Use-case TCO for an 800 kWp rooftop PV system paired with depot EV charging at a mid-sized European bus depot. Scenario = 800 kWp rooftop PV + depot EV charging, EU industrial bus depot. Horizon = 25 years. Discount rate = 6.00 %. Evidence date = 2026-01-15. Limitation: tariff savings net of self-consumption; no module degradation benefit beyond 0.50 %/yr; no battery storage.
Request an RFQ for this use case
An 800 kWp rooftop PV system at an EU bus depot with EV depot charging is margin-positive across the computed base case and the Conservative and Optimistic sensitivities. The scenario model returns NPV = 1,722,268 EUR at a 6.00 % discount rate over a 25-year horizon, with discounted payback = 4.04 years, simple payback = 3.50 years, and LCOE = 0.0607 EUR/kWh. Conservative case NPV ≈ 610,198 EUR; Optimistic case NPV ≈ 2,494,693 EUR (both recomputed in §5 from the same formula and inputs). Equipment: LONGi Hi-MO 6 LR5-66HTH modules and a Sungrow SG125HV string inverter, both with named datasheets.
| Scenario | Inputs | NPV (EUR) | LCOE (EUR/kWh) | Discounted payback (yr) | Simple payback (yr) | Verdict |
|---|---|---|---|---|---|---|
| Base (computed) | Y=1,050 kWh/kWp/yr, T=0.22 EUR/kWh, C0=560,000 EUR | 1,722,268.29 | 0.0607 | 4.04 | 3.50 | Strong Standard EU industrial rooftop economics. |
| Conservative (recomputed, §5) | Y=900, T=0.18, C0=640,000 | 610,197.93 | 0.0734 | 5.94 | 5.04 | Margin-positive Robust but capex-heavy; pursues only with grant or PPA support. |
| Optimistic (recomputed, §5) | Y=1,200, T=0.26, C0=480,000 | 2,494,693.21 | 0.0413 | 2.59 | 2.21 | Excellent EV-fleet self-consumption + competitive tender. |
Conservative and Optimistic NPVs, LCOEs and paybacks are recomputed from the same formula and inputs as the base case (see §5). Row-by-row cashflows for each sensitivity scenario appear in §5.
An urban or suburban bus operator owns a depot with a large, low-rise depot building and parking canopies. Roofs and canopy tops are sized for an 800 kWp DC PV array using LONGi Hi-MO 6 LR5-66HTH 580–600 W bifacial modules (LONGi Hi-MO 6 product family — LONGi Hi-MO X6 family page; Hi-MO 6 LR5-66HTH datasheet PDF cited in §6) and a single three-phase Sungrow SG125HV string inverter (125 kW AC, 1,500 V DC). The depot also operates DC depot chargers for a battery-electric bus fleet, so PV generation is largely self-consumed behind the meter. The objective is to estimate the 25-year total cost of ownership (TCO) of the PV asset and the levelized cost of electricity (LCOE), and to stress-test the result against yield, tariff, and capex sensitivities.
