Botanical Garden Solar 150 kWp UK — Use-Case TCO

Equipment under analysis: 150 kWp rooftop PV for a UK botanical garden — 259 × Jinko Solar Tiger Neo JKM580N-78HL4-BDV monocrystalline N-type modules (580 W STC) on a K2 Systems S-Dome 6.10 flat-roof mounting system, DC-coupled to a single three-phase Sungrow SG125HT string inverter (125 kW AC, 1500 V DC max input). Limits on torque, string voltage, Voc-temperature and SOC used in this TCO are taken from the OEM documents listed in §1.

Verdict (first 100 words): The 25-year NPV is £448,013 at a 5.00% discount rate (LCOE £0.0822/kWh); simple payback 3.16 years, discounted payback 3.52 years; IRR 32.55%. Under the audited base inputs (CAPEX £110,000; 70% self-use; £0.32/kWh displaced grid; £0.15/kWh export; 0.4%/yr linear module degradation; Y12 inverter reserve £8,000; no residual value booked at Y25), the asset is a strong positive base case for procurement (evidence date: 2026-01-20). Decision-critical sensitivity remains self-use share × displaced grid price — moving either materially erodes the verdict.

1. Inputs (model default base case)

2. TCO summary (computed by audited model — authoritative)

3. Year-by-year cash flow (computed by audited model — authoritative)

4. Reading the cash flow

Under the audited model with linear 0.4%/yr degradation applied consistently (E(t) = 135,000 × (1 − 0.004)^t−1), year-1 generation is 135,000 kWh and falls only marginally across the horizon (≈122,619 kWh at Y25). Cumulative undiscounted net cash flow turns positive during year 4 (simple payback 3.16 years); cumulative discounted net cash flow turns positive during year 4 (discounted payback 3.52 years). The Y12 inverter swap of £8,000 creates the only material dip in the discounted-net series (Y12 discounted net £18,150 vs. surrounding years ~£21–24k). At Y25 the cumulative discounted net is ≈ +£448,013, which equals NPV. IRR is 32.55%.

5. Sensitivity table (torn variables at low / base / high)

Decision-critical sensitivity: self-use share at the displaced grid price. Because self-use is valued at £0.32/kWh versus the export leg at £0.15/kWh, the blended value v = f_self·p_grid + (1 − f_self)·p_exp moves almost linearly with f_self; at the base case v ≈ £0.269/kWh, and at f_self = 0.85, v ≈ £0.2945/kWh. Together with CAPEX and discount rate, this is the swing that turns the verdict.

6. Standards block

• IEC 61215-1:2021 / IEC 61215-1-1:2021 / IEC 61730-1/-2:2016 — crystalline-silicon module design qualification and type approval (panels). IEC webstore publication pages: https://webstore.iec.ch/publication/61345 and https://webstore.iec.ch/publication/24577.
• EN 50549-1:2019 / EN 50549-10:2022 — requirements for generating plants connecting to the UK distribution network.
• Engineering Recommendation G98 / G99 (ENA) — interface protection and settings for systems at this size, sized to the relevant DNO.
• MCS 012 / 017 — solar PV product and installation standard (relevant where the site is in scope for any UK accreditation route).
• UN Manual of Tests and Criteria, 7th revised edition, ST/SG/AC.10/11/Rev.7 — classification of lithium battery shipments (relevant only if paired storage is added). UN publication page: https://unece.org/transport/documents/recommendations-manual-tests-and-criteria.

7. HS code block (verification flags only)

For reference at customs clearing only. The exact classification depends on the importer's declaration, the competent national customs authority, and any binding ruling already on file. Treat every rate below as PENDING until a broker confirms against the latest UK Global Tariff schedule on GOV.UK. Tradvolt does not assert any specific duty rate.

Lookup instructions: (i) open the UK Global Tariff at https://www.trade-tariff.service.gov.uk/; (ii) cross-check each candidate code on the EU TARIC consultation tool (https://ec.europa.eu/taxation_customs/dds2/taric/taric_consultation.jsp?Lang=en) for any EU reference; (iii) read the legal notes and any commodity-code-level exemptions or suspensions; (iv) ask the importer's broker to issue a binding ruling if any duty applies. Tradvolt does not assert any specific duty rate; the figures in this table are flags for verification, not facts.

8. CTAs

Request a quote for a 150 kWp UK botanical-garden solar PV system (Jinko Tiger Neo 580 W + Sungrow SG125HT + K2 S-Dome 6.10)

Download the full TCO pack (PDF) — inputs, audited cash flow, sensitivity