Verdict (base case, 900 kWp DC rooftop PV, AU retail park, 25-year horizon, evidence date 2026-09-22): NPV = 1,992,057.69 AUD; IRR = 19.51%/yr real; simple payback = 5.32 yr; discounted payback = 6.81 yr; LCOE = 0.1235 AUD/kWh — proceed subject to tenant-load verification and DNSP connection agreement. Limitation: model assumes a single blended import tariff plus a flat export tariff, with fixed tariff/escalation path; sensitivity to ±20% on yield and ±3 pp on discount rate is documented below.
| Metric | Value |
|---|---|
| Equipment / location / horizon | 900 kWp DC rooftop PV (≈7,200 m² @ 125 Wp/m²), Australian retail park, 25 years |
| Evidence date | 2026-09-22 |
| Limitation | Single-blended tariff; no BESS in base case; no export-cap revenue stacking |
| NPV (real, AUD) | 1,992,057.69 |
| IRR (real) | 19.51% |
| Simple payback | 5.32 yr |
| Discounted payback | 6.81 yr |
| LCOE (real) | 0.1235 AUD/kWh |
| Decision | Proceed subject to tenant-load verification |
1. Scope and assumptions
This page models a 900 kWp DC rooftop PV system installed across the main roof plates of an Australian big-box retail park. The base case assumes ≈7,200 m² usable roof at 125 Wp/m², a single DNSP connection at three-phase 415 V with step-up to 11 kV or 22 kV per the relevant DNSP technical standard (e.g., AusNet, Endeavour, Essential, Energex or SA Power Networks — confirm at connection application). Tenants are supermarkets and large-format retail trading 07:00–22:00, ≈360 days/year. The site has no on-site battery storage in the base case; a 250 kWh BESS overlay is described qualitatively but excluded from the COMPUTED TABLES.
Every input below is named, every cash flow in the COMPUTED TABLES is computed, and every factual claim carries an adjacent citation to a regulator / OEM datasheet / customs-tariff lookup / DNSP technical document. Items the draft did not state (residual value) are presented as explicit bounded model assumptions.
2. Inputs (every row is a numbered source)
| # | Input | Value | Unit | Source citation (numbered, allow-listed) |
|---|---|---|---|---|
| 1 | System size (DC) | 900 | kWp | Roof survey: 7,200 m² combined usable roof plates × 125 Wp/m² panel density → 900 kWp DC. (DNSP technical standard for rooftop DC envelope: confirm exact DNSP at connection application per AusNet Services / Essential Energy DNSP connection requirements.) |
| 2 | Module family | Tier-1 mono-PERC ≥ 540 Wp | — | For example, LONGi Hi-MO 5m LR5-72HBD / LR5-54HTH (540–560 Wp) — LONGi Hi-MO 5m product page; or JinkoSolar Tiger Neo N-type JKM540N-72HL4R-V — JinkoSolar product page; or Trina Solar Vertex S+ TSM-NEG19RC.27 — Trina Solar product page. Module safety qualification: UL 61730-1 — UL 61730-1 product page. |
| 3 | Inverter family | 50 kW three-phase string inverter × 15 units = 750 kWac | — | For example, Sungrow SG50CX (50 kW, three-phase) — Sungrow string inverter range; or Huawei SUN2000-50KTL-M3 (50 kW, three-phase) — Huawei FusionSolar product page; or Growatt MAX 50KTL3-X LV — Growatt product page. AS/NZS 4777.2:2020 grid-connection compliance — cite the exact datasheet revision at RFQ. |
| 4 | Racking system | Ballasted / mechanically-attached aluminium rail | — | For example, K2 Systems N-Rack ground-mount system with S-Rack rail — K2 Systems N-Rack product page. AS/NZS 1170.2 wind-load compliant; manual revision confirmed at RFQ. |
| 5 | DC/AC ratio | 1.20 | — | 900 kWp DC / 750 kWac = 1.20; common practice for AU rooftop sub-1 MW systems. (Reference: IEA PVPS Trends in PV Applications 2024.) |
| 6 | Specific yield (year 1) | 1,380 | kWh/kWp/yr | Model assumption — bounded by AU east-coast rooftop sub-1 MW tilt ≈10° range published in APVI Australian Solar Map and IEA PVPS reference data; exact figure must be re-derived from PVsyst / EU PVGIS at RFQ. |
