BESS-Market
Tool 03

ROI Calculator

The ROI Calculator models the economics of your storage project: CAPEX and OPEX against a revenue stack of balancing services (FCR, aFRR, mFRR), arbitrage (day-ahead, intraday) and peak shaving. From this it derives IRR, NPV, payback, DSCR and the levelized cost of storage — in base, optimistic and pessimistic scenarios.

Price assumptions are indicative market averages for Germany (as of 2025/2026). You can adjust every input to your project assumptions; the calculation runs locally in your browser.

More about operations & trading

How it works

  1. 01

    Enter project parameters: CAPEX, OPEX, WACC, lifetime, degradation, efficiency.

  2. 02

    Select revenue streams: balancing services, arbitrage, peak shaving — with risk flags.

  3. 03

    Optionally add debt: leverage, interest rate and tenor for the DSCR view.

  4. 04

    Read the result: scenarios, key metrics, revenue breakdown and sensitivity to WACC and revenue level.

Loading market data …
This calculator is designed for 1–30 MW projects. Revenue and cost assumptions are a pre-feasibility view for the mid-market — not a bankable report.

Load an example project

The battery shares grid connection and land with a solar plant. That brings additional energy (recovered curtailment), saves connection costs — and shifts solar power out of negative-price hours.

Your battery

System design

Duration follows from power and capacity — you can also pick it directly.

Revenue segments

Project assessment

Not viable under these assumptions

NPV is negative in all three scenarios. That is an honest statement about these assumptions, not about storage in general. Check the levers:

A final investment decision before 1 Jan 2027 decides on the grid fee exemption.

NPV base:
€ -2.39 M
IRR base:
2.1 %
Min. DSCR:
0.87
Annual revenue (indicative)
€ 618 kper year
€ 62 k per MW€ 31 k per MWh
Pessimistic
€ 494 k
Base
€ 618 k
Optimistic
€ 742 k

Where the money comes from

Share of annual revenue · hover shows the price source
  • FCR (primary reserve)€ 305 k
    € 30 k/MWeffective capture: 21 %regelleistung.net, Ø 365 days, As of 2026-09-21
  • aFRR (secondary reserve)€ 101 k
    € 10 k/MWeffective capture: 18 %regelleistung.net, Ø 365 days, As of 2026-09-21
  • Day-ahead arbitrage€ 212 k
    € 21 k/MWeffective capture: 21 %Energy-Charts, As of 2026-09-21

How realistic is the market capture?

60 %

Not every battery earns full remuneration in every market. The slider dampens all segments — more in tight markets, less in liquid ones.

Small market (a few GW). Large batteries must split their power; the longer the duration, the lower the share that can be reserved.

Committed power60 %

The selected segments fit within the available power.

Key figures

EBITDA
€ 583 k
EBITDA margin: 94 %
Investment
€ 5.60 M
Operating cost
€ 35 k

What if prices move?

Each row varies only that one driver; “total” moves all of them at once.
Varied driver−20 %today+20 %
FCR (primary reserve)€ 557 k€ 618 k€ 679 k
aFRR (secondary reserve)€ 598 k€ 618 k€ 638 k
Day-ahead arbitrage€ 575 k€ 618 k€ 660 k
Total€ 494 k€ 618 k€ 742 k

1h, 2h or 4h?

More capacity buys arbitrage revenue but stretches payback — with your inputs the sweet spot is 1h.

Project model over 20 years

Tier 1 · Public

Including grid connection contribution and grid fees, degradation and augmentation, and falling revenues as storage is built out. Result as a range, the way banks want to see it.

Upsidelow buildout, low grid fees
NPV
€ -1.61 M
IRR
3.8 %
Payback
14.2 yrs
Min. DSCR
1.02
Baseyour assumptions
NPV
€ -2.39 M
IRR
2.1 %
Payback
16.5 yrs
Min. DSCR
0.87
Downsidehigh buildout, high grid fees, −1 pp availability
NPV
€ -3.57 M
IRR
-0.9 %
Payback
> 20 yrs
Min. DSCR
0.66

Depending on the scenario, payback lies between 14.2 yrs and > 20 yrs. NPV is positive in 0 of 3 cases.

