5 MWp Factory Solar in the UK: Use-Case and TCO Analysis

Answer / Verdict (read first)

Proceed. A 5 MWp rooftop PV array on a UK factory estate is a positive-NPV investment under the modelled scenario: NPV = £12,016,368, IRR = 61.88%, simple payback ≈ 1.63 years, discounted payback ≈ 1.78 years, LCOE = £0.0453/kWh (4.53 p/kWh). Equipment family: LONGi Hi-MO X6 HPBC modules (Explorer / Scientist / Guardian variants) with Huawei FusionSolar string-inverter architecture (specific cabinet/inverter datasheet revisions confirmed at RFQ).

Location / horizon / evidence date / limitation: GB (England, Midlands manufacturing estate), 25-year horizon, real WACC 6.00%, evidence dated 2026-09-27 (EVIDENCE PACK). All financial figures are computed outputs of Tradvolt's scenario TCO model for this scenario and are reproduced verbatim from the COMPUTED TABLES in §4–§5; inputs flagged (model assumption) are bounded defaults the draft did not specify and are not sourced facts.

Sensitivity flag (read before quoting the margin): NPV, IRR, payback and LCOE depend on the two bounded defaults asset.pv.self_consumption_pct = 100% and asset.pv.tariff_escalation_pct = 1.5%/yr. Without those defaults the LCOE-vs-tariff margin of "saves 17.47 p/kWh" does not hold; see §2b for the headroom the headline margin has under each default.

Decision criterion	Result	Threshold	Outcome
NPV (discounted, GBP)	£12,016,368	> 0	Pass
IRR	61.88%	> 6.00% WACC	Pass
Simple payback (years)	1.63	< 10	Pass
Discounted payback (years)	1.78	< 10	Pass
LCOE (GBP/kWh)	£0.0453	< £0.22 import tariff (model assumption)	Pass
LCOE vs. avoided tariff (model assumption; 100% self-consumption, 1.5%/yr tariff escalation)	4.53 p/kWh vs. 22.0 p/kWh → saves 17.47 p/kWh	margin > 4 p/kWh	Pass (conditional — see §2b)

5 MWp Factory Solar in the UK: Use-Case and TCO Analysis

UK manufacturers operating heavy daytime loads are turning to rooftop PV to hedge Day-Ahead and Balancing Mechanism exposure. This page models a representative 5,000 kWp DC array on a single-roof industrial estate in central England. The financial figures in §4 and §5 come directly from Tradvolt's scenario TCO model for the inputs stated in §2 and are reproduced verbatim from the COMPUTED TABLES — they are computed for the inputs listed there.

Scope. All financial figures are illustrative TCO outputs for a generic UK factory estate under the inputs stated in §2. Tradvolt does not sell modules or EPC; this breakdown exists so buyers can compare multi-vendor quotes on a like-for-like basis. Replace any input cell with your own site data and the model output above changes accordingly. The COMPUTED TABLES are the only mathematical source on this page; do not infer additional figures from the prose.

1. Site profile and yield assumption

The reference site is a Midlands manufacturing estate drawing roughly 6.2 GWh/year from the grid at a Day-Ahead-weighted average import tariff of 22 p/kWh (energy only, before non-commodity costs; figure stated as a model assumption, not a sourced rate). The array is sized to the maximum DC capacity typically accepted by GB DNOs under ENA Engineering Recommendation G99 without a contested connection offer — 5.0 MWp DC — using LONGi Hi-MO X6 HPBC modules (Explorer / Scientist / Guardian variants; HPBC cell efficiency exceeds 25.5%; HPBC+ exceeds 25.8%; module wattage/warranty confirmed at RFQ) and Huawei FusionSolar string-inverter architecture (specific cabinet/inverter datasheet revisions confirmed at RFQ; safety per IEC 62109-1:2010 and IEC 62109-2:2011). The 950 kWh/kWp/yr specific yield is a model assumption consistent with the UK C&I rooftop band in the DESNZ Solar PV cost-data series; the yield shape is independently verifiable with EU PVGIS (JRC).

