The 2027 solar rebate drop is a one-fifth cut in certificates, which for a typical 6.6 kW system in a capital city is nine fewer STCs, or about $340 at a $38 spot price. For a mid-sized home battery the step-down on 1 January is about $570. Those are the numbers most households actually care about, and they are smaller than most headlines suggest.
The more useful picture is the whole glide path to 2030. Each year the deeming period loses a year, so the proportional cut gets steeper even though the dollar steps get smaller as systems earn fewer certificates. This page lays out the arithmetic so you can read it for your own system size and zone.
The deeming schedule and the percentage cut
| Install year | Deeming years | Change vs prior year |
|---|---|---|
| 2026 | 5 | n/a |
| 2027 | 4 | down 20% |
| 2028 | 3 | down 25% |
| 2029 | 2 | down 33% |
| 2030 | 1 | down 50% |
The scheme closes on 31 December 2030, so there are no deemed years after that. The zone rating multiplies the years, so the percentage cut is identical in every zone.
Dollar drop by system size
The tables use Zone 3 (rating 1.382) and a $38 spot price, which sits inside the roughly $38 to $40 range at the time of writing. STCs are rounded down.
| System | 2026 STCs | 2027 STCs | STCs lost | Value lost at $38 |
|---|---|---|---|---|
| 5 kW | 34 | 27 | 7 | $266 |
| 6.6 kW | 45 | 36 | 9 | $342 |
| 8 kW | 55 | 44 | 11 | $418 |
| 10 kW | 69 | 55 | 14 | $532 |
| 13 kW | 89 | 71 | 18 | $684 |
Worked example for the 8 kW row: 8 x 1.382 x 5 = 55.3, so 55 STCs; 8 x 1.382 x 4 = 44.2, so 44. The difference of 11 certificates at $38 is $418.
The same 6.6 kW system by zone
| Zone | Rating | 2026 | 2027 | 2028 | 2029 | 2030 |
|---|---|---|---|---|---|---|
| 1 | 1.622 | 53 | 42 | 32 | 21 | 10 |
| 2 | 1.536 | 50 | 40 | 30 | 20 | 10 |
| 3 | 1.382 | 45 | 36 | 27 | 18 | 9 |
| 4 | 1.185 | 39 | 31 | 23 | 15 | 7 |
By 2030 the same system earns about a fifth of what it does in 2026. In dollars at $38, that is about $1,710 in 2026 falling to about $340 in 2030 for Zone 3.
The battery step
For a battery, certificates equal usable kWh times the factor, which is 6.8 for 2026 installs and 5.7 from 1 January 2027 and 5.2 from 1 July 2027, then stepping down every six months to 2030.
| Usable kWh | 2026 STCs | 2027 STCs | Value lost at $38 |
|---|---|---|---|
| 10 | 68 | 57 | $418 |
| 13.5 | 91 | 76 | $570 |
| 20 | 136 | 114 | $836 |
| 30 | 204 | 171 | $1,254 |
Check the tier rules for larger sizes on the May 2026 changes answer before using the 20 or 30 kWh rows for a real quote, since the program has adjusted how larger capacities are treated. Our answer on the 5.7 factor covers the basics.
Is the drop a reason to rush?
Compare the drop with the spread between quotes. If your two best solar quotes are $900 apart, the $342 deeming loss is not the main decision. If one installer offers a firm December date, an approved battery, and a clear STC count, locking that in can make sense.
Rushing costs money in other ways: rushed installs have more failed photo checks and more rejected claims. See why claims get rejected. An installer who squeezes a dozen jobs into the last two weeks of December is more likely to cut corners than one working a normal schedule.
What about the STC price?
With the clearing house ceiling at $40, the spot price has been bounded for years. Fewer certificates created could in theory tighten the market, but a falling number of STCs does not lift the price above $40 because anyone can sell into the clearing house at that ceiling. Plan on the ceiling as your upper bound. Our pricing page shows the daily buy rates from our desk, and the what an STC is worth guide explains the gap between spot and clearing house.
How to read these tables for your own job
Pick your system size, multiply by the zone rating and the number of years. Round down. That is your STC count. Multiply by the price your installer or trader is crediting you, not by an advertised headline price. If the number on your quote differs from the formula, ask why.
Two details catch people out. First, the rounding is per claim, so a 6.7 kW system rather than a 6.6 kW one earns an extra certificate (46 rather than 45 in Zone 3 in 2026). Second, the zone is set by postcode, not by suburb folklore, so use the regulator’s postcode table. Our zone rating guide has a quick way to check.
What the percentages mean for installers
For an installer selling 40 systems a month at an average of 8 kW in Zone 3, the move from 2026 to 2027 removes 11 STCs per job, or 440 certificates a month. At $38 that is $16,720 a month in certificate value that either shows up as a lower discount to customers or is absorbed in margin. Installers who put the new numbers in their pricing early keep control of the conversation; those who leave it to January discover it in their cash flow.
It also raises the stakes on claim quality. With fewer certificates per job, each rejected or delayed claim hurts a larger share of the job’s margin. A compliance pre-check before lodgement is cheap compared with a month of waiting for a rejected claim to be fixed.
What to do next
- Use the tables to find your row and zone.
- Add the dollar drop to your timeline: if it is under your quote spread, choose on quality.
- Read the 2027 changes guide and the pillar page for STC trading.
- Installers: build the install-year assumption into your quote template, and check how it works for lodgement and settlement timing.