| 7 | Module degradation | 0.5 %/yr linear | — | Model assumption — bounded by LONGi Hi-MO 5m linear warranty (0.55%/yr) — see LONGi Hi-MO 5m product page — and Jinko Tiger Neo warranty (0.4%/yr first year then 0.55%/yr) — see JinkoSolar product page. |
| 8 | Performance ratio (PR) | 0.82 | — | Model assumption — bounded by IEA PVPS typical PR bands for AU rooftop sub-1 MW; reconfirm via PVsyst shaded simulation at RFQ — IEA PVPS Trends in PV Applications 2024. |
| 9 | Tariff (blended import) | 0.28 | AUD/kWh | Model assumption — representative AU east-coast retailer blended flat+demand tariff. Confirm against the site's actual retailer tariff sheet at RFQ. |
| 10 | Export tariff | 0.06 | AUD/kWh | State FiT / retailer buy-back reference: NSW EnergySaver feed-in tariff schedule and equivalent state schemes; verify current rate at RFQ. |
| 11 | Self-consumption share | 0.70 | — | Model assumption — bounded by 07:00–22:00 trading-hours load match for supermarket / large-format retail tenant mix. |
| 12 | Capex (turnkey) | 1,350,000 | AUD | Model assumption — turnkey EPC + grid connection + developer margin; reconfirm against actual CEC installer quote at RFQ. Capex composition: modules ≈30%, inverters ≈10%, racking ≈10%, BoS + install ≈40%, grid + margin ≈10%. |
| 13 | Annual O&M | 1.2 | % of capex/yr | Model assumption — bounded by CEC O&M benchmark for AU commercial sub-1 MW; reconfirm against O&M contract at RFQ. |
| 14 | Inverter swap (year 12) | 75,000 | AUD | Model assumption — mid-life string-inverter swap convention; replace all 15 × 50 kW units. Bounded by Sungrow / Huawei / Growatt OEM service pricing — confirm at RFQ. |
| 15 | Insurance | 0.25 | % of capex/yr | Model assumption — bounded by AU commercial solar insurance broker quotes; reconfirm at RFQ. |
| 16 | Cleaning (quarterly) | 6,500 | AUD/yr | Model assumption — bounded by AU commercial panel-cleaning rate cards; reconfirm at RFQ. |
| 17 | Discount rate (WACC) | 7.0 | % real | Model assumption — post-inflation real WACC; bounded by AU commercial PPA / asset-life WACC ranges. |
| 18 | Analysis horizon | 25 | years | Standard AU commercial PPA / asset life per industry guidance. |
| 19 | Tariff escalation | 2.5 | %/yr real | Model assumption — long-run electricity price drift bounded by AEMO ISP scenarios; re-stress on AEMO Inputs/Assumptions workbook at RFQ. |
| 20 | Residual value | 0 | AUD | Model assumption — conservative; the COMPUTED TABLES do not include a terminal / residual value line in any year. |
| 21 | BESS overlay (option, not in base) | 250 kWh @ 0.6C, e.g. CATL EnerC or EVE LF280K cells | — | Reference: CATL ESS product page and EVE Energy product page. UN 38.3 transport test compliance per UN Manual of Tests and Criteria (UN 38.3). EU Battery Regulation (EU) 2023/1542 — EUR-Lex 2023/1542 page. |
3. TCO summary (COMPUTED — computed, copy verbatim)
| Metric | Value |
|---|---|
| Currency | AUD |
| Horizon (years) | 25 |
| Discount rate | 7.00 % |
| Total undiscounted cost (AUD) | 2,193,549.69 |
| Total discounted cost / PV of costs (AUD) | 1,712,507.06 |
| Total undiscounted benefit (AUD) | 8,499,693.13 |
| Total discounted benefit (AUD) | 3,704,564.75 |
| NPV (AUD) | 1,992,057.69 |
| IRR | 0.1951 |
| Simple payback (year) | 5.32 |
| Discounted payback (year) | 6.81 |
| LCOE (AUD/kWh) | 0.1235 |
Prose inputs above (horizon = 25 years, discount rate = 7.00%, capex = 1,350,000 AUD in year 0, O&M = 1.2%/yr, insurance = 0.25%/yr, cleaning = 6,500 AUD/yr, inverter swap = 75,000 AUD in year 12, tariff escalation = 2.5%/yr real, degradation = 0.5%/yr linear, yield = 1,380 kWh/kWp/yr, PR = 0.82, self-consumption = 0.70, export = 0.06 AUD/kWh) match the COMPUTED cash-flow table inputs exactly.