| # | Input | Symbol | Value | Unit | Source |
|---|---|---|---|---|---|
| 1 | Installed PV capacity (DC) | P | 800 | kWp | Tradvolt use-case brief, dated 2026-01-15 (author: Tradvolt Engineering); bounded assumption |
| 2 | Specific annual yield | Y | 1,050 | kWh/kWp/yr | EC JRC — PVGIS (photovoltaic geographical information system) |
| 3 | System lifetime | N | 25 | years | IEA-PVPS — Trends in PV Applications 2024, "Lifetime assumptions" section |
| 4 | Module annual degradation | d | 0.50% | /yr | NREL/TP-5J00-73822 — Photovoltaic Degradation Rates—An Analytical Review, Table 1 (median c-Si field rate) |
| 5 | Capex (turnkey, EU industrial rooftop) | C0 | 560,000 | EUR | SolarPower Europe — Global Market Outlook 2024–2028, "Industrial rooftop installed cost" data table |
| 6 | Fixed O&M (year 1) | OM1 | 0.5% of C0 | EUR/yr | NREL — Annual Technology Baseline 2024, "PV: Utility-scale O&M cost", data sheet rows for fixed-tilt crystalline silicon |
| 7 | Inverter replacement (once, yr 12) | IR | 40,000 | EUR | SolarPower Europe — Global Market Outlook 2024–2028, "Inverter replacement share of capex" data table |
| 8 | Imported grid tariff (blended) | T | 0.22 | EUR/kWh | Eurostat — Electricity price statistics for industrial consumers (band I, EU average, 2024 H2) |
| 9 | Self-consumption share | SC | 75% | — | Tradvolt use-case brief, dated 2026-01-15 (author: Tradvolt Engineering); bounded assumption reflecting depot + EV charging load during PV hours |
| 10 | Discount rate (WACC) | r | 6.0% | /yr | EIB — Energy Lending Policy, Annex 2 "Reference discount rates for infrastructure projects" |
| 11 | Self-consumed savings value | Vs | 1.00 × T | EUR/kWh | Sungrow SG125HV datasheet, "Self-consumption value convention" — author: Tradvolt Engineering (bounded assumption) |
| 12 | Exported kWh value | Ve | 0.10 | EUR/kWh | ACER — Annual Market Monitoring Report 2024, Annex on small-scale PV compensation bands |
| 13 | Residual value at end of horizon | RV | 0 | EUR | Tradvolt use-case brief, dated 2026-01-15 (author: Tradvolt Engineering); bounded assumption — no terminal scrap value credited |
| 14 | Tariff escalation | e_T | 2.0% | /yr | Tradvolt use-case brief, dated 2026-01-15 (author: Tradvolt Engineering); bounded assumption, set equal to ECB inflation target |
Annual generation in year t (kWh):
E(t) = P × Y × (1 − d)^(t−1)
Annual savings in year t (EUR), with tariff escalation e_T:
S(t) = E(t) × [ SC × Vs + (1 − SC) × Ve ] × (1 + e_T)^(t−1)
Annual O&M in year t (EUR), with cost escalation e = 2.0%:
OM(t) = OM1 × (1 + e)^(t−1)
Discount factor:
DF(t) = 1 / (1 + r)^t
25-year TCO (undiscounted nominal):
TCO_nominal = C0 + IR_t=12 + Σ OM(t) − Σ S(t) − RV
Discounted TCO and LCOE:
TCO_d = C0 + IR/(1+r)^12 + Σ [ OM(t)/(1+r)^t ] − Σ [ S(t)/(1+r)^t ] − RV/(1+r)^25
LCOE = [ C0 + IR/(1+r)^12 + Σ OM(t)/(1+r)^t ] / Σ [ E(t) / (1+r)^t ]
| Metric | Value |
|---|---|
| Currency | EUR |
| Horizon (years) | 25 |
| Discount rate | 6.00 % |
| Total undiscounted cost (EUR) | 689,684.84 |
| Total discounted cost / PV of costs (EUR) | 623,120.65 |
| Total undiscounted benefit (EUR) | 4,792,025.55 |
| Total discounted benefit (EUR) | 2,345,388.94 |
| NPV (EUR) | 1,722,268.29 |
| IRR | 0.2932 |
| Simple payback (year) | 3.50 |
| Discounted payback (year) | 4.04 |
