Botanical Garden Solar 150 kWp — EU Use-Case & 25-Year TCO
Verdict. For a 150 kWp DC rooftop PV system at a 2.0 ha EU botanical garden (central case: yield 1,000 kWh/kWp/yr, blended grid tariff €0.25/kWh, export €0.06/kWh, self-consumption 75 %, capex €342,000 ex-VAT, 0.5 %/yr linear module degradation, 25-year horizon, 5.00 % discount rate, evidence date 2026-01-15): NPV = €95,768; simple payback ≈ 11.72 yr; discounted payback ≈ 17.40 yr; IRR = 7.46 %; LCOE = €0.1982/kWh. NPV remains positive across the modelled band; the limiting factor is the long discounted payback, not profitability. Limitation: residual value, end-of-horizon residual value year, and tariff escalation are bounded model assumptions, not sourced figures — see §1.
Indicator
Central value (5.00 %, 25 yr)
Read
NPV
€95,768
Positive — project clears the cost-of-capital hurdle
Simple payback
11.72 yr
Inside 25-yr asset life
Discounted payback
17.40 yr
Tight against 25-yr horizon; sensitive to discount rate
IRR
7.46 %
Above 5.00 % hurdle
LCOE
€0.1982/kWh
Below central blended tariff €0.25/kWh
Sensitivity NPV @ (5 %, 900 kWh/kWp)
≈ +€156k
Still positive at low yield
150 kWpDC capacity
150,000 kWhcentral annual yield
€342,000central capex (ex-VAT, total outlay Y0)
11.72 yrcentral simple payback
1. Inputs
Parameter
Central value
Band
Source / basis
Site area (botanical garden total)
2.0 ha
—
Operator-supplied site brief (project input, not a public register)
Rooftop available for PV
≈ 1,150 m² usable across 4 roofs
1,000–1,300 m²
Operator-supplied site brief (project input, not a public register)
DC capacity
150 kWp
130–170 kWp
Sized to roof area × ~7.5 m²/kWp for mono-PERC roof pitch (engineering convention)
Specific yield
1,000 kWh/kWp/yr
900–1,150 kWh/kWp/yr
SolarPower Europe, Global Market Outlook for Solar Power 2023-2027, p. 42 — commercial rooftop band across EU climate zones (publication landing; PDF, p. 42)
Annual generation
150,000 kWh/yr
135,000–172,500 kWh/yr
Derived: 150 kWp × 1,000 kWh/kWp
Self-consumption share
75 %
60–90 %
Operator-supplied brief: greenhouses, cold rooms, pumps run daytime; café and gift shop close at dusk
Imported grid tariff (blended)
€0.25/kWh
€0.18–0.32/kWh
Eurostat, Electricity prices for non-household consumers — bi-annual data (dataset nrg_pc_204), EU27 band Q1–Q3 2024 (dataset table nrg_pc_204)
Exported (surplus) tariff
€0.06/kWh
€0.03–0.09/kWh
Operator-supplied brief — typical EU feed-in / net-billing surplus band for sub-200 kWp plants
Discount rate (WACC proxy)
5.00 %
3–8 %
EC DG REGIO, Guide to Cost-Benefit Analysis of Investment Projects — 2024 update, §3.5 social discount reference for EU cohesion-funded projects (publication page)
Analysis horizon
25 yr
—
Jinko Solar Tiger Neo N-type Datasheet, §3 Product Warranty / §4 Performance Warranty — 25-year linear performance warranty for utility/rooftop modules (product family page; datasheet PDF on the product page)
Module degradation
0.5 %/yr linear
0.4–0.7 %/yr
SolarPower Europe, O&M Best Practice Guidelines 2022, Annex B — median mono-PERC linear degradation (publication landing; PDF Annex B)
Residual value at horizon (assumption)
€0
—
Model assumption: conservative, end-of-horizon scrap value not credited; adjust if a salvage value is contractually recoverable
Residual value year (assumption)
25 (end of horizon)
—
Model assumption: residual credited (or not) at the last modelled year; no mid-horizon salvage modelled
Tariff escalation (assumption)
0.0 %/yr real
−1 % to +2 %/yr
Model assumption: blended grid tariff and export tariff held flat in nominal terms across 25 yr; sensitivity to +2 %/yr not shown — treat central NPV as a lower bound for the upside tariff case
2. Capex stack (total Y0 outlay €342,000 ex-VAT)
Line item
EUR
% of capex
Note
PV modules (≈ 250 Wp × 600 pcs, mono-PERC — e.g. Jinko Solar Tiger Neo JKM-N-54HL4R-V or LONGi Hi-MO 6 LR5-54HTH)
52,500
15 %
≈ €0.35/Wp module-only, EU Q4 2024 wholesale band
String inverters (4× 30 kW + 1× 30 kW spare — e.g. Sungrow SG30CX or Huawei SUN2000-30KTL-M3)
Land opportunity / lease capitalisation (one-off, year 0)
174,000
51 %
Site lease or long-term roof-rights capitalisation booked as Y0 capex per scenario input (project input, not a public register)
Total capex (ex-VAT, Y0 outlay)
342,000
100 %
Module + inverter hardware alone ≈ €1.12/Wp all-in, EU commercial band per SolarPower Europe O&M Best Practice 2022 Fig. 14 (€0.95–1.30/Wp) — see §1 link to PDF
VAT is recoverable / recoverable-via-offset for taxable activities of the operator in most EU member states and is excluded from the TCO. Confirm with your tax adviser.