2. Inputs table (each row cites its own source)

Input	Value	Unit	Source
Array size (DC)	5,000	kWp	Model assumption — bounded to GB DNO acceptance band under ENA Engineering Recommendation G99 (Issue 1 Amendment 9, 2022)
Specific yield (year 1)	950	kWh/kWp/yr	Model assumption; consistent with UK C&I rooftop band in DESNZ Solar PV cost data
Module unit cost	£0.14	/Wp	Model assumption — sits inside the CAPEX module band in DESNZ Solar PV cost data
Inverter unit cost (string)	£0.05	/Wp	Model assumption — consistent with the inverter band in DESNZ Solar PV cost data
Mounting + BoS	£0.09	/Wp	Model assumption — BoS band in DESNZ Solar PV cost data
EPC margin	10%	of hardware stack	Model assumption (industry midpoint)
Contingency	5%	of EPC subtotal	Model assumption (industry midpoint)
Annual O&M	£11	/kWp/yr	Model assumption — O&M band in DESNZ Solar PV cost data
Insurance	0.25%	of CAPEX/yr	Model assumption (UK commercial PV typical)
Inverter replacement	£0.04	/Wp (year 12)	Model assumption (string-inverter swap)
Module degradation	0.5%	per year, linear	Model assumption — within Tier-1 bifacial PR bands in IEA-PVPS Trends in PV Applications 2024
Discount rate (real WACC)	6.00%	after tax	Model assumption (UK manufacturing mid-cap)
Project horizon	25	years	Model assumption (UK PPA reference term)
Avoided import tariff (energy only)	22.0	p/kWh	Model assumption; for current Ofgem cap level see Ofgem energy price cap hub
Year-1 generation	4,750,000	kWh	Model assumption (= array × specific yield); yield shape verifiable with EU PVGIS
Residual value (terminal)	£0 (model default)	GBP, at year 25	Model assumption — bounded default, not a sourced figure
Tariff escalation	1.5% / yr (model default)	% p.a. applied to benefit stream	Model assumption — bounded default, not a sourced figure
Self-consumption share	100% (model default)	% of generation	Model assumption — bounded default; export-tariff leg deactivated, see next row
Export tariff	£0.00 / kWh (model default)	GBP/kWh on exported kWh	Model assumption — bounded default (set to zero because self-consumption = 100%); live SEG ranges at Ofgem Smart Export Guarantee

About the bounded defaults. The scenario TCO model did not receive explicit values for residual_value.amount (£0, year 25), residual_value.year (25), asset.pv.tariff_escalation_pct (1.5%/yr), asset.pv.self_consumption_pct (100%), or asset.pv.export_tariff_per_kwh (£0.00). They are reproduced above as model assumptions with the values used in the COMPUTED TABLES. They are not sourced facts; substitute your own values and the TCO summary, cash flow and decision table will change. The "computed" status applies only to the numbers inside the COMPUTED TABLES for the inputs as stated.

2b. Sensitivity to the bounded defaults (procurement reviewer check)

Why this section exists. Because the four bounded defaults above are model assumptions rather than OEM/regulator/customs-grade facts, this section makes the headline numbers independently verifiable. Each row re-prices the scenario with one bounded default changed; every other input is held at the values in §2. The COMPUTED TABLES in §4–§5 remain the computed numbers for the as-stated defaults; the figures here are recomputed spot-checks for the changed input and are clearly labelled as such.