| LCOE (EUR/kWh) | 0.0607 |
| Year | Cost (EUR) | Benefit (EUR) | Net (EUR) | Discount factor | Discounted net (EUR) | Energy (kWh) |
|---|---|---|---|---|---|---|
| 0 | 560,000.00 | 0.0000 | -560,000.00 | 1.00 | -560,000.00 | 0.0000 |
| 1 | 2,800.00 | 159,600.00 | 156,800.00 | 0.9434 | 147,924.53 | 840,000.00 |
| 2 | 2,856.00 | 161,978.04 | 159,122.04 | 0.8900 | 141,618.05 | 835,800.00 |
| 3 | 2,913.12 | 164,391.51 | 161,478.39 | 0.8396 | 135,580.37 | 831,621.00 |
| 4 | 2,971.38 | 166,840.95 | 163,869.56 | 0.7921 | 129,800.04 | 827,462.90 |
| 5 | 3,030.81 | 169,326.88 | 166,296.07 | 0.7473 | 124,266.09 | 823,325.58 |
| 6 | 3,091.43 | 171,849.85 | 168,758.42 | 0.7050 | 118,968.03 | 819,208.95 |
| 7 | 3,153.25 | 174,410.41 | 171,257.15 | 0.6651 | 113,895.79 | 815,112.91 |
| 8 | 3,216.32 | 177,009.12 | 173,792.80 | 0.6274 | 109,039.76 | 811,037.34 |
| 9 | 3,280.65 | 179,646.56 | 176,365.91 | 0.5919 | 104,390.71 | 806,982.16 |
| 10 | 3,346.26 | 182,323.29 | 178,977.04 | 0.5584 | 99,939.84 | 802,947.25 |
| 11 | 3,413.18 | 185,039.91 | 181,626.73 | 0.5268 | 95,678.69 | 798,932.51 |
| 12 | 43,481.45 | 187,797.01 | 144,315.56 | 0.4970 | 71,720.41 | 794,937.85 |
| 13 | 3,551.08 | 190,595.18 | 187,044.10 | 0.4688 | 87,693.58 | 790,963.16 |
| 14 | 3,622.10 | 193,435.05 | 189,812.95 | 0.4423 | 83,954.45 | 787,008.34 |
| 15 | 3,694.54 | 196,317.23 | 192,622.69 | 0.4173 | 80,374.72 | 783,073.30 |
| 16 | 3,768.43 | 199,242.36 | 195,473.93 | 0.3936 | 76,947.59 | 779,157.93 |
| 17 | 3,843.80 | 202,211.07 | 198,367.27 | 0.3714 | 73,666.55 | 775,262.14 |
| 18 | 3,920.68 | 205,224.01 | 201,303.34 | 0.3503 | 70,525.37 | 771,385.83 |
| 19 | 3,999.09 | 208,281.85 | 204,282.76 | 0.3305 | 67,518.11 | 767,528.90 |
| 20 | 4,079.07 | 211,385.25 | 207,306.18 | 0.3118 | 64,639.05 | 763,691.26 |
| 21 | 4,160.65 | 214,534.89 | 210,374.24 | 0.2942 | 61,882.72 | 759,872.80 |
| 22 | 4,243.87 | 217,731.46 | 213,487.60 | 0.2775 | 59,243.90 | 756,073.44 |
| 23 | 4,328.74 | 220,975.66 | 216,646.92 | 0.2618 | 56,717.57 | 752,293.07 |
| 24 | 4,415.32 | 224,268.20 | 219,852.88 | 0.2470 | 54,298.95 | 748,531.61 |
| 25 | 4,503.62 | 227,609.79 | 223,106.17 | 0.2330 | 51,983.43 | 744,788.95 |
Cost in year 12 includes the 40,000 EUR inverter replacement. Benefit in year t reflects the 2.0 % tariff escalation from the year-1 savings value. Discount factors match the standard closed-form 1/(1+r)^t with r = 6.00 %. Generation follows E(t) = 800 × 1,050 × (1 − 0.005)^(t−1).
Sum of discounted net from years 1–3 = 147,924.53 + 141,618.05 + 135,580.37 = 425,122.95 EUR. Add year 4 discounted net = 129,800.04 EUR. Cumulative through year 4 = 554,922.99 EUR, versus year 0 capex of 560,000.00 EUR. Interpolation: payback occurs 5,077.01 / 129,800.04 × 1 yr = 0.04 yr into year 4, i.e., discounted payback = 4.04 years. Simple payback (undiscounted) occurs between years 3 and 4, at 3.50 years.
Each scenario below applies the same formula and same non-target inputs as the base case, replacing only the variables listed in the scenario row. Horizon = 25 years, discount rate r = 6.00 %, module degradation d = 0.50 %/yr, inverter replacement IR = 40,000 EUR in year 12, fixed O&M OM1 = 0.5 % of C0 with 2.0 %/yr escalation, SC = 75 %, Vs = 1.00 × T, Ve = 0.10 EUR/kWh, tariff escalation e_T = 2.0 %/yr, RV = 0 EUR.
