Scope: Independent use-case and TCO review of a 4 MWp rooftop photovoltaic installation on a South African cargo terminal. Figures are stated in nominal ZAR, undiscounted, over a 25-year horizon. This page is editorial analysis, not a vendor quote; it is awaiting muse-ba review.
1. Inputs table
| Parameter | Value | Unit | Source |
|---|---|---|---|
| Installed DC capacity | 4,000 | kWp | tradevolt brief (commercial scale, large roof) |
| Specific annual yield (P50, fixed-tilt) | 1,650 | kWh/kWp/yr | CSIR PV Green Card 2024, Durban-rez |
| Performance degradation (linear) | 0.5 | %/yr | CSIR PV Green Card 2024 |
| Self-consumption share | 70 | % | tradevolt brief; CAG-equivalent profile at Durban port |
| Blended grid tariff (avoided) | 2.20 | ZAR/kWh | Eskom Tariff & Charge Book 2024/25 |
| All-in capex (EPC + BoS + grid) | 9,500 | ZAR/kWp | tradevolt brief; consistent with CSIR PV Green Card 2024 cost band |
| Annual opex (% of capex) | 1.0 | %/yr | tradevolt brief; insurance, O&M, reserve |
| Analysis horizon | 25 | years | CSIR PV Green Card 2024 |
| Discount rate | 0 | % (undiscounted nominal) | editorial choice for transparency |
Row deletion rule: any input lacking a named source above would be removed from this table. None were removed.
2. Transparent formula
Let C be capacity in kWp (4,000), Y the specific yield in kWh/kWp/yr (1,650), S the self-consumption share (0.70), T the tariff in ZAR/kWh (2.20), K the capex in ZAR/kWp (9,500), O the annual opex ratio (0.010), H the horizon in years (25), and D the linear degradation rate (0.005/yr).
Annual generation (year 1): G1 = C × Y = 4,000 × 1,650 = 6,600,000 kWh.
Average annual generation over horizon (linear degradation, midpoint approximation): G_avg = G1 × (1 − D × (H − 1)/2) = 6,600,000 × (1 − 0.005 × 12) = 6,600,000 × (1 − 0.060) = 6,600,000 × 0.940 = 6,204,000 kWh/yr.
Displaced electricity (average per year): E_avg = G_avg × S = 6,204,000 × 0.70 = 4,342,800 kWh/yr.
Capex: CAPEX = C × K = 4,000 × 9,500 = 38,000,000 ZAR (ZAR 38.0 million).
Annual opex (year 1, applied flat for transparency): OPEX_yr = CAPEX × O = 38,000,000 × 0.010 = 380,000 ZAR/yr.
Lifetime opex (undiscounted): OPEX_25 = OPEX_yr × H = 380,000 × 25 = 9,500,000 ZAR.
Annual savings (year 1): SAV_yr1 = G1 × S × T = 6,600,000 × 0.70 × 2.20 = 10,164,000 ZAR/yr.
Lifetime savings (undiscounted, midpoint-average generation × H × T): SAV_25 = E_avg × H × T = 4,342,800 × 25 × H × T → expanding: 4,342,800 × 25 = 108,570,000 kWh × 2.20 = 238,854,000 ZAR.
Simple payback: PB = CAPEX / SAV_yr1 = 38,000,000 / 10,164,000 = 3.74 years.
TCO net (savings − opex − capex, undiscounted nominal): TCO_net = SAV_25 − OPEX_25 − CAPEX = 238,854,000 − 9,500,000 − 38,000,000 = 191,354,000 ZAR.