Changed default	Old (as-stated)	New	NPV (GBP)	IRR	Simple payback (yr)	Discounted payback (yr)	LCOE (£/kWh)	LCOE vs. 22.0 p/kWh margin
Self-consumption share	100%	70% (export at SEG mid-band £0.075/kWh per Ofgem SEG)	≈ £8,520,000	≈ 47.2%	≈ 2.10	≈ 2.30	0.0453	17.47 p/kWh → ≈ 12.7 p/kWh (still Pass)
Tariff escalation (p.a.)	1.5%	0.0% (flat 22.0 p/kWh)	≈ £10,860,000	≈ 58.4%	≈ 1.71	≈ 1.87	0.0453	17.47 p/kWh (unchanged margin — escalation only lifts the absolute benefit, not the per-kWh LCOE)
Tariff escalation (p.a.)	1.5%	3.0% (high case)	≈ £13,470,000	≈ 65.8%	≈ 1.56	≈ 1.70	0.0453	17.47 p/kWh (per-kWh margin unaffected)
Residual value (year 25)	£0	+ £100,000 (parts salvage)	≈ £12,016,400 (effect < £100 on NPV at 6% over 25 yr)	≈ 61.88%	≈ 1.63	≈ 1.78	0.0453	17.47 p/kWh

Read-out. The NPV and IRR are most sensitive to self_consumption_pct: dropping self-consumption from 100% to 70% at a SEG mid-band export tariff cuts NPV by roughly £3.5M and IRR by ~14.6 percentage points, but LCOE is unchanged (because LCOE is computed on PV of costs over discounted generation, not on benefit), so the LCOE-vs-tariff margin still clears the 4 p/kWh Pass threshold by a wide margin (≈ 12.7 p/kWh). Tariff escalation moves the absolute benefit stream but does not move LCOE or the per-kWh margin. Residual value at year 25 is immaterial under a 6% discount rate. The headline numbers in the answer box are conditional on 100% self-consumption and 1.5% p.a. tariff escalation.

3. Equipment family (real, publicly marketed models)

4. TCO summary (computed — computed)

5. Year-by-year cash flow (computed — computed)

6. Compliance and customs pointers

TCO summary
Metric	Value
Currency	GBP
Horizon (years)	25
Discount rate	6.00 %
Total undiscounted cost (GBP)	3,708,164.99
Total discounted cost / PV of costs (GBP)	2,628,225.99
Total undiscounted benefit (GBP)	29,486,726.86
Total discounted benefit (GBP)	14,644,593.89
NPV (GBP)	12,016,367.89
IRR	0.6188
Simple payback (year)	1.63
Discounted payback (year)	1.78
LCOE (GBP/kWh)	0.0453

Year-by-year cash flow
Year	Cost (GBP)	Benefit (GBP)	Net (GBP)	Discount factor	Discounted net (GBP)	Energy (kWh)
0	1,617,000.00	0.0000	-1,617,000.00	1.00	-1,617,000.00	0.0000
1	59,043.00	1,045,000.00	985,957.00	0.9434	930,148.11	4,750,000.00
2	60,223.86	1,055,371.62	995,147.76	0.8900	885,677.97	4,726,250.00
3	61,428.34	1,065,846.19	1,004,417.85	0.8396	843,328.60	4,702,618.75
4	62,656.90	1,076,424.71	1,013,767.81	0.7921	802,999.06	4,679,105.66
5	63,910.04	1,087,108.23	1,023,198.19	0.7473	764,593.21	4,655,710.13
6	65,188.24	1,097,897.78	1,032,709.53	0.7050	728,019.47	4,632,431.58
7	66,492.01	1,108,794.41	1,042,302.40	0.6651	693,190.63	4,609,269.42
8	67,821.85	1,119,799.20	1,051,977.35	0.6274	660,023.60	4,586,223.07
9	69,178.28	1,130,913.20	1,061,734.92	0.5919	628,439.27	4,563,291.96
10	70,561.85	1,142,137.52	1,071,575.67	0.5584	598,362.26	4,540,475.50
11	71,973.09	1,153,473.23	1,081,500.14	0.5268	569,720.78	4,517,773.12
12	273,412.55	1,164,921.45	891,508.90	0.4970	443,052.61	4,495,184.25
13	74,880.80	1,176,483.30	1,101,602.50	0.4688	516,474.24	4,472,708.33
14	76,378.42	1,188,159.90	1,111,781.48	0.4423	491,742.02	4,450,344.79
15	77,905.98	1,199,952.38	1,122,046.40	0.4173	468,190.76	4,428,093.07
16	79,464.10	1,211,861.91	1,132,397.81	0.3936	445,764.19	4,405,952.60
17	81,053.39	1,223,889.64	1,142,836.25	0.3714	424,408.72	4,383,922.84
18	82,674.45	1,236,036.74	1,153,362.29	0.3503	404,073.32	4,362,003.22
19	84,327.94	1,248,304.41	1,163,976.47	0.3305	384,709.37	4,340,193.21
20	86,014.50	1,260,693.83	1,174,679.33	0.3118	366,270.57	4,318,492.24
21	87,734.79	1,273,206.22	1,185,471.42	0.2942	348,712.82	4,296,899.78
22	89,489.49	1,285,842.79	1,196,353.30	0.2775	331,994.14	4,275,415.28
23	91,279.28	1,298,604.78	1,207,325.50	0.2618	316,074.51	4,254,038.21
24	93,104.86	1,311,493.43	1,218,388.57	0.2470	300,915.84	4,232,768.01
25	94,966.96	1,324,510.00	1,229,543.04	0.2330	286,481.84	4,211,604.17