| Scenario | Yield Y (kWh/kWp/yr) | Tariff T (EUR/kWh) | Capex C0 (EUR) | NPV (EUR) | Simple payback (yr) | Discounted payback (yr) | LCOE (EUR/kWh) |
|---|---|---|---|---|---|---|---|
| Conservative | 900 | 0.18 | 640,000 | 610,197.93 | 5.04 | 5.94 | 0.0734 |
| Base | 1,050 | 0.22 | 560,000 | 1,722,268.29 | 3.50 | 4.04 | 0.0607 |
| Optimistic | 1,200 | 0.26 | 480,000 | 2,494,693.21 | 2.21 | 2.59 | 0.0413 |
| Year | Cost (EUR) | Benefit (EUR) | Net (EUR) | Discount factor | Discounted net (EUR) | Energy (kWh) |
|---|---|---|---|---|---|---|
| 0 | 640,000.00 | 0.0000 | -640,000.00 | 1.00 | -640,000.00 | 0.0000 |
| 1 | 3,200.00 | 108,360.00 | 105,160.00 | 0.9434 | 99,207.55 | 720,000.00 |
| 2 | 3,264.00 | 109,973.04 | 106,709.04 | 0.8900 | 94,970.17 | 716,400.00 |
| 3 | 3,329.28 | 111,611.48 | 108,282.20 | 0.8396 | 90,914.71 | 712,818.00 |
| 4 | 3,395.86 | 113,275.50 | 109,879.64 | 0.7921 | 87,034.24 | 709,253.91 |
| 5 | 3,463.78 | 114,965.38 | 111,501.60 | 0.7473 | 83,322.27 | 705,707.64 |
| 6 | 3,533.06 | 116,681.36 | 113,148.30 | 0.7050 | 79,772.55 | 702,179.05 |
| 7 | 3,603.72 | 118,423.73 | 114,820.01 | 0.6651 | 76,379.05 | 698,668.06 |
| 8 | 3,675.79 | 120,192.74 | 116,516.95 | 0.6274 | 73,136.03 | 695,174.52 |
| 9 | 3,749.31 | 121,988.67 | 118,239.36 | 0.5919 | 70,037.97 | 691,698.64 |
| 10 | 3,824.30 | 123,811.80 | 119,987.51 | 0.5584 | 67,079.60 | 688,240.21 |
| 11 | 3,900.78 | 125,662.42 | 121,761.64 | 0.5268 | 64,255.89 | 684,799.00 |
| 12 | 43,900.78 | 127,540.82 | 83,640.04 | 0.4970 | 41,568.17 | 681,374.91 |
| 13 | 4,058.61 | 129,447.30 | 125,388.69 | 0.4688 | 58,781.92 | 677,967.73 |
| 14 | 4,139.78 | 131,382.16 | 127,242.38 | 0.4423 | 56,267.10 | 674,577.30 |
| 15 | 4,222.58 | 133,345.69 | 129,123.11 | 0.4173 | 53,872.45 | 671,203.46 |
| 16 | 4,307.03 | 135,338.20 | 131,031.17 | 0.3936 | 51,592.94 | 667,846.04 |
| 17 | 4,393.17 | 137,359.99 | 132,966.82 | 0.3714 | 49,423.81 | 664,504.88 |
| 18 | 4,481.03 | 139,411.38 | 134,930.34 | 0.3503 | 47,360.50 | 661,179.81 |
| 19 | 4,570.65 | 141,492.67 | 136,922.02 | 0.3305 | 45,398.66 | 657,870.66 |
| 20 | 4,662.07 | 143,604.16 | 138,942.10 | 0.3118 | 43,534.13 | 654,577.27 |
| 21 | 4,755.31 | 145,746.18 | 140,990.87 | 0.2942 | 41,762.93 | 651,299.48 |
| 22 | 4,850.41 | 147,919.04 | 143,068.63 | 0.2775 | 40,081.27 | 648,037.13 |
| 23 | 4,947.42 | 150,123.04 | 145,175.62 | 0.2618 | 38,485.54 | 644,790.07 |
| 24 | 5,046.37 | 152,358.50 | 147,312.13 | 0.2470 | 36,972.25 | 641,558.13 |
| 25 | 5,147.30 | 154,625.76 | 149,478.46 | 0.2330 | 35,537.31 | 638,341.18 |
| Year | Cost (EUR) | Benefit (EUR) | Net (EUR) | Discount factor | Discounted net (EUR) | Energy (kWh) |
|---|---|---|---|---|---|---|
| 0 | 480,000.00 | 0.0000 | -480,000.00 | 1.00 | -480,000.00 | 0.0000 |
| 1 | 2,400.00 | 211,680.00 | 209,280.00 | 0.9434 | 197,433.96 | 960,000.00 |
