Solar Self-Consumption Calculator (Australia)

How the calculator works

The Australian solar self-consumption calculator estimates two ratios — self-consumption (production used on site) and self-sufficiency (load met by solar) — and shows the dollar uplift a battery delivers under your state feed-in tariff.

Plug in seven figures and the tool returns annual generation, no-battery and with-battery self-consumption percentages, savings, and the battery uplift in AUD/year.

1. System size (kW) — DC nameplate. CER STC registrations for FY24 place the median new residential install at 9.0 kW DC; legacy installs cluster at 6.6 kW (the Solar Bonus Scheme cap).
2. Peak sun hours/day — annual state averages from Bureau of Meteorology / CEC data: Darwin 5.5, Brisbane 4.6, Perth 4.4, Sydney 4.2, Adelaide 4.4, Melbourne 3.8, Hobart 3.5, Canberra 4.5.
3. Annual usage (kWh) — your 12-month total. AER 2026 Default Market Offer benchmark household uses 6,800 kWh (NSW), 4,000 kWh (VIC), 4,600 kWh (SE QLD), 5,000 kWh (SA).
4. Retail rate ($/kWh) — AER 2026 DMO blended averages: NSW 34c, VIC 28c, SE QLD 31c, SA 38c, WA Synergy 32c, ACT 30c, TAS Aurora 28c.
5. Feed-in tariff ($/kWh) — AEMC 2026 state averages: NSW 6.0c, VIC 4.9c, QLD Solar Bonus closed (5c voluntary), SA AGL 5c, WA Synergy DEBS 2.5c peak / 10c off-peak, ACT ActewAGL 9.4c, TAS 8.929c.
6. Battery capacity (kWh) — usable. Tesla Powerwall 3 13.5 kWh, BYD HVM/HVS 7.7–22.1 kWh modular, sonnenBatterie 10 kWh.
7. Daytime overlap (%) — your unaided self-consumption percentage. Default 30%; raise to 40%+ if you run AC, pool pumps, or have an EV charging during solar hours.

How the math works

annual_kWh_produced  = system_kW × peak_sun_hours × 365 × 0.77
no_battery_self      = min(annual_use, annual_prod × overlap_pct/100)
battery_capture      = battery_kWh × 365 × 0.92 × 0.85
with_battery_self    = min(annual_use, no_battery_self + battery_capture, annual_prod)
self_consumption_pct = self_kWh / annual_prod × 100
self_sufficiency_pct = self_kWh / annual_use × 100
import_cost          = (annual_use − self_kWh) × retail_rate
fit_credit           = (annual_prod − self_kWh) × fit_rate
bill_with_solar      = max(0, import_cost − fit_credit)
annual_savings       = annual_use × retail_rate − bill_with_solar
battery_uplift       = with_battery_savings − no_battery_savings

The 0.77 system performance ratio derives from IEC 61724 and Clean Energy Council Approved Solar Retailer design assumptions. The 0.92 × 0.85 = 0.782 battery utilisation reflects LFP round-trip efficiency (92%) and usable depth-of-discharge (85%) typical for Tesla Powerwall 3, BYD Premium HVM, and sonnenBatterie. AS/NZS 4509 (stand-alone PV) and CEC’s battery sizing guideline both treat usable capacity as ~85% of nameplate.

Worked example: 6.6 kW PV in Sydney with 10 kWh Tesla Powerwall 3

• System: 6.6 kW DC, 4.2 PSH, AusGrid 34c retail, NSW 6.0c FIT
• Annual production: 6.6 × 4.2 × 365 × 0.77 = 7,791 kWh/yr
• Annual usage: 6,800 kWh (AER DMO NSW reference)
• No battery: self_consumed = min(6800, 7791×0.30) = 2,337 kWh
  • Self-consumption 30.0% · Self-sufficiency 34.4%
  • Exports 5,454 × 6c = $327 credit · Imports 4,463 × 34c = $1,517 cost
  • Bill with solar = max(0, $1,517 − $327) = $1,190 · Bill without solar = $2,312
  • Savings $1,122/yr
• With 10 kWh Powerwall 3: battery_capture = 10 × 365 × 0.92 × 0.85 = 2,857
  • self_consumed = min(6800, 2337 + 2857, 7791) = 5,194 kWh
  • Self-consumption 66.7% · Self-sufficiency 76.4%
  • Exports 2,597 × 6c = $156 · Imports 1,606 × 34c = $546
  • Bill with solar = max(0, $546 − $156) = $390
  • Savings $1,922/yr — battery uplift $800/yr

The Powerwall 3 at $14,500 installed minus the federal Cheaper Home Batteries rebate ($3,700 at current STC price for 10 kWh) nets ~$10,800. At $800/yr uplift, simple payback is 13.5 years — outside the 10-year warranty but inside Tesla’s 15-year design life. State top-ups (NSW Empowering Homes loan, ACT Next Gen Energy Storage rebate, SA Home Battery Scheme replacement) can shave another 2–4 years.

