What if the invoice does not itemise the lines?

Ask the supplier for a specified invoice or the contract's price sheet. Without line items you can still compare totals, but you cannot tell which line a battery would change or where a mismatch comes from.

Which lines does a battery change?

Mainly the peak lines (kW max, kW contract, Leistungspreis) and, on a dynamic contract, the energy line. The per-kWh lines change only through the battery's losses, which add to the kWh drawn.

How many months should be rebuilt?

All twelve. Annual mechanics — Germany's annual peak and price system, a Dutch contract overrun, a Romanian mid-year rate change — only show up across the full year.

Is a 2% mismatch on the total good enough?

It is Zorowatt's proposed default, chosen to stay well below the savings a battery case usually turns on. Regulated lines should match much more closely; a larger gap there usually means a wrong tariff version or a data problem.

Reading the C&I electricity bill line by line, and rebuilding it from the meter data

The three parts, by country

Netherlands: the supplier's energy (fixed, variable or dynamic); the regional grid operator's connection and transport charges (fixed, kW contract, kW max, kWh); energy tax per kWh and VAT. The ODE surcharge has been €0 since 2023, and the fixed tax reduction of €519.80 a year (2026) applies only to properties with a verblijfsfunctie (Belastingdienst; Liander 2026).
Germany: the supplier's energy; the grid operator's Leistungspreis and Arbeitspreis; the KWKG levy, the offshore grid levy, the surcharge for special grid use, the electricity tax, the concession fee and VAT (NEW Netz 2026; Stadtwerke Homburg, levies 2026; §3 StromStG).
Romania: the supplier's energy; transport, system services and distribution per MWh; green certificates, the cogeneration and CfD contributions, excise and VAT (MET notice of the 2026 tariffs).

The billing quantity behind each line

Fixed charges: per month or per day, a lookup, no meter data needed.
Energy and per-kWh network charges: the sum of kWh in each time window (day/night, peak/off-peak), or every interval times its price on a dynamic contract.
Monthly peak (NL kWmax): the highest 15-minute kW of the month.
Annual peak (DE Leistungspreis): the highest 15-minute kW of the year, priced by the full-load hours (annual kWh ÷ annual peak).
Contracted capacity (NL kW contract): the agreed kW, plus the overrun rule if the site exceeded it.
Degressive taxes (NL energy tax): the year's kWh, split over the brackets.

Worked example: one month on Liander's tariff

Illustrative, not a real customer: a medium-voltage site on Liander's 2026 tariff, 150,000 kWh in the month, a highest quarter-hour of 400 kW and a 400 kW contract (assumptions). Network charges, excluding VAT (Liander 2026):

Fixed transport charge: €36.75.
kW contract: 400 × €2.29 = €916.00.
kW max: 400 × €3.57 = €1,428.00.
Transport kWh: 150,000 × €0.0226 = €3,390.00.
Transport total: 36.75 + 916.00 + 1,428.00 + 3,390.00 = €5,770.75. The periodic connection charge comes on top and depends on the connection's capacity (for example €162.17 a month for more than 1 up to 2 MVA).

Energy tax is set on the year. At 12 × 150,000 = 1,800,000 kWh (assumption) and the 2026 brackets (Belastingdienst): 10,000 × €0.09161 = €916.10, plus 40,000 × €0.06671 = €2,668.40, plus 1,750,000 × €0.03735 = €65,362.50 — €68,947.00 for the year. The supplier's energy depends on the contract and has to be read off the invoice or the contract.

How close is close enough

Zorowatt's proposed tolerances, estimates to be calibrated on real bills:

Regulated per-unit charges and taxes (kWh, kW max, kW contract, energy tax, Stromsteuer, excise, levies): ±1%. They are a published rate times a billed quantity.
Supplier energy: ±3%, because profile costs, imbalance and pass-through items are often not itemised.
Fixed charges: exact.
Every line: ±5% by default. The total excluding VAT: ±2%.

When a line does not match

Each deviation outside the tolerance gets one of six causes:

Tariff version: the wrong year, category or price system (Germany's below/above 2,500 hours).
Estimated reading: the invoice used an estimate the data does not have, or the other way round.
Data gap: missing intervals in the export.
Proration: a rate changed during the billing period. Romania's 2026 tariff notice compares its values with those of both 1 January and 1 September 2025, which implies a mid-year change, and the cogeneration contribution changed on 1 November 2025.
Unknown supplier fee: a charge on the invoice that is in no tariff sheet.
Invoice error: a real finding for the client.

Country details that catch people out

Netherlands: Stedin corrects the measured consumption of a medium-voltage connection metered on the low-voltage side by 1.4% (Stedin regulation 2026, art. 5(11)). An overrun of the contracted kW can raise the contract from the month of the overrun, retroactively if the contract was lowered within 12 months (Liander 2026).
Germany: the price system follows the full-load hours, so bill both systems and check which one the invoice used.
Romania: the green-certificate line uses the quota times the previous month's average certificate price; in 2025 that was 0.496 × 146.2532 lei = 72.54 lei per MWh (MET 2025 notice).
Enexis states its fixed and contracted-capacity charges per year (Enexis, 1 Jul 2026); Zorowatt bills them as 1/12 per month, an assumption to check against the invoice.

Why it is worth the effort

A battery's savings are the difference between two bills computed the same way. If the baseline is wrong, the difference is too. In one public case, a tool showed about $20,000 a year of savings for a system with almost no solar; after a demand charge entered twice was corrected, the savings fell to about $1,000 and the NPV turned negative (SAM forum).

The Workspace rebuilds every line from the meter data and the tariff version it names, puts it next to each month's invoice and gives every deviation a cause code.

Frequently asked questions

What if the invoice does not itemise the lines?: Ask the supplier for a specified invoice or the contract's price sheet. Without line items you can still compare totals, but you cannot tell which line a battery would change or where a mismatch comes from.
Which lines does a battery change?: Mainly the peak lines (kW max, kW contract, Leistungspreis) and, on a dynamic contract, the energy line. The per-kWh lines change only through the battery's losses, which add to the kWh drawn.
How many months should be rebuilt?: All twelve. Annual mechanics — Germany's annual peak and price system, a Dutch contract overrun, a Romanian mid-year rate change — only show up across the full year.
Is a 2% mismatch on the total good enough?: It is Zorowatt's proposed default, chosen to stay well below the savings a battery case usually turns on. Regulated lines should match much more closely; a larger gap there usually means a wrong tariff version or a data problem.

Related guides

Sources

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 are Zorowatt's own estimates. VAT is left out because its rate was not verified on official pages in Zorowatt's research.

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