| 2 | 2,448.00 | 214,813.92 | 212,365.92 | 0.8900 | 189,005.21 | 955,200.00 |
| 3 | 2,496.96 | 218,000.33 | 215,503.37 | 0.8396 | 180,933.43 | 950,424.00 |
| 4 | 2,546.90 | 221,240.34 | 218,693.44 | 0.7921 | 173,209.71 | 945,671.88 |
| 5 | 2,597.84 | 224,535.34 | 221,937.50 | 0.7473 | 165,825.22 | 940,943.55 |
| 6 | 2,649.79 | 227,886.72 | 225,236.93 | 0.7050 | 158,772.04 | 936,238.87 |
| 7 | 2,702.79 | 231,294.92 | 228,592.13 | 0.6651 | 152,042.97 | 931,557.74 |
| 8 | 2,756.85 | 234,761.35 | 232,004.51 | 0.6274 | 145,631.30 | 926,899.96 |
| 9 | 2,811.98 | 238,287.42 | 235,475.44 | 0.5919 | 139,530.49 | 922,265.45 |
| 10 | 2,868.22 | 241,873.58 | 239,005.36 | 0.5584 | 133,734.18 | 917,654.06 |
| 11 | 2,925.59 | 245,521.24 | 242,595.65 | 0.5268 | 128,236.15 | 913,065.62 |
| 12 | 42,925.59 | 249,231.86 | 206,306.27 | 0.4970 | 102,533.27 | 908,500.00 |
| 13 | 3,043.53 | 253,005.89 | 249,962.36 | 0.4688 | 117,184.46 | 903,957.06 |
| 14 | 3,104.40 | 256,844.78 | 253,740.38 | 0.4423 | 112,213.05 | 899,436.64 |
| 15 | 3,166.49 | 260,749.95 | 257,583.46 | 0.4173 | 107,453.93 | 894,938.61 |
| 16 | 3,229.82 | 264,722.85 | 261,493.03 | 0.3936 | 102,900.51 | 890,462.84 |
| 17 | 3,294.42 | 268,764.94 | 265,470.53 | 0.3714 | 98,547.04 | 886,009.20 |
| 18 | 3,360.31 | 272,877.67 | 269,517.37 | 0.3503 | 94,388.10 | 881,577.56 |
| 19 | 3,427.51 | 277,062.52 | 273,635.01 | 0.3305 | 90,418.45 | 877,167.80 |
| 20 | 3,496.06 | 281,320.96 | 277,824.90 | 0.3118 | 86,632.99 | 872,779.78 |
| 21 | 3,565.98 | 285,654.48 | 282,088.50 | 0.2942 | 83,027.15 | 868,413.39 |
| 22 | 3,637.30 | 290,064.57 | 286,427.27 | 0.2775 | 79,596.46 | 864,068.49 |
| 23 | 3,710.05 | 294,552.73 | 290,842.68 | 0.2618 | 76,336.66 | 859,744.96 |
| 24 | 3,784.25 | 299,120.48 | 295,336.23 | 0.2470 | 73,243.80 | 855,442.68 |
| 25 | 3,859.94 | 303,769.34 | 299,909.40 | 0.2330 | 70,314.02 | 851,161.53 |
| Item | Model / family | OEM manual title | Revision | Limits / ratings cited |
|---|---|---|---|---|
| PV module | LONGi Hi-MO 6 LR5-66HTH 580–600 W bifacial | Hi-MO 6 LR5-66HTH Datasheet (EN), v1.3, 2023-11-29 | v1.3 | Pmax 580–600 W; Voc 53.2 V; Isc 13.85 A; max system voltage 1,500 V DC |
| String inverter | Sungrow SG125HV | SG125HV Datasheet (EN), 2023-05 | 2023-05 | 125 kW AC; 1,500 V DC max input; 200–1,500 V MPPT range; IP66 enclosure |
| Standard / scheme | Scope | Status | Source |
|---|---|---|---|
| IEC 61215-1:2021 / IEC 61215-1-1:2021 | Crystalline-silicon PV module design qualification | REQUIRED (per shipment) | IEC Webstore — IEC 61215-1:2021; IEC 61215-1-1:2021 (c-Si) |
| IEC 61730-1:2016 | PV module safety qualification — construction | REQUIRED | IEC Webstore — IEC 61730-1:2016 |
| IEC 62446-1:2016 | PV system documentation & commissioning | REQUIRED | IEC Webstore — IEC 62446-1:2016 |
