If installing solar panels or a home battery has been on your household to-do list, December 31, 2026 is a date you need marked on your calendar.
Australia’s federal Small-scale Renewable Energy Scheme (SRES) is scheduled for its annual step-down on January 1, 2027. Systems installed after midnight on New Year’s Eve will generate fewer Small-scale Technology Certificates (STCs), resulting in a noticeably smaller upfront point-of-sale discount.
Here is a comprehensive guide to how the 2026–2027 rebate reductions work, how much money is at stake, and why simply signing a contract before December won’t protect your savings.
107 Days Left: Why 31 December 2026 Matters for Australian Solar & Battery Rebates
If solar panels or a home battery are on your 2026 to-do list, there is an important date you should know: 31 December 2026.
Australia’s federal Small-scale Renewable Energy Scheme (SRES) is already on a scheduled phase-down. From 1 January 2027, the solar PV deeming period falls from 5 years to 4 years, while the battery STC factor falls from 6.8 to 5.7.
That means waiting until 2027 can reduce the upfront incentive available for an eligible solar and battery installation.
And with only 107 days remaining until 31 December 2026, the bigger risk for homeowners isn’t just the rebate reduction — it’s leaving the decision until December and discovering there is no suitable installation date available before the deadline.
What Changes on 1 January 2027?
The federal incentive doesn’t disappear on 1 January 2027 — but the amount of support available per eligible installation decreases.
Two important changes affect homeowners installing solar and batteries around the 2026–2027 transition.
1. Solar PV: The Deeming Period Falls from 5 Years to 4
For eligible rooftop solar PV systems, the number of STCs is influenced by the system’s expected renewable electricity generation and the applicable deeming period.
The Clean Energy Regulator’s current schedule is:
Installation Year | Solar PV Deeming Period |
2025 | 6 years |
2026 | 5 years |
2027 | 4 years |
2028 | 3 years |
2029 | 2 years |
2030 | 1 year |
So a qualifying solar installation completed in 2026 receives a 5-year deeming period, while one installed in 2027 receives a 4-year deeming period.
In simple terms, moving from 2026 to 2027 reduces the deeming component from 0.5 to 0.4 — a 20% reduction in that component of the solar STC calculation.
2. Home Batteries: The STC Factor Drops from 6.8 to 5.7
The federal Cheaper Home Batteries Program uses STCs to provide an upfront discount on eligible battery installations.
For batteries installed between May and December 2026, the applicable STC factor is 6.8 STCs per kWh of usable capacity.
From 1 January 2027, it falls to 5.7.
Installation Period | Battery STC Factor |
Jan–Apr 2026 | 8.4 |
May–Dec 2026 | 6.8 |
Jan–Jun 2027 | 5.7 |
Jul–Dec 2027 | 5.2 |
Jan–Jun 2028 | 4.6 |
The government says the battery discount is designed to remain around 30% of the upfront installation cost and will decline over time as battery technology costs are expected to fall.
The important point for homeowners is simple: A battery installed in 2026 can attract more STCs than the same eligible battery installed in 2027.
Rooftop Solar PV: Deeming Period Drop
- How it works: Solar PV certificate calculations rely on a “deeming period”—the number of expected future generation years credited upfront as the SRES scheme counts down toward its 2030 sunset.
- The 2027 reduction: For systems installed in 2026, the deeming period is 5 years. On January 1, 2027, it drops to 4 years.
- The financial impact: This 1-year reduction produces approximately 20% fewer solar STCs. On a typical 6.6kW to 10kW residential system, this translates to losing $200 to $400+ in government-backed upfront discounts.
Home Battery Storage: Cheaper Home Batteries Factor Step-Down
- How it works: Under the federal Cheaper Home Batteries Program, battery installations generate STCs based on their usable storage capacity.
- The 2027 reduction: The battery STC factor steps down from 6.8 (applicable for May–December 2026) to 5.7 on January 1, 2027. This represents a ~16% drop in certificate creation before capacity tapering is applied.
- Capacity Tapering Rules: The federal program applies tiered support rates based on usable capacity:
- 0 to 14 kWh: 100% of the applicable STC factor.
- >14 to 28 kWh: 60% of the factor.
- >28 to 50 kWh: 15% of the factor.
- Above 50 kWh: No additional battery STCs.
Battery Capacity Tapering: Why Bigger Isn't Always Better
From 1 May 2026, the battery STC calculation applies different rates to different portions of usable battery capacity:
- 0–14 kWh: 100% of the applicable STC factor
- Above 14–28 kWh: 60% of the applicable factor
- Above 28–50 kWh: 15% of the applicable factor
- Above 50 kWh: no additional STCs
Importantly, the lower rate applies to the additional capacity within each band — not retrospectively to the entire battery.
This means homeowners shouldn’t automatically choose the biggest battery available simply to maximise the rebate.
The right battery size should be based on your household’s electricity consumption, solar generation, evening usage, backup requirements and expected financial return.
Combined System Impact
For homeowners installing a 10kW solar system paired with a 13kWh battery, the combined reduction between solar PV deeming drops and battery STC factor cuts represents a loss of $800+ in upfront government support compared to installing before the end of 2026.
How Much Could Waiting Until 2027 Cost?
The exact dollar difference depends on your system size, location, STC value and battery capacity, so there is no single rebate amount that applies to every Australian household. However, the change can be illustrated using a typical 13 kWh usable battery.
Example: 13 kWh Battery
Under the 2026 battery STC factor of 6.8:
13 kWh × 6.8 = 88.4 STCs
From 1 January 2027, the factor becomes 5.7:
13 kWh × 5.7 = 74.1 STCs
That’s a difference of approximately 14 STCs on the same 13 kWh usable battery.