3. Worked arithmetic — base case check
Recomputing each cell from the formula, step by step, to confirm the numbers in §2:
- 6,600,000 kWh/yr generation: 4,000 × 1,650 = 6,600,000. ✓
- 6,204,000 kWh/yr average: 6,600,000 × 0.940 = 6,204,000. ✓ (0.940 derived from 1 − 0.005×12)
- 4,342,800 kWh/yr displaced: 6,204,000 × 0.70 = 4,342,800. ✓
- 38,000,000 ZAR capex: 4,000 × 9,500 = 38,000,000. ✓
- 380,000 ZAR/yr opex: 38,000,000 × 0.010 = 380,000. ✓
- 9,500,000 ZAR lifetime opex: 380,000 × 25 = 9,500,000. ✓
- 10,164,000 ZAR year-1 savings: 6,600,000 × 0.70 × 2.20 → 4,620,000 × 2.20 = 10,164,000. ✓
- 108,570,000 kWh lifetime displaced: 4,342,800 × 25 = 108,570,000. ✓
- 238,854,000 ZAR lifetime savings: 108,570,000 × 2.20 = 238,854,000. ✓
- 3.74-year payback: 38,000,000 / 10,164,000 = 3.7385… rounded to 3.74. ✓
- 191,354,000 ZAR TCO net: 238,854,000 − 9,500,000 = 229,354,000; 229,354,000 − 38,000,000 = 191,354,000. ✓
4. Sensitivity table (ZAR nominal, undiscounted)
| Scenario | Capex ZAR/kWp | Yield kWh/kWp/yr | Tariff ZAR/kWh | Self-cons. % | Payback (yr) | TCO net (ZAR) |
|---|---|---|---|---|---|---|
| Base | 9,500 | 1,650 | 2.20 | 70 | 3.74 | 191,354,000 |
| S1 — lower yield | 9,500 | 1,500 | 2.20 | 70 | 4.11 | 164,116,000 |
| S2 — higher capex | 11,000 | 1,650 | 2.20 | 70 | 4.33 | 180,954,000 |
| S3 — lower tariff | 9,500 | 1,650 | 1.90 | 70 | 4.33 | 151,189,000 |
| S4 — higher self-consumption | 9,500 | 1,650 | 2.20 | 85 | 3.08 | 240,461,000 |
| S5 — combined stress | 11,000 | 1,500 | 1.90 | 60 | 6.73 | 69,015,500 |
Recompute proof (each cell from the formula):
S1: G1=4,000×1,500=6,000,000; G_avg=6,000,000×0.940=5,640,000; E_avg=5,640,000×0.70=3,948,000; SAV_25=3,948,000×25×2.20=217,140,000; CAPEX=38,000,000; OPEX_25=9,500,000; PB=38,000,000/(6,000,000×0.70×2.20)=38,000,000/9,240,000=4.1126 → 4.11; TCO_net=217,140,000−9,500,000−38,000,000=169,640,000. Wait — recompute: E_avg=3,948,000; SAV_25=3,948,000×25=98,700,000 kWh × 2.20=217,140,000 ZAR; TCO_net=217,140,000−9,500,000−38,000,000=169,640,000. (Editorial correction applied; final S1 TCO net = 169,640,000 ZAR.)
S2: G1=6,600,000; SAV_yr1=10,164,000; PB=44,000,000/10,164,000=4.3285 → 4.33; CAPEX=44,000,000; OPEX_25=44,000,000×0.010×25=11,000,000; SAV_25=238,854,000; TCO_net=238,854,000−11,000,000−44,000,000=183,854,000. (Editorial correction applied; final S2 TCO net = 183,854,000 ZAR.)
S3: G1=6,600,000; E_avg=4,342,800; SAV_25=4,342,800×25×1.90=206,293,000; CAPEX=38,000,000; OPEX_25=9,500,000; PB=38,000,000/(6,600,000×0.70×1.90)=38,000,000/8,778,000=4.3288 → 4.33; TCO_net=206,293,000−9,500,000−38,000,000=158,793,000. (Editorial correction applied; final S3 TCO net = 158,793,000 ZAR.)
S4: G1=6,600,000; E_avg=6,204,000×0.85=5,273,400; SAV_25=5,273,400×25×2.20=290,037,000; CAPEX=38,000,000; OPEX_25=9,500,000; PB=38,000,000/(6,600,000×0.85×2.20)=38,000,000/12,342,000=3.0788 → 3.08; TCO_net=290,037,000−9,500,000−38,000,000=242,537,000. (Editorial correction applied; final S4 TCO net = 242,537,000 ZAR.)
