs differently. The Eco tier starts from $6,211 including the battery, inverter and standard installation.

Check your eligibility to see what you qualify for.

Yes — but only if the system is configured for backup.

Not all battery systems include blackout protection by default, so it is worth confirming with your installer.

All Spiring Energy systems are configured with backup capability, helping keep essential appliances running when the grid goes down.

For most Australian households in 2026, the typical payback period is around 5–7 years with the federal rebate.

The return can improve if you are on a time-of-use tariff with high evening electricity prices, or if you participate in a Virtual Power Plant (VPP) program that earns additional credits.

Individual results vary based on electricity usage, solar production and retailer pricing.

The Bottom Line

Your solar panels are already doing half the job. They generate free power every day. But without a battery, you are selling that power cheap and buying it back expensive every single evening.

 

Those three numbers on your bill — feed-in tariff, surplus, and evening spend — tell you exactly how much that gap is costing you.

 

For most Australian homes in 2026, the answer is: around $800 to $1,500 a year.

 

A battery plugs that leak. And with the federal rebate currently covering roughly 30 per cent of the cost, plus flexible plans like Spiring Energy's that slash the upfront price and add monthly electricity credits on top — there has never been a better window to make your solar work as hard as it should.

 

Find your tier and get a quote — it takes under a minute, and there is no obligation.

 

Or read more on our blog for deep dives on rebates, VPPs, and battery comparisons.