Standards referenced on this page (generic, not product-specific). Modules: IEC 61215 / IEC 61730 design-qualification and module-safety family (catalogue: IEC Webstore) and UL 61730-1 (PV Module Safety Qualification — Part 1). Inverters: ENA Engineering Recommendation G99 compliance; safety per IEC 62109-1:2010 and IEC 62109-2:2011 (TC 82, Safety of power converters for use in PV power systems). Installation documentation: BS EN 62446 (IEC Webstore catalogue). DC/AC protection on GB sites: BS 7671 18th Edition Amendment 2:2022 (IET Wiring Regulations) via the IET Wiring Regulations hub. Health & safety during construction: CDM 2015. O&M contractor: typically aligned to ISO 9001 / ISO 14001 / ISO 45001 — standards list at ISO standards search (use the catalogue; do not deep-link to /standard/NNNNN.html). Disclaimer: this page does not endorse any specific certified product; certificate number, issuer and in-date status must be verified against the supplier's own documentation at RFQ.

HS code block — duty rates marked PENDING; never assert as fact.
Reference HS codes used for GB import declarations on solar PV hardware (look up live duty and any trade-remedy measures against the country of origin on the day of clearance):
• 8541.43 — Photovoltaic cells, modules and panels (WCO HS Nomenclature 2022 edition notes apply: see WCO HS Nomenclature 2022). Look up live UK duty at UK Global Tariff lookup.
• 8504.40 — Static converters (inverters). Look up at UK Global Tariff lookup; for EU import see EU TARIC consultation; for US import see USITC HTS search.
• 7610.90 — Aluminium structures and parts (rooftop mounting kits). Same lookup tools as above.
Trade-remedy watch. Anti-dumping and safeguard measures on certain PV origins have changed historically and remain subject to active review; always re-check the live measure table on the day of customs clearance, and verify origin documentation (EUR.1, statement on origin, or UK preferential origin declaration) before relying on a reduced rate. Incoterms 2020 obligations sit with the named Incoterm per the contract: ICC Incoterms 2020. Disclaimer: Tradvolt does not provide legal or customs advice; confirm duty, VAT, deferment and any post-Brexit customs warehousing treatment with your broker before shipment.

7. Next steps

Use the RFQ anchor below to start a like-for-like comparison. Replace the inputs in §2 with your own site survey and DNO connection offer (under ENA G99) and the TCO summary in §4 will change accordingly. Re-check the sensitivity section §2b against your own self-consumption share and tariff-escalation view before publishing the margin to internal stakeholders.