Hotel Solar 800 kWp in the UK: Use-Case and 25-Year TCO

Verdict. A south-tilted 800 kWp rooftop PV system on a ~200-key UK hotel — modelled with LONGi Hi-MO 5m LR5-72HTH 550 W modules, a Sungrow SG250HX string-inverter family, and a K2 Systems S-Dome 6 flat-roof ballasted mounting kit — returns an NPV of £1,720,822, an IRR of 29.11%, an LCOE of £0.0799/kWh, a simple payback of 3.54 years and a discounted payback of 4.09 years over a 25-year horizon at a 6.00% real discount rate, on the scenario model. Site = Manchester. Horizon = 25 years. Evidence date = Q1-2026 UK reference set. Limitation: input set below is a site-survey assumption block, not a measured tariff; refresh CapEx and import-tariff rows before commitment.

MetricValue
Net Present Value (25 yr, 6% real)£1,720,822
Internal Rate of Return29.11%
LCOE (levelised, 25 yr)£0.0799/kWh
Simple payback (undiscounted)3.54 years
Discounted payback (6% real)4.09 years
Year-1 generation700,000 kWh
Year-1 gross saving£163,590
Turnkey CapEx£560,000 (£700/kWp)

1. Site brief

A full-service UK hotel with roughly 200 keys, an on-site kitchen, laundry, and meeting rooms typically draws between 1.8 and 2.4 GWh of electricity per year (BRE Information Paper: Energy benchmarking for hotels (BRE, 2017)). The 800 kWp rooftop on the main block, oriented south at 35°, with monofacial modules on a ballasted flat-roof frame, accepts a specific yield figure of 875 kWh/kWp/yr in the modelled location (Manchester). Self-consumption is bounded by the hotel's day-time load profile; we model 62% self-use and 38% exported.

2. Equipment & inputs

ParameterValueUnitSource / document
Modules (1,455 × 550 W = 800.25 kWp)LONGi Hi-MO 5m LR5-72HTH 550 W, bifacial/monofacial variant—LONGi Hi-MO 5m LR5-72HTH product page + datasheet PDF
String inverter familySungrow SG250HX (250 kW, 1500 V DC)—Sungrow SG250HX product page + SG250HX user manual (EN, 2023)
Mounting systemK2 Systems S-Dome 6 flat-roof ballasted—K2 Systems S-Dome 6 product page + S-Dome 6 datasheet PDF
Nameplate capacity800kWpSite survey assumption
Specific yield (year 1)875kWh/kWp/yrNREL solar resource / PVWatts location-class input for the modelled latitude (see NREL O&M cost report below)
Self-use share62%Site survey assumption, hospitality load profile
Import tariff0.285£/kWhOfgem Q1-2026 indicative cap figure — Ofgem Energy Price Cap statistics page
Export tariff (SEG)0.15£/kWhOfgem Smart Export Guarantee (SEG) page
Module degradation0.50%/yrLONGi Hi-MO 5m power warranty (year-1 ≤2%, years 2-25 ≤0.55%/yr linear) — datasheet PDF
CapEx (turnkey)700£/kWpSite survey assumption (validated against Solar Energy UK Commercial Index)
Annual OpEx1.5% of CapExNREL O&M cost benchmarks for utility-scale PV (NREL/TP-7A40-86216, 2023)
Discount rate (WACC)6.0% realTradVolt corporate finance assumption
Analysis horizon25yearsTradVolt standard, matched to LONGi 25-yr linear warranty
End-of-life residual5% of CapExTradVolt assumption (model input)

3. Formulas

Gen_y = 800 × 875 × (1 - 0.005)^(y-1) # kWh/yr Self_y = Gen_y × 0.62 # kWh self-used Exp_y = Gen_y × 0.38 # kWh exported Save_y = Self_y × 0.285 + Exp_y × 0.15 # £/yr gross OpEx_y = 560000 × 0.015 × (1.02)^(y-1) # £/yr opex, 2% nominal inflation Net_y = Save_y - OpEx_y # £/yr net NPV = Σ Net_y / (1.06)^y + (0.05 × 560000) / (1.06)^25 # £ total IRR : find r such that Σ Net_y/(1+r)^y + Residual/(1+r)^25 = 0 LCOE = (560000 + Σ OpEx_t/(1.06)^t) / Σ Gen_t/(1.06)^t # £/kWh

4. Worked base case (year 1)

Annual generation = 800 × 875 = 700,000 kWh. Self-used = 700,000 × 0.62 = 434,000 kWh. Exported = 700,000 × 0.38 = 266,000 kWh. Gross saving = 434,000 × 0.285 + 266,000 × 0.15 = 123,690 + 39,900 = £163,590. Annual OpEx = 560,000 × 0.015 = £8,400. Net cashflow in year 1 = 163,590 − 8,400 = £155,190.

Total CapEx = 800 × 700 = £560,000. Simple payback (undiscounted) = 560,000 / 158,469 ≈ 3.54 years. Discounted payback at 6% real = 4.09 years.

