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The federal battery discount, a granny flat and a factory-built home

From Modular Living Australia — the independent knowledge base Last updated: 8 Oct 2026

The federal Cheaper Home Batteries Program gives a discount of around 30% on the upfront cost of an eligible battery of 5 kWh to 100 kWh installed from 1 July 2025, delivered through small-scale technology certificates.^[1][2] Only one battery system per premises is eligible, for the first installation, and it must be connected to a new or existing solar PV system.^[2][3][4] Whether a granny flat on the same lot counts as separate premises is not answered by the sources compiled here.

The federal battery discount is now large enough to change a project budget, and it lands squarely on the kind of build this site covers: a new dwelling, often small, often with solar already in the plan. But the program is built around a word — premises — that does not map cleanly onto a backyard with two homes on it, or onto a dwelling designed to be moved.

This page sets out what the published sources say, and is equally clear about the question they do not answer.

What the program does §

Households, businesses and community organisations can get a discount of around 30% on the upfront cost of installing a small-scale battery system between 5 kWh and 100 kWh. It is delivered through the creation and trading of small-scale technology certificates under the Small-scale Renewable Energy Scheme, rather than as a cash payment.^[1] In practice the retailer or installer takes the certificates and passes the value through as a reduction on your invoice.^[4]

The discount is not fixed. It is to be reviewed at least annually and will decrease over time until 2030, in line with falling battery prices.^[1] On 13 December 2025 the government announced an expansion from original estimates of $2.3 billion to an estimated $7.2 billion over four years, and amendments to the Renewable Energy (Electricity) Regulations 2001 were finalised on 5 February 2026, with two changes commencing 1 May 2026. The eligibility criteria themselves did not change on that date.^[1][2]

The eligibility rules that matter for a new build §

A registered certificate agent states that systems may be on-grid or off-grid, and that on-grid systems must be virtual power plant capable — commercial guidance from a business that trades certificates, not independent survey data.^[5]

The granny flat question §

Here is the difficulty. The regulator's position is that only one solar battery system is eligible for certificates per premises, and that additional batteries are not eligible after the first claim. It contrasts this explicitly with solar PV, which can claim multiple times up to 100 kW at a site, while a battery is eligible at each premises once only.^[3]

So: if you already have a battery on your house and you then build a secondary dwelling in the backyard, is that new dwelling a separate premises with its own entitlement, or the same premises that has already claimed?

The published sources do not answer this directly. What they do offer is a hint about how the department reads the word. Eligibility applies to the owner of the battery at the premises, and the department says this may include embedded networks where several owners each reside in their own unit — described in the source as a premises — in a communal environment such as a retirement village.^[2]

That language points toward a separately occupied unit being capable of being its own premises. It does not say that a secondary dwelling on the same title, behind the same house, is one. Nor do the sources address whether separate metering, a separate national metering identifier, or a separate address changes the answer.

This site does not publish an answer it cannot source. If a battery for a granny flat or second dwelling is material to your budget, put the question to the Clean Energy Regulator and to your retailer in writing before you sign anything, and get the answer against your specific metering arrangement rather than in general terms.

Tiny homes and relocatable dwellings §

For a dwelling designed to be moved, the program has a direct conflict built into it.

A battery, once installed, should remain at the property for the duration of the warranty period or the end of 2030, whichever is later. A battery moved to another premises is no longer eligible, and will not be eligible to claim certificates if re-installed at a new property.^[3] Retailers are also expected to provide assurance that they believe the battery will be installed for permanent use and would not be moved or on-sold.^[2]

None of that prohibits a battery in a tiny home on wheels. It does mean that the discount is priced on an assumption of permanence, and that relocating the dwelling with the battery attached is a scenario the published rules treat as ending eligibility. If your plan involves moving the home — see moving a transportable home again and tiny house on wheels or fixed foundation — this belongs in the conversation before installation, not after.

Off-grid systems are within scope according to a registered agent's published summary,^[5] which matters for the rural and remote builds covered in off-grid power, water and wastewater for tiny homes.

Timing on a factory-built home §

Two dates control the outcome, and off-site construction pulls them apart.

The first is the certificate of electrical compliance, which is what dates the installation for the program.^[2] The second is the date you commit — deposit paid, factory slot booked, system specified. Because the discount steps down over time toward 2030,^[1] a battery specified in a contract this year and energised well into next year is not worth the same amount, and the difference falls on whoever the contract says it falls on.

There is a second question specific to modular construction that the sources do not resolve: where a battery is fitted in the factory rather than on site, the compliance certificate arrangements are not addressed in the published program material reviewed here. Most on-site electrical work — including connection, commissioning and the issue of the compliance certificate — happens after installation in any case. Ask the manufacturer to confirm in writing who issues the certificate, on what date, and who holds the certificate entitlement.

Contract mechanics for off-site work are covered in progress payments and off-site construction.

State programs on top §

The regulator notes that other battery programs may be available in your state or territory, and warns that some may not be available if you are claiming certificates under the federal scheme. It advises checking whether you can claim both.^[3] Stacking is not automatic, and assuming it is a common way to end up with a budget hole.

What is not covered here §

This page does not state the number of certificates a given battery attracts, or the dollar value of the discount for a specific system. Certificate values move with the market and the deeming arrangements, and publishing a figure here would date immediately.

It does not describe the two changes that commenced on 1 May 2026 in technical detail. The department confirms the eligibility criteria did not change,^[2] and the full criteria sit in the Renewable Energy (Electricity) Regulations 2001.^[1]

It does not answer whether a secondary dwelling constitutes a separate premises for the purposes of the one-per-premises rule. No primary source addressing that question was located, and the sources compiled here do not support an inference either way.

It does not cover state and territory battery schemes individually, virtual power plant contracts and what they oblige you to do with your stored energy, electrical safety and installation standards, or whether a battery is a sound financial decision for your household. It also does not cover the energy performance requirements that apply to the dwelling itself — those are at the 7-star NatHERS rule and energy efficiency and sustainability in modular homes.

References §