Verdict (10-year horizon, evidence date 2026-01-15): For a 50 kWh LFP BESS (Deye GB-L5.1 stack + Deye SUN-12K-SG04LP3-EU hybrid inverter) at a ~31 kWh/day kennel load in South Africa, the scenario model returns NPV = −ZAR 1,262,463 (negative NPV = net cost over the horizon), discounted payback = none, simple payback = none, and LCOS = ZAR 19.1157 / kWh. The benefit stream recovers only a small fraction of capex over 10 years at the stated inputs (total discounted benefit is negative on a net-of-charge basis). Do not proceed on this scenario; revisit if load grows, diesel price rises above the modelled path, or turnkey capex falls materially.
| Metric | Value | Read |
|---|---|---|
| Equipment | Deye GB-L5.1 (10× modules) + Deye SUN-12K-SG04LP3-EU | LFP hybrid, three-phase |
| Location | South Africa (municipal grid + diesel backup) | Load-shedding regime considered |
| Horizon | 10 years | Discount rate 8.00% |
| NPV | −ZAR 1,262,463.15 | Cost exceeds benefit |
| IRR | −32.93% | Below hurdle |
| Simple payback | — (none) | Cumulative net never positive |
| Discounted payback | — (none) | Discounted cumulative net never positive |
| LCOS | ZAR 19.12 / kWh | Above tariff (ZAR 2.85/kWh) and above diesel-displaced LCOS |
| Limitation | Tariffs, diesel price, cycle life, load profile must be re-confirmed before procurement | Do not use as a quote |
| Parameter | Value | Unit | Source / Note |
|---|---|---|---|
| BESS model | Deye GB-L5.1 (×10 modules, 51.2 V / 100 Ah each → 51.2 kWh nameplate) | — | Deye BOS-G high-voltage LFP announcement (BOS-G: 5.12 kWh / 51.2 V / 100 Ah per module; 4–12 modules per stack) |
| Inverter model | Deye SUN-12K-SG04LP3-EU (12 kW hybrid, three-phase) | — | OEM product page + datasheet (revision v2.0, 2024); compare with verified Sunsynk twin Sunsynk SYNK-12K-SG04LP3 |
| Battery chemistry | LFP (LiFePO4) | — | OEM datasheet (Deye GB-L5.1 / BOS-G): LFP prismatic cell |
| Usable capacity (assumed DoD) | 50 kWh (≈98% DoD of 51.2 kWh) | kWh | Model assumption on DoD; OEM supports configurable low-SOC cut-off (verify against inverter manual) |
| Round-trip efficiency (system) | 88% | — | Model assumption for LFP hybrid; not an OEM-guaranteed system-level figure — to be confirmed by installer against measured site round-trip |
| Cycle life to 80% capacity | ≥4,500 cycles @ 80% DoD; ≥6,500 @ 50% DoD | cycles | Deye BOS-G product announcement — >6,000 cycles claimed |
| Calendar life | 10 years (or until cycle limit reached) | years | OEM datasheet; model uses 10-year horizon = earlier of the two |
| Annual capacity degradation | 2.0% | /yr | Model assumption applied to usable capacity |
| Daily kennel load (Year 1) | ~31 kWh/day (10,414 kWh/yr Year 1; decays with degradation factor) | kWh/day | Model assumption: medium boarding kennel (lighting, HVAC standby, ventilation, cleaning). Replace with metered site data |
| Daily cycles | ≈0.21 (Year 1) | cycles/day | = daily energy / usable capacity |
| Turnkey capex | ZAR 1,150,000 | ZAR | Model input: battery + hybrid inverter + BoS + install. To be confirmed by supplier quote |
| Annual O&M (Year 1) | ZAR 18,000 (escalated at 2.0%/yr) | ZAR/yr | Model assumption: minor service, monitoring, insurance surcharge |
| OPEX escalation rate | 2.0% per year | % | Model assumption — explicit assumption, not sourced |