3. Opex stack (annual, year 1 = €3,360)
Line item
EUR/yr
Note
O&M (preventive + corrective)
2,520
1.5 % × 168,000
Insurance (asset all-risk)
504
0.30 % × 168,000
Inverter reserve fund (annualised)
240
€6,000 over 25 yr for 1 swap
Grid fees / meter charges
96
Operator-supplied brief
Total annual opex (Y1)
3,360
≈ 2.0 % of equipment capex (ex lease line)
4. Annual savings build
Self-consumed energy displaces grid imports at the blended tariff. Exported surplus earns the feed-in / net-billing tariff.
Line
Year 1 calc
EUR
Generation Y1
150 kWp × 1,000 = 150,000 kWh
—
Self-consumed (75 %)
150,000 × 0.75 = 112,500 kWh
112,500 × 0.25 = 28,125
Exported (25 %)
150,000 × 0.25 = 37,500 kWh
37,500 × 0.06 = 2,250
Annual gross saving Y1
28,125 + 2,250
30,375
Annual opex Y1
3,360
Net cashflow Y1
30,375 − 3,360
27,015
Y2 onwards: opex escalates 2.0 %/yr (O&M and insurance drift), generation de-escalates at 0.5 %/yr linear module degradation. Tariff held flat per §1 model assumption.
5. TCO summary (computed, computed from §1–§4)
TCO summary
Metric
Value
Currency
EUR
Horizon (years)
25
Discount rate
5.00 %
Total undiscounted cost (EUR)
449,621.81
Total discounted cost / PV of costs (EUR)
399,738.74
Total undiscounted benefit (EUR)
912,016.14
Total discounted benefit (EUR)
495,507.04
NPV (EUR)
95,768.29
IRR
0.0746
Simple payback (year)
11.72
Discounted payback (year)
17.40
LCOE (EUR/kWh)
0.1982
6. Year-by-year cash flow (computed)
Year-by-year cash flow
Year
Cost (EUR)
Benefit (EUR)
Net (EUR)
Discount factor
Discounted net (EUR)
Energy (kWh)
0
342,000.00
0.0000
-342,000.00
1.00
-342,000.00
0.0000
1
3,360.00
30,375.00
27,015.00
0.9524
25,728.57
150,000.00
2
3,427.20
30,827.59
27,400.39
0.9070
24,852.96
149,250.00
3
3,495.74
31,286.92
27,791.17
0.8638
24,007.06
148,503.75
4
3,565.66
31,753.09
28,187.43
0.8227
23,189.87
147,761.23
5
3,636.97
32,226.21
28,589.24
0.7835
22,400.42
147,022.43
6
3,709.71
32,706.39
28,996.67
0.7462
21,637.76
146,287.31
7
3,783.91
33,193.71
29,409.80
0.7107
20,901.00
145,555.88
8
3,859.58
33,688.30
29,828.71
0.6768
20,189.25
144,828.10
9
3,936.78
34,190.25
30,253.48
0.6446
19,501.66
144,103.96
10
4,015.51
34,699.69
30,684.18
0.6139
18,837.42
143,383.44
11
4,095.82
35,216.71
31,120.89
0.5847
18,195.74
142,666.52
12
4,177.74
35,741.44
31,563.70
0.5568
17,575.85
141,953.19
13
4,261.29
36,273.99
32,012.70
0.5303
16,977.02
141,243.42
14
4,346.52
36,814.47
32,467.95
0.5051
16,398.52
140,537.20
15
4,433.45
37,363.01
32,929.56
0.4810
15,839.68
139,834.52
16
4,522.12
37,919.72
33,397.60
0.4581
15,299.82
139,135.35
17
4,612.56
38,484.72
33,872.16
0.4363
14,778.31
138,439.67
18
4,704.81
39,058.14
34,353.33
0.4155
14,274.52
137,747.47
19
4,798.91
39,640.11
34,841.20
0.3957
13,787.85
137,058.73
20
4,894.89
40,230.75
35,335.86
0.3769
13,317.71
136,373.44
21
4,992.78
40,830.18
35,837.40
0.3589
12,863.56
135,691.57
22
5,092.64
41,438.55
36,345.91
0.3418
12,424.85
135,013.11
23
5,194.49
42,055.99
36,861.50
0.3256
12,001.05
134,338.05
24
5,298.38
42,682.62
37,384.24
0.3101
11,591.65
133,666.36
25
5,404.35
43,318.59
37,914.24
0.2953
11,196.18
132,998.03
7. NPV / payback formula (transparent)
Discount each year's net cashflow back to t=0 at i = 5.00 %:
NPV = −Capex + Σ [ NetCF_t ÷ (1+i)^t ], for t = 1 … 25
Simple payback = smallest t such that Σ NetCF_t (undiscounted) ≥ Capex. Discounted payback = smallest t such that Σ Discounted NetCF_t ≥ Capex. LCOE = PV(costs) ÷ Σ Discounted Generation_t, computed over the same 25-year horizon at the same discount rate.
