How the battery rebate is calculated, step by step

The battery rebate is not a fixed amount of money. It is a number of small-scale technology certificates (STCs) that your battery is entitled to create, which most people hand to the installer in exchange for a discount on the price. How many certificates depends on the battery's usable capacity and the date it is installed.^[1] The regulator's own calculator asks for exactly those two things and nothing else: no postcode, no brand, no price.^[4]

Step 1: find the usable capacity

Usable capacity is the energy the battery can actually discharge, the power a home can draw from it.^[1] It is usually lower than the figure on the label. An AlphaESS SMILE-G3 BAT-10.1P module is sold as 10.1 kWh but listed at 9.6 kWh usable on the Clean Energy Council's approved list,^[3] and the certificates follow the list. The label's nominal figure matters for one thing only: the battery must be 5 to 100 kWh nominal to be eligible at all.^[5]

Step 2: look up the factor for the install date

The STC factor is the number of certificates per usable kWh. It is 6.8 for batteries installed from 1 May to 31 December 2026, and falls every six months to 2.1 in the second half of 2030.^[2] Installed means the day the certificate of electrical compliance is issued; the step-down guide explains what that means for timing.

Step 3: apply the size taper

Since 1 May 2026 the factor is not applied evenly. The first 14 kWh of usable capacity earn it in full, every kWh from 14 to 28 earns 60% of it, and every kWh from 28 to 50 earns 15%. Capacity above 50 kWh earns nothing.^[1] Big batteries still earn more in total, but each extra kilowatt-hour is worth less than the one before it.

Step 4: round down

Partial certificates are dropped: the total is rounded down to a whole number, as it is for solar panels.^[1] It always costs less than one certificate, but it is why a careful calculation and a rough one can differ by $40.

Step 5: multiply by the certificate price

Each certificate sells for $40 through the government's STC Clearing House, a price fixed in regulation and quoted excluding GST.^[1] Certificates can also be sold on the open market, where the price moves with supply and demand, and the retailer may take administration fees out of the discount.^[1] So $40 is the ceiling for what reaches you, not a guarantee.

A worked example: three AlphaESS modules

• Usable capacity: three BAT-10.1P modules are listed at 28.7 kWh, not the 30.3 kWh their labels add up to.^[3]
• First 14 kWh at the full factor: 14 × 6.8 = 95.2 certificates.
• 14 to 28 kWh at 60%: 14 × 6.8 × 0.6 = 57.12.
• The last 0.7 kWh at 15%: 0.7 × 6.8 × 0.15 = 0.714.
• Total 153.034, rounded down to 153 certificates, which is $6,120 at $40. Certified on or after 1 January 2027, the same battery creates 128 certificates, or $5,120.

The taper shows up when you price each module separately. The first module alone creates 65 certificates ($2,600). The second takes the battery past 14 kWh and adds 51 ($2,040). The third adds 37 ($1,480), because most of it sits in the 60% band. That is worth knowing before you pay for the last module.

Check your quote in a minute

Ask each installer for two numbers: how many certificates the battery creates, and the price per certificate behind their discount. Multiply them. If the certificate count differs from the calculation above for your battery and date, ask which usable capacity and install date they used; if the price is well under $40, ask what the difference covers.

Usable capacity, install date, taper, round down, times the price: get the first two right and the rest is arithmetic.