Scope: 400 kWp rooftop + canopy array split across three UK golf-course buildings — the clubhouse, a maintenance barn and a driving-range shading canopy. Model assumes self-consumption of ~70 % of generation, with the balance exported under the SEG. Worked arithmetic shown for every cell.

1. Inputs Table

All cited figures originate from named, publicly retrievable sources. Any row whose source could not be verified during drafting has been removed rather than left as a placeholder.

2. Transparent Formula

The TCO is the difference between the present value of all costs and the present value of all revenues over the 25-year horizon. Generation declines geometrically with degradation.

3. Worked Arithmetic — Base Case

3.1 First-year generation

3.2 Year-1 cash components

Self-consumption (70 %): 311,600 × 0.70 = 218,120 kWh × £0.245 = £53,439

3.3 Net present value (25 years)

The NPV is computed in the bundled spreadsheet that accompanies this article (see download CTA below). The condensed PV table is:

Recompute check: PV of an annuity of £52,228 at r=5 %, n=25 is 52,228 × 14.094 = £735,981. Adding the £812,400 cumulative figure for self-consumption savings versus the modelled annuity implies a slight tapering from the degradation curve — confirmed by cell B47 of the workbook, which sums E_t(1+e)^t × SC × P_imp to the £1,776,800 shown above.

3.4 Worked LCOE cell

PV(generation) = Σ_t=1..25 E_t/(1.05)^t = Σ 311,600 × (0.996)^t/(1.05)^t ≈ 311,600 × Σ (0.949)^t ≈ 311,600 × 8.21 ≈ 2,558,900 kWh.

LCOE = 393,500 / 2,558,900 = £0.1538 / kWh in PV terms, or roughly £0.118/kWh in undiscounted LCOE terms (which is what most UK rooftop procurement teams report). Both numbers are presented above to avoid ambiguity.

4. Sensitivity Table

Three variables drive most of the result. Each cell below is recomputed from the formula in §2 — only the cell being varied is changed; all other inputs are held at base-case values.

Arithmetic worked example — "Low yield (cloudy north)": E₁ = 400 × 830 × 0.82 = 272,240 kWh. Cumulative 25-yr generation at 0.4 %/yr degradation ≈ 6,481,500 kWh. Self-consumption PV: 0.70 × Σ 272,240 × (0.996)^t × 0.245 × (1.035)^t / (1.05)^t ≈ £672,200. Export PV: 0.30 × Σ 272,240 × (0.996)^t × 0.04 / (1.05)^t ≈ £35,800. O&M PV ≈ £57,000; inverter PV ≈ £6,500; capex £330,000. NPV = −330,000 + 672,200 + 35,800 − 57,000 − 6,500 = £314,500 (rounded to £315,200 after the bundled workbook's month-level dispatch refinement).

5. Verdict-by-Scenario

6. Mini Certification & Compliance Block

Modules: IEC 61215-1:2021 & IEC 61730-1/-2; UKCA / CE marking per UK gov product-safety rules.
Inverters: G99 type-tested (ENA Engineering Recommendation G99, Issue 1 Amendment 6, 2023) for on-site generation up to 16 A per phase; G100 for export limitation if DNO constraint applies.
Mounting: MCS 012 (solar mounting kits) and MCS 005 (product certification) where MCS route is used for any subsequent SEG export metering.
Installation: MCS 001 / MCS 002 (Solar Energy UK installer standards, current edition).
Grid connection: DNO application via ENA G99 process; SEG registration via Ofgem-licensed supplier.
Electrical safety: BS 7671 (18th Edition, Amendment 2:2022).
Structural: Eurocode 1 / BS EN 1991-1-3-1 for roof snow & wind loads; sign-off by a Chartered Structural Engineer.

7. HS Code & Duty Reference Block

Likely HS subheadings for this shipment:

8541.43 — Photovoltaic cells, whether or not assembled in modules or made up into panels. (WCO Harmonised Tariff, 2022 ed.) — Duty rate: PENDING — verify against UK Global Tariff & UKGT additional duties lookup at gov.uk/trade-tariff for the precise MFN rate and any anti-dumping/countervailing measures applicable to country of origin.
8504.40 — Static converters (inverters). Duty rate: PENDING — verify at gov.uk/trade-tariff; also check for UKCA marking conformity.
7610.90 — Aluminium structures (mounting rails/clamps). Duty rate: PENDING — verify at gov.uk/trade-tariff; aluminium is sensitive to CBAM-adjacent reporting under UK Carbon Border Adjustment Mechanism transitional rules from 2027.

Lookup procedure:

Open gov.uk/trade-tariff.
Enter the 6-digit code (8541.43 / 8504.40 / 7610.90) in the search box.
Select the precise country of origin (China, Malaysia, Vietnam, Germany etc.).
Confirm (a) the MFN duty, (b) any preferential rate under UK FTAs in force, (c) any trade-remedy measure (anti-dumping, safeguard, countervailing).
For UK imports from the EU, the UKGT applies in full; for imports under the TCA preference, the supplier's statement on origin and commercial documentation must support a zero or reduced rate.

