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Home batteries

A home battery stores electricity so you can use it later. Most homes charge a battery from rooftop solar during the day and use the stored energy in the evening, although some batteries can also charge from the grid.

A battery can be added to an existing solar system, installed with new solar, or in some cases installed on its own — but a battery without solar may not qualify for some incentives, such as the national Cheaper Home Batteries Program, which requires connection to solar panels. Whether one makes sense depends on how much electricity you use in the evening, your solar system (if any), your electricity plan and whether you want backup during outages.

What it can do for you

  • Use more of your own solar electricity by shifting it into the evening and night.
  • Buy less electricity from the grid at the times it is most expensive on your plan.
  • Optionally keep selected circuits running in a blackout, if the system is designed and set up for backup.

How it works

AC-coupled and DC-coupled home batteries comparedLeft: an AC-coupled battery has its own battery inverter and joins the solar inverter on the household AC side; it is often simpler to add to existing solar, but stored solar goes through an extra conversion. Right: a DC-coupled battery shares a hybrid inverter with the panels on the DC side; it has fewer conversions and some designs can store solar that would otherwise be clipped, but retrofitting may mean replacing the inverter. Neither is always better.AC-coupledSolar panelsBatteryDCSolar inverterBattery inverterSwitchboardAC: home + gridOften simpler to add to existing solar.Stored solar: DC → AC → DC → AC.DC-coupledSolar panelsBatteryDCHybrid inverterSwitchboardAC: home + gridFewer conversions; may store clipped solar.Retrofit may mean replacing the inverter.
Technical details
AC-coupled batteries
An AC-coupled battery has its own inverter and connects on the household AC side. It is usually simpler to add to an existing solar system because the solar inverter can stay in place. Energy from solar is converted to AC and then back to DC to charge the battery, so there is an extra conversion step.
DC-coupled batteries
A DC-coupled battery connects to a hybrid inverter on the DC side, alongside the panels. Solar can charge it with fewer conversions, and some designs can capture solar energy that would otherwise be clipped by the inverter. It often suits a new solar and battery system, but retrofitting may mean replacing the existing inverter.
Neither option is always better
AC and DC coupling each have trade-offs in efficiency, cost, retrofit effort, backup design and warranty arrangements. The better choice depends on your existing equipment and goals.
Round-trip losses
Some energy is lost each time the battery charges and discharges. The amount you get back out is less than the amount you put in.
What sets a sensible battery size
Size follows from your evening and overnight use, how much spare solar you have in each season, the power (kW) your appliances draw at once, whether you want a backup reserve, and your tariff. A battery that fills on most days and is mostly used each evening is usually better matched than a larger one that rarely fills or empties.
Backup needs specific hardware and a reserve
For a battery to supply power in a blackout, the system needs backup-capable equipment, a way to safely disconnect the home from the grid, and wiring of the circuits to be backed up. You also need to keep some charge in reserve; a battery that has already been emptied in the evening cannot cover an outage.

Terms people often mix up

Installed (nominal) capacity vs usable capacity (kWh)
A battery's nameplate capacity is usually larger than the energy you can actually use, because some is held back to protect the battery. Compare usable capacity across quotes.
Battery power (kW) vs battery energy (kWh)
Energy (kWh) is how much the battery stores. Power (kW) is how fast it can charge or discharge. A battery with plenty of energy but low power may not be able to run several large appliances at once.
Grid import vs total consumption
A battery reduces how much electricity you buy from the grid; it does not reduce how much your home uses — and because of round-trip losses it slightly increases total energy handled.
Backup reserve
The share of charge kept aside for outages. A larger reserve improves outage cover but leaves less for everyday use.

Advantages and limitations

Advantages

  • Advantage: Lets you use solar electricity after the sun goes down.
  • Advantage: Can reduce how much electricity you import at peak times on a time-of-use plan.
  • Advantage: Can provide backup to selected circuits during outages when designed and configured for it.
  • Advantage: Some batteries can join a virtual power plant, which may provide extra credits under the provider's terms.

Limitations

  • Limitation: A battery is a significant purchase and its value depends heavily on your usage, plan and solar size.
  • Limitation: Blackout backup is not built in as standard; it needs extra equipment and a charge reserve.
  • Limitation: Usable capacity gradually declines with age and use, and warranties set conditions such as throughput limits.
  • Limitation: Round-trip losses mean some stored energy is lost.
  • Limitation: Joining a virtual power plant can mean the provider controls when your battery charges or discharges.
  • Limitation: Location matters: batteries need a suitable place that meets installation and safety rules.

Financial considerations

1. Quick estimate

Your postcode, yearly use, any solar you have, the battery size and quoted price, and the rates from your bill are enough for a first estimate.

Everything is calculated in your browser. Nothing you type here is sent to PlaceNest or anyone else, and you don't need an account. Fields marked as required are needed for the estimate.