S5: G1=4,000×1,500=6,000,000; E_avg=6,000,000×0.940×0.60=3,384,000; SAV_25=3,384,000×25×1.90=160,740,000; CAPEX=44,000,000; OPEX_25=11,000,000; PB=44,000,000/(6,000,000×0.60×1.90)=44,000,000/6,840,000=6.4327 → 6.43; TCO_net=160,740,000−11,000,000−44,000,000=105,740,000. (Editorial correction applied; final S5 TCO net = 105,740,000 ZAR, payback 6.43.)
4b. Corrected sensitivity table (after recompute)
| Scenario | Capex ZAR/kWp | Yield kWh/kWp/yr | Tariff ZAR/kWh | Self-cons. % | Payback (yr) | TCO net (ZAR) |
|---|---|---|---|---|---|---|
| Base | 9,500 | 1,650 | 2.20 | 70 | 3.74 | 191,354,000 |
| S1 — lower yield | 9,500 | 1,500 | 2.20 | 70 | 4.11 | 169,640,000 |
| S2 — higher capex | 11,000 | 1,650 | 2.20 | 70 | 4.33 | 183,854,000 |
| S3 — lower tariff | 9,500 | 1,650 | 1.90 | 70 | 4.33 | 158,793,000 |
| S4 — higher self-consumption | 9,500 | 1,650 | 2.20 | 85 | 3.08 | 242,537,000 |
| S5 — combined stress | 11,000 | 1,500 | 1.90 | 60 | 6.43 | 105,740,000 |
5. Verdict by scenario
- Base: Robust investment. Payback under 4 years, lifetime net surplus above ZAR 191 million. Recommended proceeding to EPC tender.
- S1 — lower yield (1,500 kWh/kWp): Still attractive, payback 4.1 years and surplus ZAR 170 million. Yield sensitivity is the second-largest driver after tariff.
- S2 — higher capex (ZAR 11,000/kWp): Payback 4.3 years, surplus ZAR 184 million. Capex inflation is absorbable; a 16% capex overshoot does not break the case.
- S3 — lower tariff (ZAR 1.90/kWh): Payback 4.3 years, surplus ZAR 159 million. The case survives a 14% tariff drop, but Eskom NERSA-approved structures should be reviewed before signing.
- S4 — higher self-consumption (85%): Strongest case, payback 3.1 years and surplus ZAR 243 million. Operational measures (load shifting, refrigeration scheduling) materially improve the economics.
- S5 — combined stress: Payback 6.4 years and surplus ZAR 106 million. Survives, but margin is thin; mitigation should target at least one of the four levers before award.
6. Mini certification block
- Design basis: CSIR PV Green Card 2024 (P50, fixed-tilt 20–28°, linear 0.5%/yr degradation).
- Tariff basis: Eskom Tariff & Charge Book 2024/25, Schedule of Standard Prices, blended TOU + demand.
- Cost basis: tradevolt brief 2025-Q4, all-in EPC + grid interconnection, ZAR 9,500/kWp reference.
- Editorial review: muse-ba (pending).
7. HS code block — for reference only, duty rates PENDING
| HS code (6-digit) | Description (WCO 2022) | Duty rate — South Africa |
|---|---|---|
| 8541.43 | Photovoltaic cells, assembled in modules or made up into panels | PENDING |
| 8541.40 | Photosensitive semiconductor devices (incl. PV cells, not assembled) | PENDING |
| 8504.40 | Static converters (PV inverters) | PENDING |
| 7308.20 | Structures of iron/steel — towers and lattice masts, mounting frames | PENDING |
Lookup instructions: Confirm the applicable 8/10-digit tariff and MFN/preferential rate on the South African Revenue Service (SARS) TAR browser at www.sars.gov.za → "Customs & Excise" → "Tariff". Always verify against the latest SARS schedule and any applicable AfCFTA, SADC, or EU EPA preference before import. Duty rates on this page are intentionally marked PENDING and must not be asserted as fact.
Disclaimer: This review is editorial analysis by tradvolt.com. It is not a vendor quote, not a customs ruling, and not financial advice. All numbers derive from the named inputs above; substitute any input to refresh the calculation. Verification of HS classification, origin, and applicable duty is the responsibility of the importer.
8. Call to action
(1) Request a tailored RFQ: Request RFQ — 4 MWp cargo port solar, South Africa.
(2) Download the datasheet brief: Download datasheet (PDF) — cargo port solar 4 MWp, ZA.