Methodology: how WATTWEG checks prices

Who is behind it

WATTWEG is a product of Heidrich Digital, the trading name of Till Heidrich – Content Creation in Tostedt near Hamburg, Germany. Till Heidrich writes and is responsible for the articles. He drives electric, charges mostly at home, and uses public chargers mainly on family trips to the Netherlands and the coast. The app grew out of exactly that situation: wanting to know what a charge will cost without becoming a tariff expert.

AI tools help with research, data preparation and drafting. Every figure is checked against the linked primary source before it is published. We correct mistakes openly with a new date. Contact details are in the legal notice.

Interests: WATTWEG earns nothing from charging sessions, takes no money from operators or charge card providers and shows no ads. Revenue comes from the optional WATTWEG Plus purchase. More in Why WATTWEG earns nothing from your charging.

Terms as we use them

Ad hoc charging: Charging without a contract, paid at the charger (bank card, contactless, QR code). Required at all publicly accessible charge points since 13 April 2024 (AFIR Art. 5(1)).
Operator (CPO): The company that runs the charger and sets the ad hoc price.
Charge card provider (MSP, EMP): The company you have a contract with (card or app), which sets your price. Some are operators too.
Roaming: Charging with one provider's card at another operator's charger.
Idle fee: A per-minute charge once the car stays plugged in beyond a set time. In most tariffs we recorded, the clock starts when charging starts.

Where the figures come from

Operator ad hoc prices from open data: NDW DOT-NL (NL), MobiData BW and Mobilithek (DE), Fintraffic (FI), Spirii (DK, partly). Licences are listed under sources and licences.
Charge card and app tariffs from our own catalogue (72 products, 402 rules, version 2026-10-24.1). Every figure has a link, retrieval date and note. Overview at /en/tariffs/, file at /data/catalog.json.
Legal texts from the wording itself (AFIR, German price indication rules), linked in each article. Not legal advice.
Vehicle data from Open EV Data (MIT licence with attribution).

Not used: data from Chargeprice, Chargemap, Open Charge Map, comparison sites, blogs or other apps.

Tariff classes A, B, C

A, fixed price: a stated price per kWh by network, country or power.
B, formula on the charger price: the provider passes on the charger's price and adds a fee. Typical for Dutch charge passes.
C, app only: the price per charge point is shown only in the provider's app. We say so and show a range only if the provider publishes one.

Coverage measurement

On 24 October 2026 we counted how many rapid charge points of 50 kW or more along a route from northern Germany to Zwolle had an open price. Netherlands: 428 of 432 (99.1%). Germany: 617 of 1,221 (50.5%, up to 61.3% depending on how duplicates are merged). The largest gap between two locations with a price was 18.8 km.

How we calculate

Charging efficiency: DC 95%, AC 90%. You pay for kWh at the charger, not in the battery.
DC charging time: 1% steps, power per step is the lower of the car's charging curve and the charger's power.
Cold: below 5 °C 75%, below −5 °C 60% of the curve. A rough assumption, not a measurement.
Costs: each line rounded to the cent, total from rounded lines.
Subscription fees only count for a new tariff; subscriptions you already have count as zero.

Scope today

72 tariff products from 23 providers, 402 rules, 79 operator groups, 11 networks with prices from at least two providers. Checked on 24 October 2026. Not yet covered: E.ON Drive and Tesla membership (sites refused access), EDEKA, Kaufland, Shell Recharge NL (app only), Eneco, Bonnet, MAB Laadpas, IONITY annual plans.

Corrections

If a figure is out of date, please report it with the charger number, date, time, app and a screenshot.