Your home & usage

A recent electricity bill has everything this section needs.

Your home's 4-digit postcode — used to estimate sunshine and to find programs for your state or territory.

How would you like to tell us your electricity use?

Your retailer's app or bill may show it; or multiply the bill's 'average daily use' by 365. Main meter only — leave out a separately metered controlled load (e.g. off-peak hot water).

Your battery & quote

From the battery quote and data sheet.

A battery mostly stores spare solar. Without solar it can only shift cheaper grid power to dearer times.

The usable (not nominal) capacity on the data sheet or quote.

Continuous charge / discharge power from the data sheet, e.g. 5 kW.

On the quote or data sheet.

The battery (and any extra equipment it needs) including GST, after any discount already applied.

Your tariff

Copy these from your bill or your retailer's plan details (the “energy fact sheet”), then tell us whether they include GST. We never fill in a price for you.
Your tariff type

Your bill says whether you pay one price all day or different prices at different times.

On your bill as “usage”, “general usage” or “anytime”, in c/kWh.

On your bill as “supply charge” or “daily charge”, in c/day.

What your retailer pays for solar you export (“feed-in tariff”), from your bill or plan. Enter 0 if you have none.

Do the rates you typed include GST?

Many bills print each rate WITHOUT GST and add GST in its own column (look for a “GST” column next to “Amount”). Choose that option and we add 10% to the usage and supply rates — never to the feed-in rate, which has no GST.

PlaceNest assumptions in use — change in Customise: Usage pattern: Most use in the late afternoon and evening · Heating and cooling: No big seasonal change.

2. Your estimated results

Fill in the quick estimate and press Calculate. Your estimate appears here — it stays in this browser.

3. Customise — detailed settings (optional)

Every setting below already has a value the estimate can use. Open a section to check it against your bill, quote or data sheet — anything you type replaces the PlaceNest assumption or modelling default.

Electricity tariff details (time-of-use times)

Only needed for a time-of-use tariff: choose “Time of use” in the quick estimate, then set your peak, shoulder and off-peak times here. Your usage, supply and feed-in rates and the GST question are in the quick estimate.

Usage pattern
When and how you use electricity changes how much solar or stored energy you use yourself.

This picks an estimated daily pattern. Your real pattern changes how much solar you use yourself. Left on the PlaceNest assumption, we use “most use in the late afternoon and evening”.

Electric heating or air-conditioning shifts use between seasons. Left on the PlaceNest assumption, we use “no big seasonal change”.

e.g. 15 if you'll add electric heating, −10 if you're cutting back. 0 means no change.

Your existing solar

Tick “I already have solar panels” in the quick estimate to describe them here (roof direction, tilt, shade and inverter).

How the battery runs, backup & VPP
How the battery is run

0 if you don't need backup. Kept charge isn't used to cut your bill.

Only an amount you've actually been offered — we never assume one.

Battery performance, warranty & replacement
PlaceNest modelling defaults, pre-filled — check the battery data sheet and warranty.

Some programs use the nameplate figure.

Energy back out ÷ energy in. PlaceNest modelling default 90% — check the data sheet.

PlaceNest modelling default 5%.

PlaceNest modelling default 2% — check the warranty's end-of-warranty capacity.

From the warranty document. PlaceNest modelling default 10 years.

Optional. Leave it unticked and the results assume the battery keeps working; either way, “What if the assumptions change?” shows the result if it has to be replaced when the warranty ends.

Future price changes
Nobody knows future prices — try other values and compare.

Nobody knows future prices. PlaceNest modelling default 3% — try other values.

Kept separate from electricity prices: feed-in rates have been falling. PlaceNest modelling default 0% (today's rate held).

Incentive eligibility
Optional. Incentives are only taken off the price when PlaceNest has verified the program and you clearly meet its rules.

Programs have date rules. Leave blank to use today.

If your quote shows the price of small-scale technology certificates (STCs), enter it. PlaceNest never assumes a market price.

Most programs require an accredited installer — ask for their accreditation number.

Only some programs have income limits. It stays in your browser.

Finance, maintenance & comparison period
How the money adds up over the years. A loan changes when you pay — it is financing, not a saving.

PlaceNest modelling default: 15 years.

How much less a dollar in future is worth to you than today. PlaceNest modelling default 5%.

Any servicing cost you expect. 0 if none.

Optional. Enter the terms from a real loan offer.

Government incentives & finance

PlaceNest hasn't verified any current government incentives yet, so none are listed here and none are taken off any PlaceNest estimate. Programs change often: check the official government source, and ask your installer what is already included in the quote.

How PlaceNest checks incentives

Is it likely to suit your home?

