Solar Bifacial Gain Calculator (Australia)
Estimate the rear-side bifacial gain for an Australian PV system from bifaciality factor, albedo, mounting height and GCR — and convert to extra kWh and AUD value at CEC tariffs.
Solar Bifacial Gain Calculator
How to use this calculator
This tool models the rear-side energy contribution of a bifacial PV system at Australian conditions. The default 6.6 kWp / 9,240 kWh per year reflects a typical north-facing residential install in NSW or Victoria per the CEC Solar PV Yield Calculator (1,400 kWh/kWp). Adjust the inputs for your specific configuration; the calculator multiplies the rear-side gain against the front-side production and the AER tariff to produce annual and 25-year lifetime values in AUD.
- System size (kWp) — Front-side STC rating.
- Annual front-side yield (kWh) — CEC PV-Vault calculator or PVOutput.org measured data.
- Bifaciality coefficient — Datasheet φ-factor (75–85% for current CEC-approved bifacial modules).
- Ground albedo — 0.22 grass, 0.30 dry pasture, 0.38 red sand, 0.55 white Colorbond.
- Module elevation (m) — 0.05–0.10 m typical pitched roof; 0.9–1.2 m residential ground-mount.
- GCR — Typical Australian ground-mount 0.40–0.45.
- Mismatch loss — 1.5% per the CEC PV Module Performance Bulletin No. 14.
- Tariff (A$/kWh) — Default A$0.32, the AER 2025 default market offer; reduce to A$0.05 if you self-consume nothing and export everything at feed-in.
Reference test — 6.6 kWp ground-mount, Wagga Wagga NSW
Inputs: 6.6 kWp Trina Vertex S+ 440W Bifacial, 9,240 kWh/yr front, φ = 80%, albedo 0.22 (dry grass), elevation 1.0 m, GCR 0.40, mismatch 1.5%, tariff A$0.32.
- view_factor = 0.5 × (1 − 0.40) × tanh(1.0 / 1.5) = 0.1748
- rear_fraction = 0.22 × 0.1748 = 3.85%
- bifacial_gain = 0.0385 × 0.80 × 0.985 = 3.03%
- extra_kWh = 9,240 × 0.0303 = 280 kWh/year
- extra_value = 280 × A$0.32 = A$89.60/year
- 25-year value = A$2,240
Same system on a Northern Territory cattle station with red sand (albedo 0.38) jumps to bifacial_gain 5.24%, extra 484 kWh/year, A$155/year, A$3,873 over 25 years.
Bifacial gain by Australian install type
| Configuration | Albedo | Elevation | GCR | Typical gain |
|---|---|---|---|---|
| Pitched colorbond roof, dark | 0.12 | 0.08 m | 0.55 | 0.2–0.4% |
| Pitched colorbond roof, light | 0.55 | 0.08 m | 0.55 | 1.0–1.8% |
| Pitched terracotta tile | 0.22 | 0.10 m | 0.55 | 0.4–0.7% |
| Commercial flat metal, white | 0.55 | 0.40 m | 0.55 | 4.5–6.5% |
| Carport, concrete | 0.30 | 2.5 m | 0.35 | 7.5–10% |
| Ground-mount, irrigated grass | 0.22 | 1.0 m | 0.40 | 3.0–4.5% |
| Ground-mount, dry paddock | 0.30 | 1.0 m | 0.40 | 4.5–6.0% |
| Ground-mount, NT red sand | 0.38 | 1.0 m | 0.40 | 5.5–7.5% |
| Single-axis tracker, red sand | 0.38 | 1.5 m | 0.35 | 9–13% |
Decision rule for Australian residential
The 2026 EnergyMatters and SolarQuotes shop-and-compare premium for bifacial over monofacial Tier-1 modules is A$45–A$80 per panel — A$675–A$1,200 on a typical 15-panel 6.6 kWp system. For most pitched-roof homes the 25-year lifetime value calculated above is well under that premium, so monofacial is the cheaper economic choice. Switch to bifacial when:
- Your roof is light-coloured Colorbond (Surfmist, Classic Cream) — push gain over 1.5%.
- The system is ground-mounted with at least 0.9 m clearance.
- You live in inland WA, NT, or far-north QLD where the dry-season albedo is consistently above 0.30.
What the CEC Design Certificate must show
CEC accreditation rules (Solar Accreditation Australia v2024) require any bifacial install to document on the certificate of compliance:
- Module bifaciality coefficient from the IEC TS 60904-1-2 test report
- Site albedo value and source (visual inspection, CSIRO map, or measurement)
- Rear-side clearance distance (rear glass to ground or reflecting surface)
- Updated string-voltage calc reflecting the combined front+rear Voc per AS/NZS 5033 §5.3
Installers that omit these face Solar Accreditation Australia audit non-conformance and potential STC clawback by the Clean Energy Regulator.
Sources
Clean Energy Council Approved Modules List, January 2026 edition; CEC Design Guidelines for Grid-Connected Solar PV Systems v9 (2024); CEC PV Module Performance Bulletin No. 14 (2023) Bifacial Modules; AS/NZS 5033:2021 (PV Array Installation); AS/NZS 4777.1:2016 (Grid Connection Inverter Systems); AS/NZS 3000:2018 (Wiring Rules); Solar Accreditation Australia Bifacial Annex 2024; AER Default Market Offer Determination 2025; CSIRO Atmospheric Composition Annual Report 2023 (Surface Albedo Map); Clean Energy Regulator SRES Eligibility Determination 2024; NREL TP-5K00-79233 Bifacial PV Performance Modeling; IEC TS 60904-1-2:2019; Trina Vertex S+ TSM-NEG9R.28 Bifacial datasheet rev 1.3; Jinko Tiger Neo N-type Bifacial datasheet 2024; LONGi Hi-MO 7 Bifacial datasheet rev 2.1; JA Solar Bifacial DeepBlue 4.0X datasheet 2024; SunWiz Australia Solar Insights 2024 Q4. Reach contact@solarcalculatorhq.com for site-specific design questions.