Methodology

Every number on Big Aus is derived from publicly available data. This page documents the formulas, constants and sources we use. If any of these change, we update this page and link the change in the relevant page's changelog.

Cheaper Home Batteries Program (CHBP)

Formula (to 30 April 2026):
rebate = usable kWh × deeming factor × STC price

Formula (from 1 May 2026): full rate on the first 14 kWh of usable capacity; reduced rate on capacity above 14 kWh (exact bands pending CER publication — figures in our tables will be updated when bands are gazetted).

Constants currently used

• Deeming factor (pre-1 May 2026): 8.4
• Deeming factor (from 1 May 2026): 6.8
• STC spot price: AUD $38.00 (nominal, updated 2026-04-24)
• Eligible battery range: 5–100 kWh nominal capacity; STCs claimable on the first 50 kWh of usable capacity.
• Installer admin fees: typically 2–5% of STC gross value, not standardised across the industry.

Primary sources

• Clean Energy Regulator — program rules, deeming factors, approved-products list: cer.gov.au/batteries
• DCCEEW — eligibility rules: dcceew.gov.au
• STC spot prices — Demand Manager, Greenbank
• State schemes — NSW PDRS (energy.nsw.gov.au), WA Synergy Home Battery Scheme, ACT Sustainable Household Scheme.

What we don't account for (yet)

Stage A figures are postcode-agnostic at the STC-zone level. We do not yet model:

• DNSP-specific export limits that affect the economics of oversized solar arrays
• Time-of-use tariff windows (which affect the marginal value of a stored kWh)
• Virtual Power Plant revenue streams
• Installer-specific admin fees

These will ship with the Stage B full calculator. Subscribe on the solar rebate page to be notified.

Corrections

Spotted a methodology issue or a source we should be using? Email hello@bigaus.com. Corrections are published publicly with the change date noted.