If a battery makes sense for your home anyway, buying before 1 January 2027 is worth roughly $400 to $600 on a typical system. If it does not make sense, no discount fixes that. At the time of writing the Cheaper Home Batteries Program factor drops from 6.8 to 5.7 on the first day of the year, and the STC discount shrinks with it.
The deadline is real, but it is a modest one, and rushing is the more expensive mistake. Here is how to weigh it.
What changes on 1 January 2027
The discount is the number of STCs the battery creates multiplied by the market price of an STC. The number is set by usable kWh, a size band structure, and a factor that falls over time. For installs from 1 May 2026 the factor is 6.8. From 1 January 2027 it is 5.7 and from 1 July 2027 it is 5.2, and it keeps stepping down every six months to 2030. The STC spot market has been roughly $38 to $40, and the clearing house ceiling is $40.
The numbers
| Usable kWh | STCs at 6.8 | STCs at 5.7 | Difference at $38 |
|---|---|---|---|
| 5 | 34 | 28.5 | about $209 |
| 10 | 68 | 57 | about $418 |
| 14 | 95.2 | 79.8 | about $585 |
| 20 | 119.7 | 100.3 | about $737 |
| 28 | 152.3 | 127.7 | about $935 |
The bands matter: above 14 kWh each extra kWh earns only 60 per cent of the factor, and above 28 kWh only 15 per cent. See the 2026 changes for the structure. These figures are illustrations; certificates round down and the STC price moves daily.
So the cost of waiting past New Year is somewhere between a few hundred and under a thousand dollars for most households. That is real money, but it is smaller than a typical difference between two installer quotes.
Reasons to move before the end of the year
- You already know the battery suits you. You have solar, a decent evening load, and a bill you want to cut.
- You have a quote you trust. The installer is accredited, the model is on the approved list, and the quote shows the discount separately.
- A state or retailer incentive is time-limited. If you can add a VPP sign-up payment or a state scheme, check whether it has a cut-off. See can you stack battery rebates.
- Installer lead times are short. Late in the year, good installers fill up.
Reasons to wait
- You do not have solar yet, and the right order is to size solar first.
- The quote does not feel right. A rushed decision on an unclear price removes the savings you were chasing.
- Battery prices are falling. If the hardware price drops by more than the discount does, waiting can be neutral. That has been the trend, but it is not a guarantee.
- Your usage is low. A small household with daytime consumption might gain little from storage.
The date traps
- Contract date is not install date. If you sign in November and the install happens on 6 January, the 5.7 factor applies.
- Delays happen. Stock, network approval and weather can push a job into the new year. Ask the installer what happens to the price if the install slips.
- Cut-offs for the end of the year. Installers often have a last date for installs that will land before 1 January. Ask for it.
A simple decision rule
- Would you buy this battery in 2027 at the 2027 price? If yes, a December install is a bonus, not a reason.
- Is the saving from beating the date more than 5 per cent of the net price? If not, do not trade quality for speed.
- Can the installer commit in writing to a date and show what happens if it slips? If not, treat the deadline as a risk.
What about installers?
Installers carry the discount, so the January step hits margin on any job sold at the old factor and installed after it. Contract wording that refers to the factor in force on the installation date protects you, and so does choosing a trader that pays quickly, as covered in how long STC payment should take.
Worked example: two households
Household A has 6.6 kW of solar, an evening load of about 12 kWh and a quote for a 13 kWh usable battery. At a factor of 6.8 the battery creates 88 STCs, about $3,344 at $38. After 1 January the same battery creates 74 STCs, about $2,812. The difference is $532. If the battery costs $9,500 before the discount, the net price moves from about $6,156 to $6,688, or 8.6 per cent. For this household a December install is worth pursuing, provided the installer is solid.
Household B has no solar, a low evening load and a quote for a 10 kWh battery. The discount difference is about $418, but without solar the battery would mostly charge from the grid. The right sequence is solar first, then the battery. The January step is a small cost compared with buying the wrong system.
Will the price of batteries fall instead?
Battery hardware prices have fallen over recent years and may continue to. If hardware drops by 5 per cent in the first half of 2027, that could offset some or all of the lower discount. Nobody can promise that. The discount step is certain, the price movement is not, and that is why we suggest deciding on the merits of the system.
What if you miss the date
Missing 1 January is not a disaster. The factor steps down again on 1 July 2027 and every six months to 2030, so the discount does not vanish; it shrinks. A household that installs in March 2027 still gets a meaningful discount, just a smaller one than in December. The sensible response to a missed date is to keep the same quote discipline: itemised STCs, usable kWh, a dated install and a conservative STC price. Do not let a deadline persuade you to skip any of those.
What to do next
- Get two or three quotes with usable kWh, STC count and discount value shown separately.
- Ask each installer for an installation date and the January price.
- Confirm the current factor and dates with the Clean Energy Regulator.
- Read the program overview and how the program works.
For the broader picture of battery certificates, see the battery STC page.