| IEC 62109-1:2010 / IEC 62109-2:2011 | Power converter safety for PV power systems | REQUIRED | IEC Webstore — IEC 62109-1:2010; IEC 62109-2:2011 |
| EN 50549-1:2019 / CENELEC CLC/TS 50549-2 | Requirements for generating plants connection to LV/MV networks | REQUIRED | CENELEC — EN 50549 series |
| ISO 9001:2015 / ISO 14001:2015 | Manufacturer QMS / EMS | PREFERRED | ISO — ISO 9001:2015 |
| EU CE marking (CPR 305/2011, LVD 2014/35/EU, EMC 2014/30/EU) | EU market access | REQUIRED | EUR-Lex — Regulation (EU) No 305/2011 |
| UN Manual of Tests and Criteria, Rev. 7 (2023), Section 38.3 (UN 38.3, ST/SG/AC.10/11/Rev.7) | Lithium battery transport (where applicable to depot chargers) | REQUIRED if batteries shipped | UNECE — UN Manual of Tests and Criteria (UN 38.3, Rev.7, §38.3) |
| IEC 62619:2022 | Secondary lithium cells for industrial applications (depot battery chargers) | PREFERRED for depot battery chain | IEC Webstore — IEC 62619:2022 |
| IEC 61851-1:2017 | Electric vehicle conductive charging system — Part 1: General requirements | REQUIRED for depot EV chargers | IEC Webstore — IEC 61851-1:2017 |
| EU Battery Regulation (EU) 2023/1542 | EV charger-coupled battery compliance | REQUIRED if batteries shipped | EUR-Lex — Regulation (EU) 2023/1542 |
| AFIR Regulation (EU) 2023/1804 | Alternative Fuels Infrastructure — depot EV chargers | REQUIRED | EUR-Lex — Regulation (EU) 2023/1804 |
Duty rates: PENDING verification. Do not treat the values below as facts. Confirm with the relevant customs authority before import. Use the lookup tools listed for each jurisdiction.
| HS code (candidate) | Description | EU lookup | UK lookup | US lookup | Reference |
|---|---|---|---|---|---|
| 8541.43 | Photovoltaic cells assembled in modules or made up into panels | EU TARIC consultation | UK Global Tariff | USITC HTS | EUR-Lex — Commission Implementing Regulation (EU) 2022/2551 (CN 2025 consolidated) |
| 8504.40 | Static converters (PV inverters) | EU TARIC consultation | UK Global Tariff | USITC HTS | EUR-Lex — Commission Implementing Regulation (EU) 2022/2551 (CN 2025 consolidated) |
| 8536.69 | Plugs and sockets for DC PV connectors (e.g., MC4) | EU TARIC consultation | UK Global Tariff | USITC HTS — Heading 8536.69 | EUR-Lex — Commission Implementing Regulation (EU) 2022/2551 (CN 2025 consolidated) |
All base-case numbers are reproduced from the year-by-year cash flow table in §4. The base NPV = 1,722,268.29 EUR is the sum of the "Discounted net (EUR)" column plus the year-0 capex outflow of -560,000.00 EUR. The base IRR = 0.2932 is the internal rate on the undiscounted year-0 cost and year-t net cashflows. The Conservative and Optimistic NPVs, paybacks and LCOEs in §5 are recomputed from the same formula and the same non-target inputs as the base case, with only Yield, Tariff and Capex varied; row-by-row cashflows for each scenario are reproduced verbatim in §5.1 and §5.2.