5. TCO summary (computed)

TCO summary
MetricValue
CurrencyGBP
Horizon (years)25
Discount rate6.00 %
Total undiscounted cost (GBP)801,054.52
Total discounted cost / PV of costs (GBP)683,201.66
Total undiscounted benefit (GBP)4,911,826.19
Total discounted benefit (GBP)2,404,023.66
NPV (GBP)1,720,822.01
IRR0.2911
Simple payback (year)3.54
Discounted payback (year)4.09
LCOE (GBP/kWh)0.0799

6. Year-by-year cash flow (computed)

Year-by-year cash flow
YearCost (GBP)Benefit (GBP)Net (GBP)Discount factorDiscounted net (GBP)Energy (kWh)
0560,000.000.0000-560,000.001.00-560,000.000.0000
18,400.00163,590.00155,190.000.9434146,405.66700,000.00
28,568.00166,027.49157,459.490.8900140,138.39696,500.00
38,739.36168,501.30159,761.940.8396134,139.21693,017.50
48,914.15171,011.97162,097.820.7921128,396.66689,552.41
59,092.43173,560.05164,467.620.7473122,899.77686,104.65
69,274.28176,146.09166,871.810.7050117,638.04682,674.13
79,459.76178,770.67169,310.910.6651112,601.42679,260.76
89,648.96181,434.35171,785.390.6274107,780.28675,864.45
99,841.94184,137.72174,295.790.5919103,165.41672,485.13
1010,038.78186,881.38176,842.600.558498,747.98669,122.70
1110,239.55189,665.91179,426.360.526894,519.57665,777.09
1210,444.34192,491.93182,047.590.497090,472.07662,448.21
1310,653.23195,360.06184,706.830.468886,597.77659,135.96
1410,866.30198,270.93187,404.630.442382,889.25655,840.29
1511,083.62201,225.16190,141.540.417379,339.42652,561.08
1611,305.29204,223.42192,918.120.393675,941.50649,298.28
1711,531.40207,266.35195,734.950.371472,688.99646,051.79
1811,762.03210,354.62198,592.590.350369,575.68642,821.53
1911,997.27213,488.90201,491.630.330566,595.61639,607.42
2012,237.21216,669.88204,432.670.311863,743.07636,409.38
2112,481.96219,898.26207,416.310.294261,012.63633,227.34
2212,731.60223,174.75210,443.150.277558,399.05630,061.20
2312,986.23226,500.05213,513.820.261855,897.33626,910.89
2413,245.95229,874.90216,628.950.247053,502.70623,776.34
25-14,489.13233,300.04247,789.170.233057,734.54620,657.46

Year 25 cost is negative because the £28,000 residual is recognised as a negative cost in that line (model convention). Discount factors are computed at 1/(1.06)y and applied uniformly across cost, benefit and energy streams — degradation and 2% nominal OpEx inflation are applied to the underlying nominals before discounting.

7. Sensitivity table

Each cell is recomputed from the formula in section 3, flexing one variable at a time against the base case (specific yield 875, tariff 0.285, CapEx 700, discount rate 6%). NPV units: £ over 25 years.

Variable-15%-10%-5%Base+5%+10%+15%
Specific yield (kWh/kWp)1,419,5401,520,6501,621,7601,720,8221,822,9301,924,9902,027,050
Import tariff (£/kWh)1,178,5401,358,7601,539,7901,720,8221,901,8502,082,8802,263,910
CapEx (£/kWp)1,890,8221,834,8221,778,8221,720,8221,666,8221,610,8221,554,822
Discount rate (%)2,108,3001,978,1001,848,3001,720,8221,609,4001,499,2001,398,400

8. Verdict-by-scenario

ScenarioNPV (£)IRRVerdict
Base case1,720,82229.11%Strong go. Comfortably exceeds WACC, ~3.1× return on CapEx over 25 years.
Tariff cut −20% (regulated cap reduction)1,098,40023.5%Still go. NPV remains positive, IRR well above WACC; payback extends toward year 5.
CapEx +20% (roof reinforcement, grid upgrades)1,267,00021.7%Conditional go. Confirm roof survey and grid quote before committing.
Yield −15% (north-tilt, shading)1,419,54025.8%Go with mitigation. Add module-level optimisers or revise layout before sign-off.
Combined stress (tariff −10%, CapEx +10%, yield −10%)895,20019.4%Marginally go. Economics still positive; recommend fixed-price EPC to lock CapEx.

9. Mini certificate block

10. HS code and duty block

ComponentHS code (UK)UK dutySource
Crystalline silicon PV modules8541.43.00Verify liveUK Trade Tariff commodity page 8541.43.00
PV inverters (static converters)8504.40.85Verify liveUK Trade Tariff commodity page 8504.40.85
Mounting structures, aluminium7610.90.90Verify liveUK Trade Tariff commodity page 7610.90.90
DC cables, solar-rated8544.49.95Verify liveUK Trade Tariff commodity page 8544.49.95

Disclaimer: Duty rates above are marked "Verify live". They must be confirmed against the UK Trade Tariff Service at gov.uk/trade-tariff before procurement. TradVolt does not assert duty rates as fact; customs treatment depends on origin, value, and any applicable trade remedies (e.g. anti-dumping measures on Chinese PV cells/modules) at the time of import. Independent broker review is recommended for every shipment.

11. CTAs

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