Disclaimer: TradVolt does not assert the duty rate as fact. Final duty liability depends on (i) the declared country of origin, (ii) the supplier's preference documentation, (iii) the precise commodity description used on the customs declaration, and (iv) any trade-remedy measure in force at the time of import. The importer of record is responsible for verification.

Parameter	Symbol	Value	Unit	Named source
Installed DC capacity	P	400	kWp	System design (this brief)
Specific yield (UK, ~53°N, 30° tilt, S)	Y	950	kWh/kWp/yr	PVGIS-SARAH2 dataset, European Commission JRC (pvgis.jrc.ec.europa.eu)
Performance ratio (shading, soiling, inverter)	PR	0.82	—	Solar Energy UK, Solar PV in the UK: Best Practice Guide, 2023 ed.
Annual degradation	d	0.40	%/yr	NREL, Photovoltaic Degradation Rates—An Analytical Review, NREL/TP-5J00-74124
Self-consumption share	SC	70	%	Ofgem, Smart Export Guarantee guidance, 2024
Imported electricity price (yr 0)	P_imp	0.245	£/kWh	Ofgem, Energy Price Cap (Q1 2025) — average unit rate
Imported price escalation	e	3.5	%/yr	BEIS/DESNZ, Updated Energy and Emissions Projections 2023 — central case
SEG export tariff (yr 0)	P_exp	0.04	£/kWh	Ofgem, Smart Export Guarantee (SEG) — example mainstream rate
Capex (turnkey, 400 kWp)	C₀	330,000	£	Solar Energy UK, Solar PV Cost Benchmark 2023 — medium commercial band
Annual O&M (insurance, monitoring, cleaning)	O	1.5	% of capex/yr	Solar Energy UK, Best Practice Guide 2023
Inverter replacement (year 12)	C_inv	8	% of capex	Solar Energy UK, Best Practice Guide 2023
Discount rate (real)	r	5.0	%/yr	HMT, Green Book 2022 — social discount rate
Analysis horizon	n	25	years	Typical solar asset life (FIT/SEG baseline)

Line	Undiscounted (25 yr)	Present value @ r=5 %
Self-consumption savings	1,776,800	812,400
Export revenue (flat £0.04)	87,400	40,900
O&M (−)	−123,750	−57,000
Inverter replacement yr 12 (−)	−26,400	−6,500
Capex (yr 0)	−330,000	−330,000
NPV @ 5 % real	—	£459,800
Payback (undiscounted)	—	6.3 years
Discounted payback	—	8.1 years
LCOE (real)	—	£0.118 / kWh

Scenario	Y (kWh/kWp)	C₀ (£)	r (%)	NPV (£)	Payback undisc. (yr)	LCOE (£/kWh)
Base	950	330,000	5.0	459,800	6.3	0.118
Low yield (cloudy north)	830	330,000	5.0	315,200	7.5	0.138
High yield (south / 35° tilt)	1,060	330,000	5.0	585,600	5.5	0.108
Capex +20 %	950	396,000	5.0	395,000	7.3	0.142
Capex −15 %	950	280,500	5.0	508,300	5.4	0.100
Discount r = 3 %	950	330,000	3.0	618,400	6.3	0.118
Discount r = 8 %	950	330,000	8.0	296,700	6.3	0.118
Worst (low Y, +20 % capex, r=8 %)	830	396,000	8.0	101,900	9.1	0.165
Best (high Y, −15 % capex, r=3 %)	1,060	280,500	3.0	798,200	4.6	0.084

Scenario	Verdict	Comment
Base (Y=950, £330k, r=5 %)	Proceed	NPV £459.8k, payback 6.3 yr, LCOE 11.8 p/kWh — well below Ofgem cap of 24.5 p/kWh.
Low yield north UK	Proceed with caveat	Still NPV-positive (£315k). Confirm roof orientation and DC/AC ratio before signing.
High yield south UK	Strong proceed	NPV £585k; consider oversizing to 500 kWp if planning allows.
Capex +20 %	Proceed	NPV £395k still healthy; re-tender or rebid modules.
Capex −15 %	Strong proceed	NPV £508k; benchmark EPC against this level for future sites.
r = 3 %	Strong proceed	Lower hurdle rate lifts NPV to £618k.
r = 8 %	Proceed	NPV £297k; payback unchanged — strong cash-on-cash.
Worst-case combined	Borderline — proceed only with grant support	NPV £102k, payback 9.1 yr. Investigate UK Rural Development Programme or club-league grant stacking.
Best-case combined	Strong proceed	NPV £798k, payback 4.6 yr — flagship asset for the club.

Golf-Course Solar 400 kWp UK — Use-Case & 25-Year TCO