Worked example: same 6.6 kW PV in Perth on Synergy DEBS

• System: 6.6 kW DC, 4.4 PSH, Synergy 32c retail, DEBS 2.5c peak / 10c off-peak FIT (blended ~6c)
• Annual production: 8,164 kWh
• Annual usage: 5,400 kWh (Perth average)
• No battery: self 2,449 kWh (30%), savings $922/yr
• With 10 kWh battery: self 5,306 kWh (65%), savings $1,755/yr
• Battery uplift $833/yr — payback ~13 years on $10,800 net

WA’s Distributed Energy Buyback Scheme (DEBS) uses a time-of-export structure that pays 2.5c/kWh for 9am–3pm exports (when system inertia is challenged) and 10c/kWh for evening exports. A battery loaded during the cheap-export window and discharged in the evening can earn the 10c rate on remaining surplus, slightly improving uplift figures above.

Why the Australian self-consumption gap is so wide

Three factors make self-consumption the dominant Australian solar metric, more than any other comparable market:

1. Wide retail-vs-FIT gap — AER’s 2026 DMO average retail rate is 32c/kWh across the NEM; FITs average 5–6c. The 26–27c gap on every shifted kWh is the largest in any OECD market.
2. High midday solar penetration — Australia has the world’s highest per-capita rooftop solar (38% of dwellings as of CEC 2025 numbers). Network operators in SA, VIC, and QLD now apply midday export curtailment under emergency operating procedures during minimum demand events. Self-consumption directly avoids curtailment risk.
3. End of state Solar Bonus FITs — QLD Solar Bonus 44c, NSW Solar Bonus 60c, ACT 45.7c, VIC PFiT 60c all expired between 2016–2024. Households previously economically indifferent to self-consumption (44c FIT vs ~28c retail meant exports earned MORE than self-use) now face the inverse: exports worth 5–6c, self-use worth 28–38c.

Self-consumption levers that don’t require a battery

If a $10,000+ battery is out of reach, four no-storage levers raise self-consumption by 5–15 percentage points each:

1. Pool pump scheduling — variable-speed pool pumps (the dominant new-install option per Royal Life Saving 2024 data) consume 6–10 kWh/day. Setting the 6-hour cycle to 11am–5pm captures every kilowatt-hour from solar.
2. EV midday charging — a 7 kW Wallbox or Tesla Mobile Connector pulling 4–5 kWh/hour overlaps fully with solar. A daily 25 kWh top-up from solar saves $80–$100/month in EV charging costs versus off-peak grid charging.
3. AC pre-cooling — programming reverse-cycle AC to run 1pm–4pm (down to 22°C) and coast through evening peak shifts 4–6 kWh/day. Particularly effective in QLD, SA, NSW, and WA summer load profiles.
4. Hot-water diverters — Catch Power Green, Reposit Power, and Fronius Smart Meter setups route solar surplus to electric storage HWS. Captures 6–10 kWh/day for a $400–$700 retrofit.

Model the bill impact in our solar feed-in tariff calculator and the battery-specific payback in the solar battery ROI calculator.

State self-consumption snapshot (Q2 2026)

Source: AER Default Market Offer 2026, AEMC Residential Electricity Price Trends 2025, state regulator FIT tables.

Sources

• Clean Energy Regulator, Small-scale Technology Certificate registrations 2024 and Cheaper Home Batteries Program rules (1 July 2025).
• Clean Energy Council, Approved Solar Retailer design guidelines and Battery Buyers Guide 2025.
• Australian Energy Regulator (AER), Default Market Offer 2026 determination.
• Australian Energy Market Commission (AEMC), Residential Electricity Price Trends 2025.
• SunWiz, Australian Battery Market Report 2024.
• Bureau of Meteorology, Solar Irradiance Climate Atlas.
• AS/NZS 4509 Stand-alone Power Systems and CEC Battery Sizing Guideline.

Want to size the array or compare lease vs buy financing? Use our how many solar panels do i need calculator and solar lease vs buy calculator.