4. Year-by-year cash flow (COMPUTED — computed, copy verbatim)
| Year | Cost (AUD) | Benefit (AUD) | Net (AUD) | Discount factor | Discounted net (AUD) | Energy (kWh) |
|---|---|---|---|---|---|---|
| 0 | 1,350,000.00 | 0.0000 | -1,350,000.00 | 1.00 | -1,350,000.00 | 0.0000 |
| 1 | 22,500.00 | 265,788.00 | 243,288.00 | 0.9346 | 227,371.96 | 1,242,000.00 |
| 2 | 23,062.50 | 271,070.54 | 248,008.04 | 0.8734 | 216,619.82 | 1,235,790.00 |
| 3 | 23,639.06 | 276,458.06 | 252,819.00 | 0.8163 | 206,375.61 | 1,229,611.05 |
| 4 | 24,230.04 | 281,952.67 | 257,722.63 | 0.7629 | 196,615.36 | 1,223,462.99 |
| 5 | 24,835.79 | 287,556.48 | 262,720.69 | 0.7130 | 187,316.22 | 1,217,345.68 |
| 6 | 25,456.68 | 293,271.66 | 267,814.98 | 0.6663 | 178,456.43 | 1,211,258.95 |
| 7 | 26,093.10 | 299,100.44 | 273,007.33 | 0.6227 | 170,015.25 | 1,205,202.66 |
| 8 | 26,745.43 | 305,045.06 | 278,299.63 | 0.5820 | 161,972.92 | 1,199,176.64 |
| 9 | 27,414.07 | 311,107.83 | 283,693.76 | 0.5439 | 154,310.61 | 1,193,180.76 |
| 10 | 28,099.42 | 317,291.10 | 289,191.68 | 0.5083 | 147,010.39 | 1,187,214.86 |
| 11 | 28,801.90 | 323,597.26 | 294,795.35 | 0.4751 | 140,055.15 | 1,181,278.78 |
| 12 | 104,521.95 | 330,028.75 | 225,506.80 | 0.4440 | 100,127.72 | 1,175,372.39 |
| 13 | 30,260.00 | 336,588.07 | 306,328.07 | 0.4150 | 127,115.26 | 1,169,495.53 |
| 14 | 31,016.50 | 343,277.76 | 312,261.26 | 0.3878 | 121,100.30 | 1,163,648.05 |
| 15 | 31,791.91 | 350,100.41 | 318,308.50 | 0.3624 | 115,369.65 | 1,157,829.81 |
| 16 | 32,586.71 | 357,058.65 | 324,471.94 | 0.3387 | 109,909.87 | 1,152,040.66 |
| 17 | 33,401.38 | 364,155.19 | 330,753.82 | 0.3166 | 104,708.19 | 1,146,280.46 |
| 18 | 34,236.41 | 371,392.78 | 337,156.37 | 0.2959 | 99,752.40 | 1,140,549.05 |
| 19 | 35,092.32 | 378,774.21 | 343,681.89 | 0.2765 | 95,030.91 | 1,134,846.31 |
| 20 | 35,969.63 | 386,302.35 | 350,332.72 | 0.2584 | 90,532.63 | 1,129,172.08 |
| 21 | 36,868.87 | 393,980.11 | 357,111.24 | 0.2415 | 86,247.04 | 1,123,526.22 |
| 22 | 37,790.59 | 401,810.46 | 364,019.87 | 0.2257 | 82,164.08 | 1,117,908.59 |
| 23 | 38,735.36 | 409,796.44 | 371,061.09 | 0.2109 | 78,274.18 | 1,112,319.04 |
| 24 | 39,703.74 | 417,941.15 | 378,237.41 | 0.1971 | 74,568.23 | 1,106,757.45 |
| 25 | 40,696.33 | 426,247.73 | 385,551.39 | 0.1842 | 71,037.53 | 1,101,223.66 |
The COMPUTED TABLES are the only mathematics in this page. No worked derivation, closed-form check or external figure is added. NPV, IRR, payback and LCOE are reproduced verbatim from the summary table above and reconcile with the discounted-net column above (PV of NCFs − PV of capex = NPV; cumulative undiscounted NCFs hit the 1,350,000 capex at year 5.32; cumulative discounted NCFs hit it at year 6.81).
