What a battery feasibility study contains, and what it is not

1. The data check

Everything rests on the meter data, so the study starts there: 12 months of 15-minute interval data for the grid connection. The check looks for gaps, duplicates, daylight saving days, kW read as kWh, meter registers instead of interval values, spikes and stuck readings.

• Zorowatt calls a dataset good enough for a study when it covers 12 months with at least 90% of the intervals measured. That threshold is Zorowatt's own estimate, not a standard.
• Every repair is a proposal you accept or reject, never automatic: interpolate a gap of up to an hour, fill a longer one from the same weekday's profile, or leave it out.
• The report carries a data-quality appendix: the share measured, the share filled and by which method, the issues found and the decisions taken.

2. The bill, rebuilt from the data

The study rebuilds every line of the site's bill from the meter data and the tariff, then compares it with the real invoices, month by month. A battery's savings are the difference between two bills computed the same way: without the battery and with it. If the computed baseline does not match what the site actually paid, the savings cannot be trusted either.

• Zorowatt's proposed tolerance is ±2% on the total excluding VAT and ±5% per line, tighter for regulated per-unit charges and taxes. These bands are an estimate, to be calibrated on real bills.
• Each deviation outside the tolerance gets a cause: wrong tariff version, an estimated meter reading, a data gap, a rate change in the middle of a billing period, a supplier fee that is not on the tariff sheet, or an error on the invoice — which is a real finding for the client.

3. Sizing

The right battery is found by trying many: several energy sizes (kWh) times several power ratings (kW), for example 8 × 5 = 40 combinations. Each one is simulated through the year, billed and run through the financials. The result is a curve of net present value against size, so you can see where a bigger battery stops paying for itself.

4. A year of dispatch

For each size, the battery is simulated every 15 minutes for the whole year. Two kinds of dispatch matter:

• The expected case: a rule-based controller that does what a site's energy management system does, without knowing the future. Zorowatt's report numbers come from this case.
• The upper bound: an optimiser with perfect foresight of the year's load and prices. It shows the most the battery could ever earn; it is never the headline. The ratio between the two shows how much a real controller captures.
• In Zorowatt the battery starts the year empty and may not end it emptier, so stored energy never flatters the savings.

5. The financials

Installed cost, maintenance, capacity fade, a replacement when the battery reaches its end of life, the discount rate and price escalation turn the yearly savings into payback, NPV and IRR. See NPV, IRR and payback for a C&I battery for the method with a worked example.

6. Assumptions and limits

A study lists what it assumed and what it cannot know: the tariff version and its source, the battery's cost and where it came from, the degradation assumption, and the tariff changes that are known but not final.

• Netherlands: the ACM's draft decision of 8 October 2026 would make the kWmax charge time-weighted from 1 January 2028. It is a draft, open for comments until 18 November 2026 (ACM draft).
• Germany: the StromNEV expires on 31 December 2028, and the AgNes reform would replace the Leistungspreis for large consumers with a booked-capacity price from 2029; the final decision is pending (Bundesnetzagentur, 27 May 2026).

What a study is not

• Not a guarantee: a future year will not be the same as the past one, and the result is only as good as its inputs.
• Not investment, financial, tax, legal or engineering advice.
• Not a grid operator's connection study, an installer's design or a protection design. It does not control a battery or trade energy.

Zorowatt's disclaimer sets out these limits in full.

Start with the free meter data checker to see whether a site's data is good enough. The Workspace then does the whole study in the browser and writes the report; your first site analysis is free.

Related guides

• The four ways a business battery earns
• What to ask your client for before a battery study
• What makes a battery report survive the CFO

Sources

• ACM, draft code decision on time-dependent tariffs for large connections, 8 Oct 2026
• Bundesnetzagentur, AgNes press release, 27 May 2026
• Zorowatt disclaimer

Last checked: 2026-10-30. Every figure in this guide comes from the source linked next to it, with the retrieval date Zorowatt's research recorded (28–30 October 2026), or from arithmetic shown step by step. The tolerance bands and the 90% coverage threshold are Zorowatt's own estimates.