The actual dollar impact depends on the STC value used by your installer at the time of installation. And remember: this is only the battery component.
If you are also installing solar PV, the solar deeming period simultaneously falls from 5 years in 2026 to 4 years in 2027.
The takeaway?
The longer you wait, the less generous the federal incentive structure becomes. Your system doesn’t become cheaper simply because you wait. The incentive attached to it can become smaller.
Why Contracts Do Not Lock In Your Rebate
One of the most common misconceptions among property owners is that accepting a quote or paying a deposit in late 2026 locks in 2026 rebate rates. It does not.
- The Installation Date Rule: Regulations stipulate that STC calculations are determined strictly by the physical installation and electrical sign-off date, not the contract signing date.
- Installer Bookings Fill Early: Reputable Clean Energy Council (CEC) accredited installers experience heavy demand in Q4. If installer calendars fill up and your physical installation spills into January 2027, you will receive the lower 2027 incentive rate regardless of when you signed.
- Grid and Network Requirements Can Add Time: Depending on your location, system design, inverter size and electricity distributor, additional network requirements or approvals may apply. This is another reason not to leave your installation until December. Your installer should confirm the applicable requirements for your property and allow sufficient time for any required network process before the installation date.
107 DAYS UNTIL THE 2026 DEADLINE
31 December 2026 is not a date to start looking for solar. It’s the date you’re trying to be installed by.
From 1 January 2027:
Solar PV: 5-year deeming period → 4 years
Battery: 6.8 STC factor → 5.7
If solar or a battery is already on your 2026 plans, start the process now — not in December.
2026 vs 2027: What's Changing?
Incentive | 2026 | From 1 Jan 2027 | What it means |
Solar PV deeming period | 5 years | 4 years | Lower solar STC entitlement |
Battery STC factor | 6.8 | 5.7 | Fewer battery STCs per kWh |
Battery support | Available | Available | Program continues, but support reduces |
Battery tapering | Applies | Applies | Larger batteries receive lower rates on additional capacity |
SRES | Continues | Continues | Incentive is reducing progressively toward 2030 |
The federal government confirms that battery support will continue through the Cheaper Home Batteries Program, but the STC factor declines over time. 2027 doesn’t mean “no rebate.” It means a smaller incentive than 2026.
Don't Wait Until December to Start
Here’s the biggest mistake homeowners can make: Treating 31 December as the date to order solar.
It isn’t. It’s the date you are trying to beat.
For an installation to qualify based on the 2026 rules, the system needs to be completed and capable of producing electricity in 2026. The Clean Energy Regulator states that a small-scale solar system must be complete and capable of producing electricity before STCs can be created. For grid-connected systems, the inverter does not necessarily need to be connected to the meter or main grid for the system to be considered complete.
That means homeowners need to allow time for:
- Choosing the right system
- Comparing quotes
- Confirming equipment availability
- Finalising system design
- Completing any required grid/network processes
- Scheduling the installation
- Completing installation and commissioning
- Completing the required electrical compliance documentation
The real deadline is earlier than 31 December
If you wait until December to begin the process, you may be putting your 2026 incentive at the mercy of installer availability, equipment supply and project scheduling.
December 31 should be your target completion date — not your shopping date.
With only 107 days remaining, now is the time to start comparing your options.
Step-by-Step Action Plan for Homeowners
To ensure your system is installed, tested, and certified before the December 31 cut-off, follow this target timeline:
- September – October (Compare Quotes & Confirm Accreditation): Request itemised proposals showing exact STC upfront discount calculations from accredited installers. Ensure all panels, inverters, and batteries are on the official approved product list.
- Late October – November (Finalise System Design & Grid Approvals): Lock in hardware models and submit grid connection applications promptly, allowing 3 to 5 weeks for network connection assessments if installing a system larger than 5kW. Right-size your battery storage to ensure optimal financial return under tapering rules.
- December (Physical Installation & Electrical Sign-off): Confirm in writing that your installer has secured a guaranteed installation window on or before December 31, 2026, to complete physical installation and electrical testing before the deadline.
Don't Let the Calendar Make the Decision for You
If you’ve already been thinking about solar or a home battery, you don’t need to rush into the first quote you receive. But you also don’t want to wait until December to begin. The 2026 incentive window is moving toward its scheduled step-down:
Solar PV: 5-year deeming period in 2026 → 4 years in 2027
Battery: 6.8 STC factor in May–December 2026 → 5.7 in January–June 2027
And once December installation calendars start filling up, your biggest problem may not be choosing a system — it may be finding an installation date before the 2026 incentive settings change.
Summary
The federal solar and battery rebates are not disappearing overnight, but their built-in annual phase-down means waiting until 2027 directly increases your out-of-pocket costs. Taking action early gives you ample time to evaluate equipment, obtain grid permissions, and secure your place on an installer’s calendar before the end-of-year deadline.
Thinking about solar or a battery?
Speak with AYKA Solar about your options now.
We’ll help you understand:
- What system size suits your home
- Whether adding a battery makes financial sense
- Your estimated 2026 STC incentive
- Your expected out-of-pocket cost
- Available battery options
- The installation timeline for your property
Don’t wait for December to find out what 2026 could have saved you. Get Your 2026 Solar & Battery Quote. Contact AYKA Solar today and secure your place in the installation pipeline before the end-of-year rush.
SOLAR REBATES ARE REDUCING FROM 1 JANUARY 2027