It may be worthwhile when

  • You already export a lot of solar during the day and use electricity in the evening.
  • You are on, or are willing to move to, a plan where evening grid electricity is relatively expensive.
  • Reliable backup for essential circuits matters to you and you are willing to pay for backup-capable equipment.
  • You plan to stay in the home for many years.

It may not be worthwhile when

  • You have little or no spare solar and are not planning to charge from cheaper off-peak grid electricity.
  • Your evening electricity use is low.
  • You expect to move soon.
  • There is no suitable, compliant location for the battery.
  • Your main goal is backup, but the quoted system is not designed or configured to provide it.

Common misconceptions

Myth: Every home battery keeps the power on in a blackout.
Reality: Only systems designed for backup do, and only for the circuits wired to the backup supply, and only while the battery has charge. Many batteries shut down with the grid unless backup equipment is installed.
Myth: A battery's advertised capacity is what I can use.
Reality: Usable capacity is usually less than nominal capacity. Compare usable kWh, and check the battery's power (kW) as well.
Myth: DC-coupled (or AC-coupled) is always better.
Reality: Each has trade-offs. DC coupling can avoid conversions and may capture clipped solar; AC coupling is usually simpler to add to an existing system.
Myth: A bigger battery is always better.
Reality: Extra capacity only adds value if it is regularly charged and used. In winter there may be little spare solar to fill it, and unused capacity still costs money. Shifting flexible usage into solar hours first often reduces the size you need.
Myth: A battery means I will never pay for electricity again.
Reality: Most homes still import some electricity, especially in winter, and pay daily supply charges.

Checklists

Before you buy

  1. Step 1: Look at your interval data or bills to see how much electricity you use in the evening and overnight.
  2. Step 2: Decide whether backup matters, and if so, which circuits you would want to keep running.
  3. Step 3: Compare usable capacity (kWh) and continuous power (kW) across quotes, not just nominal capacity.
  4. Step 4: Confirm the battery and inverter are on the Clean Energy Council approved product lists.
  5. Step 5: Check the installer's accreditation with Solar Accreditation Australia.
  6. Step 6: Ask whether the battery is AC- or DC-coupled and why that suits your existing equipment.
  7. Step 7: Read the warranty conditions, including retained-capacity and throughput terms.
  8. Step 8: If a virtual power plant is offered, read the terms on control, credits and leaving the program.
  9. Step 9: Get written quotes and check payment terms and cooling-off rights before signing.

At installation

  1. Step 1: The installation location meets the manufacturer's and Australian Standard requirements (for example clearances, ventilation and protection from sun and impact).
  2. Step 2: Network approval is in place where required.
  3. Step 3: Backup circuits, if any, are clearly labelled at the switchboard.
  4. Step 4: You receive the compliance certificate, product serial numbers, warranty registration and system settings, including the backup reserve.
  5. Step 5: The installer explains the shutdown procedure and how to change the reserve and operating mode.

Safety

Frequently asked questions

How big a battery do I need?

It depends on your evening and overnight use, how much solar you export, and whether you want backup. Bigger is not automatically better — a battery that rarely fills or empties adds cost without adding much value.

Should I change when I use electricity before buying a battery?

It usually helps to try first. Running flexible loads such as the dishwasher, washing machine, hot water heat pump or EV charging during solar hours uses solar directly without storage losses, and shows how much evening use is left for a battery to cover.

Will a battery work during a blackout?

Only if the system includes backup-capable equipment and wiring, and there is charge available. Ask the installer exactly which circuits will be backed up and how the backup reserve is set.

Can I add a battery to my existing solar?

Usually. An AC-coupled battery can often be added without changing the solar inverter. A DC-coupled battery may need a hybrid inverter. An installer can check compatibility.

What is a virtual power plant?

A program where a provider coordinates many home batteries and may charge or discharge yours under agreed terms, usually in return for credits. Read the terms on control, battery wear and exit conditions. In New South Wales, the NSW Government also runs a VPP incentive for eligible batteries — see its official page.

How long does a battery last?

Batteries degrade gradually. Warranties usually state a period and conditions such as a minimum retained capacity or a throughput limit — read them carefully.

Related topics

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Sources and review

Draft — pending human review

Not yet reviewed by a person. Programs, products and rules change — check the official source before you decide.

General information only. PlaceNest's energy guides, and any estimates or incentive lists, are general information and estimates — not personalised financial advice, and not a quote. Programs, prices and rules change: check the official sources, and get written quotes from accredited installers before you decide.

PlaceNest guides are general information, not financial advice. Whether solar, a battery or an EV charger pays off depends on your home, usage and prices.

Any incentive or finance details PlaceNest shows come from a reviewed list, each with its official source and the date it was checked; eligibility is decided by each program. See how incentives work and paying for an upgrade.

Not sure what size battery?

Compare several battery sizes, more solar panels and moving your EV or pool into solar hours, side by side, for your usage and tariff. Compare battery sizes and scenarios