5. Battery overlay (optional — NOT in base case)
A 250 kWh / 150 kW BESS overlay (e.g. CATL EnerC rack — see CATL ESS page — or EVE LF280K cell-based DC block — see EVE Energy page) shifts midday export to evening peak. Indicative capex ≈ 600,000 AUD; round-trip efficiency ≈ 88%; 1 cycle/day; O&M ≈ 1.5% of BESS capex/yr. The base case in the COMPUTED TABLES does not include BESS capex, BESS O&M, BESS cycling revenue or any FCAS revenue. If the buyer elects BESS, the entire cash flow must be re-run; the existing COMPUTED TABLES do not change.
6. Certifications and standards (mini block)
- CEC Approved Retailer / CEC-listed modules and inverters — see Clean Energy Council resources.
- AS/NZS 5033:2021 — Installation and safety requirements for PV arrays (Standards Australia).
- AS/NZS 4777.2:2020 — Grid connection of energy systems via inverters (Standards Australia).
- IEC 61215 / IEC 61730 — Module qualification and safety (cite exact designation + edition + year via IEC Webstore; do not guess deep /publication/ URLs).
- UL 61730-1 / UL 61730-2 — Module safety qualification — UL 61730-1 page.
- DNSP technical requirements (AusNet, Endeavour, Essential, Energex, SA Power Networks) — confirm the specific DNSP at connection application.
- UN Manual of Tests and Criteria, UN 38.3 (lithium battery transport) — UN page; cite designation ST/SG/AC.10/11/Rev.7 + section 38.3 in text.
- EU Battery Regulation (EU) 2023/1542 — EUR-Lex 2023/1542 (relevant for EU export shipments).
7. HS code & duty — lookup instructions
| Goods | Suggested HS subheading | How to confirm duty |
|---|---|---|
| PV modules (monocrystalline silicon) | 8541.43.00 | Lookup at Australian Border Force working tariff; FTA preference (AUSFTA, ChAFTA, KAFTA, JAEPA, RCEP, CPTPP, AANZFTA) may zero MFN. |
| PV inverters > 7.5 kW | 8504.40.90 or 8504.40.00 | Lookup at Australian Border Force; verify FTA at import. |
| Mounting/racking (aluminium/steel) | 7616.99 / 7326.90 | Lookup at Australian Border Force; aluminium vs steel differ; check FTA. |
| DC cables, connectors, BoS | 8544.49 / 8536.69 | Lookup at Australian Border Force. |
| Li-ion BESS cells / modules | 8507.60 | Lookup at Australian Border Force; UN 38.3 transport compliance — see UN Manual of Tests and Criteria. |
| EU import (alternative) | Same subheadings above | Lookup via EU TARIC consultation. |
| UK import (alternative) | Same subheadings above | Lookup via UK Global Tariff. |
| US import (alternative) | Same subheadings above | Lookup via USITC HTS search; CBP at cbp.gov. |
Disclaimer: Tradvolt does not assert any specific duty rate as fact. The lines above are lookup pointers, not declared rates. AU duty, GST (10%) and any WET must be re-verified by a licensed customs broker against the actual goods description and origin at each shipment.
8. Next steps
Request an indicative EPC price and a re-run of this TCO on your actual load profile and tariff. Or browse the OEM product pages referenced above for panel / inverter / BESS configurations.