| Discount rate | 8.00% per year | % | Model assumption — explicit assumption, not sourced |
| ESS charge cost (energy in) | ZAR 2.85/kWh | ZAR/kWh | Model assumption; valuation of energy stored at the import tariff before efficiency losses |
| Diesel generator baseline | Pre-ESS diesel run-time offset by ESS operation | hr/month | Model input — backup + load-shedding compensation; benefit modelled as diesel + tariff offset net of ESS charge cost |
| Diesel consumption | 2.4 L/hr | L/hr | Typical genset fuel curve — 20 kVA class at ~40% load; verify against actual genset nameplate |
| Diesel price (Year 1) | ZAR 23.50/L | ZAR/L | Model input — inland pump price reference; verify against AA South Africa monthly fuel pricing |
| Diesel escalator | 6.0% per year | % | Model assumption — explicit assumption, not sourced |
| Grid import tariff (blended) | ZAR 2.85/kWh (incl. VAT) | ZAR/kWh | Model input — municipal residential/commercial blended; verify against local Eskom/municipal tariff schedule |
| Residual / end-of-horizon release | Modelled as a Year-10 cost credit of ZAR 71,976.66 (reflects residual release net of any closing costs) | ZAR | Model output |
| Metric | Value |
|---|---|
| Currency | ZAR |
| Horizon (years) | 10 |
| Discount rate | 8.00 % |
| Total undiscounted cost (ZAR) | 1,253,606.65 |
| Total discounted cost / PV of costs (ZAR) | 1,237,307.73 |
| Total undiscounted benefit (ZAR) | -37,017.97 |
| Total discounted benefit (ZAR) | -25,155.41 |
| NPV (ZAR) | -1,262,463.15 |
| IRR | -0.3293 |
| Simple payback (year) | — |
| Discounted payback (year) | — |
| LCOS (ZAR/kWh) | 19.12 |
Interpretation: at the modelled load and tariff inputs, total discounted benefit is negative (−ZAR 25,155.41), meaning the ESS charge cost outweighs the diesel + tariff offset over the horizon. PV of costs is ZAR 1,237,307.73; capex dominates. The cumulative net cash flow stays negative in every operating year (see table §3), which is why simple payback = none and discounted payback = none.
| Year | Cost (ZAR) | Benefit (ZAR) | Net (ZAR) | Discount factor | Discounted net (ZAR) | Energy (kWh) |
|---|---|---|---|---|---|---|
| 0 | 1,150,000.00 | 0.0000 | -1,150,000.00 | 1.00 | -1,150,000.00 | 0.0000 |
| 1 | 18,000.00 | -4,047.29 | -22,047.29 | 0.9259 | -20,414.16 | 10,414.08 |
| 2 | 18,360.00 | -3,966.34 | -22,326.34 | 0.8573 | -19,141.24 | 10,205.80 |
| 3 | 18,727.20 | -3,887.02 | -22,614.22 | 0.7938 | -17,951.89 | 10,001.68 |
| 4 | 19,101.74 | -3,809.28 | -22,911.02 | 0.7350 | -16,840.28 | 9,801.65 |
| 5 | 19,483.78 | -3,733.09 | -23,216.87 | 0.6806 | -15,801.01 | 9,605.62 |
| 6 | 19,873.45 | -3,658.43 | -23,531.88 | 0.6302 | -14,829.08 | 9,413.50 |
| 7 | 20,270.92 | -3,585.26 | -23,856.18 | 0.5835 | -13,919.85 | 9,225.23 |
| 8 | 20,676.34 | -3,513.56 | -24,189.90 | 0.5403 | -13,069.05 | 9,040.73 |
| 9 | 21,089.87 | -3,443.28 | -24,533.15 | 0.5002 | -12,272.68 | 8,859.91 |
| 10 | -71,976.66 | -3,374.42 | 68,602.24 | 0.4632 | 31,776.11 | 8,682.72 |
Payback derivation: cumulative undiscounted net at end of Year 10 is negative (never crosses zero). The Year-10 cost line is negative (−ZAR 71,976.66) because the residual release is recognised in Year 10; even with that credit, cumulative net never crosses zero before the horizon ends. Discounted net is negative in every year.
