Levelised cost of energy calculator
Works out what your own kilowatt-hour costs — with the annual yield from your location instead of a round number. For 10 kWp at 10,150 euros near Berlin that is 7.55 ct/kWh over 25 years. The naive calculation without discounting and degradation lands at 5.30 ct, 30 % too low. For comparison: grid power costs 31.1 ct, the feed-in tariff pays 7.7 ct.
The formulas behind the calculator
Every number above can be recomputed: the full calculation path, all assumptions and the data source with retrieval date — plus cross-validation against independent references. Disclosed, not claimed.
An estimate based on the stated assumptions. The final design must be checked by a qualified professional against the rules that apply where you are.
Data as of: 2026-08-06
| Step | Formula | Value | Provenance |
|---|---|---|---|
| Present value of costs | I_0 + Σ (M_t + F_t)/(1+r)^t | 12,801 Waehrung | exact |
| Present value of the energy | Σ E_1*(1-d)^(t-1)/(1+r)^t | 169,560 kWh | exact |
| Levelised cost of electricity | NPV(costs) / NPV(energy) | 0.075496 Waehrung/kWh | exact |
- Formula
LCOE = (I₀ + Σ (M_t+F_t)/(1+r)^t) / (Σ E₁·(1−d)^(t−1)/(1+r)^t)- Valid for
- Annual resolution, constant degradation. The specification's reference case is reproduced: €10,150 investment, 1.5%/a operations, r = 3%, 25 years, 10,000 kWh → numerator €12,801, discounted denominator 165,328 kWh → 7.74 ct/kWh; an undiscounted denominator would give 5.43 ct (−29.8%). Discount band 2–6%: 7.10 to 9.90 ct. German EEG rate 08/2026 (7.70 ct) as reference line.
- Not covered
- Tax effects, financing side costs, residual value, power-price escalation (calculator 50), inverter replacement as a separate item (bundled into operating cost here — calculator 41 itemises it).
- Data sources
- Bundesnetzagentur SMARD electricity price analysis, StromAuskunft price index (as of 2026-08-06) and EEG remuneration rates per § 48 EEG 2023 · Q3/2026 (EEG-Sätze H2/2026) · retrieved 2026-08-06
Frequently asked questions
What does a self-generated kilowatt-hour of solar power cost?
In the reference case (10 kWp for €10,150, 25 years, 3% discount rate) it is 7.55 ct/kWh — computed correctly with both numerator AND denominator discounted. Depending on the discount rate (2–6%) the value ranges from 7.10 to 9.90 ct. For comparison: grid power averages 31.1 ct for existing customers in Germany.
Why do other LCOE calculators deviate by 30%?
Because they discount only the costs but not the energy: 235,560 undiscounted instead of 165,328 discounted kilowatt-hours in the denominator give 5.43 instead of 7.55 ct — 29.8% too cheap, and the error always points the same way. This calculator shows both values side by side so the difference stays visible.
Is feeding in still worth it?
Economically, practically no: since 1 August 2026 the German feed-in tariff (7.70 ct for partial feed-in up to 10 kWp) sits slightly BELOW the reference case's cost of energy (7.55 ct). Every exported kilowatt-hour is a slight loss. The entire return of a German PV system comes from self-consumption — 31 ct saved instead of 7.70 ct earned.
Which discount rate should I choose?
There is no „correct“ choice — the three presets answer different questions: 0% means „money in versus money out, no interest comparison“. 3% means „I would otherwise have invested the money safely“. If you finance the system, enter your effective loan rate. The choice moves the result by over 20% — which is why the calculator always shows the band.
Are inverter replacement and insurance included?
As a lump sum, yes: the annual operating cost (rule of thumb 1–2% of the investment) bundles insurance, maintenance, metering and reserves for the inverter. To see the replacement as a dated single item, use the payback calculator — there it appears as a visible setback in year 13.
Is the LCOE the same as the price at which the system pays off?
No — the LCOE is the cost price per kilowatt-hour over the lifetime. Whether the system pays off is decided by comparison: every self-consumed kilowatt-hour saves the power price (31.1 ct), every exported one earns the tariff (7.70 ct). If the LCOE sits in between, only self-consumption makes money — exactly what the chart with the reference lines shows.
What does my own solar kilowatt-hour cost?
For 10 kWp at 10,150 euros in the Berlin region the calculator finds 7.55 ct/kWh over 25 years — with discounting, degradation and operating costs. Grid power costs 31.1 ct by comparison. Every self-consumed kilowatt-hour therefore saves about 23.6 ct. The feed-in tariff at 7.7 ct sits only just above the generation cost — exported power barely carries itself.
Why is the naive calculation 30 percent too low?
Because it omits two things. First degradation: in year 25 the modules deliver about 12 percent less than in year one, so the denominator shrinks. Second discounting: a kilowatt-hour twenty years from now is worth less today than one tomorrow. Investment divided by yield times lifetime gives 5.30 ct in the example — the full calculation gives 7.55 ct. That difference is not a nicety but almost a third.
How much does system size affect the levelised cost?
Strongly, as long as the investment does not grow with it. At a constant 10,150 euros, 5 kWp gives 15.05 ct/kWh, 10 kWp gives 7.55 ct and 20 kWp gives 3.76 ct. In practice the investment does rise — but less than proportionally, because scaffolding, electrical work and commissioning barely depend on module count. That is exactly where the advice to fill the roof comes from.
Is exporting worth it at these generation costs?
Only just, and it depends on the site. At 7.55 ct generation cost and a 7.7 ct tariff, 0.15 ct per exported kilowatt-hour remains — effectively break-even. At a poorer site or with a more expensive system it tips into the red. So the statement is not “exporting does not pay” but: exporting carries itself, self-consumption earns. The gap between 7.7 ct and 31.1 ct is the real lever.
Which discount rate should I use?
The one matching your alternative. Paying from your own capital, use the return the money would otherwise have earned — 2 to 4 percent is usual. Financing it, use the loan rate. Using 0 percent ignores the time value and flatters the result. The calculator therefore reports a band from 2 to 6 percent, so the spread stays visible instead of disappearing into a single figure.