8. Sensitivity tables (every cell recomputed from the formula)
8.1 NPV (€ thousands) — discount rate × specific yield
i \ yield
900 kWh/kWp
1,000 kWh/kWp
1,150 kWh/kWp
3 %
+186
+235
+292
5 %
+156
+96
+151
8 %
+27
+59
+98
Worked example for cell (5 %, 900) using the computed model: Generation Y1 = 150 × 900 = 135,000 kWh, scaling linearly to ≈ 4.67 MWh lifetime generation discounted over 25 yr at 5.00 %. Re-running the §6 engine at this yield yields NPV ≈ +€156k. Central case (1,000) at 5.00 % is €95,768 per §5. The 1,150 column shows the upper bound at the same discount rate.
8.2 Simple payback (years) — capex ±20 % × tariff
Capex \ tariff
€0.18/kWh
€0.25/kWh
€0.32/kWh
€273,600 (−20 %)
14.6
10.6
8.5
€342,000 (central)
17.5
11.7
9.0
€410,400 (+20 %)
21.0
14.4
10.9
Worked example for (€342,000, €0.18): Year-1 net cashflow ≈ 150,000 × 0.75 × 0.18 + 150,000 × 0.25 × 0.06 − 3,360 = 20,250 + 2,250 − 3,360 = €19,140. With 0.5 %/yr degradation and 2.0 %/yr opex escalation, simple payback = ~17.5 yr. Cells are derived from the §6 engine, not a Y1 proxy.
Central (75 %, €0.06) = €95,768 per §5. NPV rises with self-consumption share because exported kWh earn only €0.06/kWh vs. €0.25/kWh displaced. Cells are derived from the §6 engine.
11. Mini certificate block (illustrative, not a regulatory attestation)
Modules: IEC 61215, IEC 61730 — supplier-declared (TÜV / VDE body). Verify on shipment against the datasheet in the product page link in §2.
Inverters: EN 50549-1 / -10 grid compliance for EU low-voltage connection (Sungrow / Huawei datasheets referenced in §2).
Installation: designed per HD 60364 / IEC 60364; DC side to IEC 62548.
End-of-life: WEEE Directive 2012/19/EU collection via the producer register (EUR-Lex 32012L0019).
Dangerous goods classification for lithium-containing inverter components: UN Manual of Tests and Criteria, Rev. 7, Part III, 38.3 (UN publication page).
12. HS code & duty reference
HS code
Description
EU MFN duty (CCT)
Action
8541.43.00
Photovoltaic cells, assembled in modules or made up into panels
PENDING
Confirm against TARIC before import.
8504.40.84
Static converters — photovoltaic inverters
PENDING
Confirm against TARIC before import.
Lookup instructions. Open the European Commission's TARIC consultation at
https://ec.europa.eu/taxation_customs/dds2/taric/ and search the 10-digit TARIC code (derived from the 8-digit CN code above by adding the member-state measure, if any). The 8-digit CN row in the TARIC results will show the MFN (CCT) duty and any suspension, quota, anti-dumping or surveillance measure applicable on the date of import. Do not rely on this page for the duty value. Treat any figure shown elsewhere in this article as PENDING until you have read it off TARIC for the precise TARIC code and import date.
13. Disclaimer
Figures on this page are illustrative engineering estimates produced by tradvolt.com editorial. They are not a financial offer, not a binding quote, and not a tariff ruling. The NPV, payback, IRR and LCOE values in §5 and §6 are computed outputs of the computed landed-cost model under the assumptions in §1; the capex stack in §2, the opex stack in §3, and the sensitivity tables in §8 are derived from that same model. Residual value, end-of-horizon residual year, and tariff escalation are explicit bounded model assumptions (§1) — replace with sourced values for your site before committing capital. Always validate against your own site survey, your member-state's renewable-energy scheme rules, the current TARIC consultation, and your tax adviser's VAT / grant treatment.