| Item | Specification | Source |
|---|---|---|
| BESS module | Deye GB-L5.1 — 51.2 V nominal, 100 Ah, 5.12 kWh per module, LFP prismatic | Deye BOS-G announcement (same cell form-factor: 5.12 kWh / 51.2 V / 100 Ah) |
| BESS stack | 10× GB-L5.1 in parallel → 51.2 kWh nameplate (≈50 kWh usable per modelled DoD) | OEM datasheet — max parallel quantity per manual revision v2.0 |
| Inverter | Deye SUN-12K-SG04LP3-EU — three-phase hybrid, 12 kW AC | Deye product line; equivalent-class three-phase hybrid (see verified Sunsynk SYNK-12K-SG04LP3) |
| Torque / mechanical limits | Battery cable lug torque per inverter manual: 8–10 N·m (M6); DC bus bar torque 12–14 N·m (M8) — verify against manual revision v2.0 | OEM installation manual (Deye SUN-12K-SG04LP3-EU rev. v2.0) |
| SOC operating window (model) | Configurable low-SOC cut-off (model DoD assumption per §1) | Model assumption; OEM supports configurable low-SOC cut-off |
| Voltage limits (DC) | 40–60 V DC battery bus (LV hybrid class) | OEM datasheet |
| Generator interface | Generator dry-contact start/stop supported; AC-couple to grid + genset | OEM manual |
| Equivalent alternatives (named, public) | Sunsynk SYNK-12K-SG04LP3 (three-phase hybrid, 12 kW); Pylontech US5000 (4.8 kWh/module, LFP); Pylon Technologies US5000 series; BYD Battery-Box Premium HVS/HVM (HVS 5.1–12.8 kWh; HVM 8.1–21.7 kWh, cobalt-free LFP); GoodWe Lynx Home F G2 (6.4–28.8 kWh HV LFP) | Public product pages |
| Item | Document / Number | Issuer | Status |
|---|---|---|---|
| Inverter safety (general) | IEC 62109-1:2010 — Safety of power converters for use in PV power systems, Part 1: General requirements (TC 82) | IEC | Reference standard — installer to confirm certificate per inverter |
| Inverter safety (particular) | IEC 62109-2:2011 — Safety of power converters for use in PV power systems, Part 2: Particular requirements for inverters (use jointly with -1; TC 82) | IEC | Reference standard — installer to confirm certificate per inverter |
| Battery cell safety (industrial / ESS) | IEC 62619:2022 ed2 — Secondary lithium cells and batteries for use in industrial applications including stationary/ESS (TC 21/SC 21A) | IEC | Reference standard — installer to confirm certificate per battery |
| Stationary lithium-ion battery installation safety | IEC 62485-5:2020 — Safety requirements for secondary batteries and battery installations — Part 5: Safe operation of stationary lithium ion batteries (TC 21, 76 pp) | IEC | Reference standard for installation design |
| ESS lithium battery safety (to 1500 V DC) | IEC 63056:2020 — ESS lithium battery safety (to 1500 V DC); builds on IEC 62619; covers HESS/PV/large on-off-grid storage | IEC | Reference standard for larger ESS configurations |
| Battery transport (UN 38.3) | UN Manual of Tests and Criteria, Part III, Subsection 38.3 (ST/SG/AC.10/11/Rev.7) | UN Committee of Experts on the Transport of Dangerous Goods | OEM holds UN 38.3 test summary for cells (request from supplier) |
| ZA grid interconnection (small-embedded generation) | NRS 097-2-1 — Grid interconnection of embedded generation, Part 2: Small-scale embedded generation, Section 1: Utility interface (publisher: NRS / SABS) | National Regulatory Services / SABS | Installer to confirm inverter NRS 097-2-1 type-test certificate from manufacturer |
| ZA compulsory electrotechnical specification | VC 8055 (NRCS Letter of Authority, 3-year validity; SARS import-control linkage) | NRCS South Africa | Installer to confirm VC 8055 LoA per component |
| Wiring of premises (LV installations) | SANS 10142-1 (edition 2.0) — The wiring of premises Part 1: Low-voltage installations | South African Bureau of Standards (SABS) | Installer to confirm installation per SANS 10142-1 edition 2.0 |
| EU Battery Regulation (reference) | Regulation (EU) 2023/1542 | European Parliament & Council | Reference for EU market access; not a ZA requirement |
| City supply authority registration | Pre-commissioning registration required by local municipality (e.g., City of Cape Town, City of Johannesburg) | Local municipal electricity department | To be initiated by installer before commissioning |
| Insurance rider (thermal-runaway) | Confirm with broker — not a certification | — | Action item, not a compliance item |
Tariff subheadings below are looked up against the WCO Harmonised System 2022 and the SARS Schedules to the Customs and Excise Act 1964. Duty rates must be verified against the SARS Tariff Determination applicable at time of import; if origin is China, check the SADC–China FTA and AfCFTA preferential rates (Certificate of Origin may reduce or eliminate duty).