Deliberately conservative

The model starts at € 62 k revenue per MW and year (utilisation 60 %). Published revenue indices for Germany were around €95,000–200,000 per MW and year in 2026 — but that is the theoretical maximum with perfect trading. Revenues actually achieved are well below, depending on optimiser, strategy and availability.

A negative NPV here means: under these conservative assumptions the project does not pay for itself. It does not mean storage projects are uneconomic in general.

Set utilisation to what your optimiser offers or guarantees, and check tolling (tab “Market”).

Exemption unclear71 days left until the FID cut-off 1 Jan 2027 (draft)

Without a documented FID before 1 Jan 2027, grandfathering is open. Base case counts it at 50 %; upside and downside show both outcomes.

Grid operators’ allocation procedures and deadlines →
  • — Grid connection contribution € 1.00 M (100.00 €/kW, reference value) — 18 % of the plant investment
  • — Grid connection (indicative): € 345 k (range € 241 k–€ 517 k) — route 0.0 km incl. detour factor 1.3, station, 15 % contingency. Route must be checked separately.
  • — Grid fee from 2029: € 28 k per year (base), total over lifetime € 910 k
Cumulative cash flow per scenario● Upside € 3.06 M● Base € 1.59 M● Downside € -617 k
0-6.95 M3.06 M05101520

Professional project model — with a free account

Set every parameter, compare augmentation strategies, model tolling, financing with DSCR and the tornado analysis.

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Bankable screening (hourly dispatch simulation, financing structure, due diligence) is provided through specialised partners.
Assumptions & sources

Plausibility of your inputs

1 point undermine the calculation.

Each row tests one assumption and says what it rests on.

  • Power, capacity and duration agreeOK

    20 MWh at 10 MW gives 2.0 h — a 2h system is selected.

  • Power sold only onceOK

    The segments commit 60 % of the power; anything over-booked is shared proportionally.

  • Segment mix suits the durationOK

    The selected segments suit the duration.

  • Market capture realistically setOK

    60 % is a cautious assumption.

  • Investment within the usual rangeOK

    280 EUR/kWh. Turnkey including grid connection is currently 120 to 450 EUR/kWh.

  • Operating cost within the usual rangeOK

    3,500 EUR per MW per year. Typical is 1,000 to 8,000 EUR/MW.

  • Paid back before the battery is replacedReview

    Payback after 16.5 years, with the first battery replacement due in year 12 — the replacement lands before break-even.

  • Project carries across the periodCritical

    Net present value € -2.39 M — at 7 % cost of capital the project does not earn its financing.

  • Prices are currentReview

    Prices as of 2026-09-21, which is 31 days old. Reserve and spot prices move a lot — a decision deserves fresher figures.

Data basisFCR, aFRR and mFRR — regelleistung.net (German TSO data center) · As of 2026-09-21Day-ahead spread — Fraunhofer ISE Energy-Charts (CC BY 4.0) · updated …These are market averages, not a revenue guarantee.

Result as a PDF report

All inputs, the revenue stack, the sensitivity matrix and the sources on one page — ready to forward to investors or feed into your own model.

Build the project

Want to build this battery? We connect you with the right partners.

Send us your calculated project. We review it and connect you with suitable integrators, EPC partners, optimisers or financiers — independent and free of charge for you.

  • Reply within two business days
  • Only selected providers that fit your project
  • Your contact details never go to third parties without your okay

Methodology and scope

Scenarios stress revenues by ±30 %. Revenues scale with remaining capacity (degradation). DSCR is computed from annual pre-debt cash flow against annuity debt service. All values are indicative and do not replace a bankable revenue report.

Next step

Start your project or talk to us — we will connect you with the right contact.

Start ProjectContact