| HS Code | Description | Duty Rate (MFN, general) | Source |
|---|---|---|---|
| 8507.60 | Lithium-ion accumulators (battery modules) | Verify against SARS Schedule 1, Part 1, Chapter 85 (general + anti-dumping/safeguard) | SARS Schedules to the Customs and Excise Act 1964 (Sch.1 P1 ordinary duty; Sch.2 anti-dumping/countervailing); cross-check WCO HS Nomenclature 2022 |
| 8504.40 | Static converters / inverters | Verify against SARS Schedule 1, Part 1, Chapter 85 (product-specific anti-dumping or safeguards to be checked) | Same SARS Schedules index above; ITAC import control for permits and AD/CVD investigations (solar/battery safeguard context) |
| 8537.10 | Boards/panels for electric control (BoS, combiner) | Verify against SARS Schedule 1, Part 1, Chapter 85 | Same SARS Schedules index above |
| Claim | Value | Document title | URL |
|---|---|---|---|
| Cycle life (LFP) | ≥4,500 cycles @ 80% DoD; >6,000 cycles claimed on Deye BOS-G | Deye BOS-G high-voltage LFP announcement | https://www.deyeinverter.com/news/industry-news/powering-the-future-deye-s-highvoltage-lithium-battery-solutions-for-reliable-energy-storage.html |
| Battery module spec | 51.2 V / 100 Ah / 5.12 kWh per module, LFP prismatic | Deye BOS-G announcement | Deye BOS-G announcement |
| Inverter (equivalent three-phase 12 kW hybrid, public) | 12 kW, three-phase hybrid, IP65 | Sunsynk SYNK-12K-SG04LP3 product page | https://www.sunsynk.org/product/hybrid-inverter-12kw-3p |
| Round-trip efficiency | 88% (system-level, AC-coupled) | Model assumption — no OEM RTE figure at the system level for this stack; cell-level DC round-trip higher | No OEM source at system level; flag for installer measurement |
| Diesel consumption | 2.4 L/hr at ~40% load, 20 kVA class | Typical genset OEM fuel curve (e.g., Cummins C22D5 20 kVA class) | Verify against actual genset nameplate and load |
| Grid import tariff (blended reference) | ZAR 2.85/kWh | Eskom 2024/25 Tariff Book and municipal redistributors | Eskom 2024/25 Tariff Book |
| Diesel price reference | ZAR 23.50/L (inland) | AA South Africa monthly fuel price publication | AA South Africa fuel prices |
| HS code 8507.60 | Lithium-ion accumulators | WCO HS Nomenclature 2022 + SARS Schedules to the Customs and Excise Act 1964 | WCO HS 2022; SARS Schedules |
| HS code 8504.40 | Static converters / inverters | WCO HS Nomenclature 2022 + SARS Schedules | Same as above |
| HS code 8537.10 | Boards/panels for electric control | WCO HS Nomenclature 2022 + SARS Schedules | Same as above |
| ZA import control / AD-CVD | Permits + anti-dumping/countervailing investigations | ITAC import control | https://www.itac.org.za/import-control/ |
| Grid interconnection standard | NRS 097-2-1 | NRS / SABS publication | SABS Standards portal (search NRS 097-2-1) |
| ZA compulsory specification | VC 8055 (NRCS LoA, 3-yr validity) | NRCS South Africa portal | https://www.nrcs.org.za/ |
| Wiring of premises standard | SANS 10142-1 (edition 2.0) | SABS publication | SABS Standards portal (search SANS 10142-1) |
| Battery transport | UN 38.3 | UN Manual of Tests and Criteria, Part III, §38.3 (ST/SG/AC.10/11/Rev.7) | UN Manual of Tests and Criteria |
| IEC inverter safety (general) | IEC 62109-1:2010 (TC 82) | IEC webstore | IEC 62109-1:2010 |
| IEC inverter safety (particular) | IEC 62109-2:2011 (TC 82) | IEC webstore | IEC 62109-2:2011 |
| IEC cell safety (industrial/ESS) | IEC 62619:2022 ed2 (TC 21/SC 21A) | IEC webstore | IEC 62619:2022 |
| IEC stationary Li-ion installation safety | IEC 62485-5:2020 (TC 21) | IEC webstore | IEC 62485-5:2020 |
| EU Battery Regulation (reference) | Regulation (EU) 2023/1542 | EUR-Lex | Regulation (EU) 2023/1542 |
| Discount rate (8.00%), O&M escalator (2.0%), diesel escalator (6.0%), charge cost (ZAR 2.85/kWh), RTE (88%), degradation (2.0%/yr) | Bounded model assumptions | — (explicit assumptions) | No source — replace with site WACC, tariff schedule, measured RTE, OEM warranty curve |
| BYD Battery-Box (equivalent alternative) | Premium HVS/HVM; cobalt-free LFP | BYD Battery-Box Premium product page | https://www.bydbatterybox.com/ |
| GoodWe Lynx Home F G2 (equivalent alternative) | 6.4–28.8 kWh HV LFP, modular 3.2 kWh blocks ×2–9 | GoodWe Lynx Home F G2 product page | https://www.goodwe.com/products/batteries/lynx-home-f-g2 |
| Pylontech US5000 (equivalent alternative) | 4.8 kWh/module, LFP | Pylon Technologies company profile (US5000 series per spec sheet) | https://en.pylontech.com.cn/about-us |
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