Calculation method and sources

Every calculator on the site uses the same data and the same calculation core. Exchange prices sit in five files, one per bidding zone, loaded by a script from the SMARD interface; last fetched on 24 October 2026. Taxes, levies and averages sit with their legal reference in a single file (params-2026.json); no amount is written into the code.

1. Exchange prices

SMARD, the electricity market platform of Germany’s Federal Network Agency, publishes the result of European day-ahead market coupling for Germany/Luxembourg, Austria, the Netherlands, Belgium, Poland and other zones, per quarter hour since October 2025, in euros per megawatt-hour. The data are licensed CC BY 4.0 with the credit “Bundesnetzagentur | SMARD.de”, shown under every calculator. We load the last six weeks in quarter hours, daily averages and monthly averages since 2018. A day counts as complete when it starts at midnight Berlin time, ends at 23:45 and has exactly 92, 96 or 100 quarter hours with no gap (96 on normal days, 92 or 100 when the clocks change). All times are Berlin time, which applies in all five zones. These are SMARD data from the Federal Network Agency, not EPEX SPOT data, and the site has no link with any power exchange.

2. From exchange price to all-in price

Germany. All-in = (exchange price + supplier markup + grid fee + electricity tax 2.05 ct/kWh + levies 2.946 ct/kWh + concession fee) × (1 + 19% VAT). The levies are the CHP levy (0.446 ct/kWh), the offshore grid levy (0.941 ct/kWh) and the special grid use surcharge (1.559 ct/kWh, category A up to 1 GWh). The concession fee is the cap for standard customers by municipality size (1.32 ct/kWh to 2.39 ct/kWh). The grid fee is an assumption: the 2025 average per federal state from the monitoring report (national: 10.72 ct/kWh); that average spreads the standing part of the grid charge over each kWh, so it sits slightly above the pure unit rate.

Example, daily average of 25 October 2026 (1.31 ct/kWh) with a 2 ct markup: net 20.62 ct/kWh, VAT 3.92 ct/kWh, all-in 24.54 ct/kWh.

Netherlands. All-in = (exchange price + purchase fee + energy tax 9.161 ct/kWh) × (1 + 21%). Network costs there are a fixed amount per connection and do not belong in an hourly price; nor does the annual tax reduction of €519.80 (net). Example 25 October 2026 (2.33 ct/kWh) with a 2 ct fee: 16.32 ct/kWh.

Austria, Belgium, Poland. We show the exchange price and add whatever you enter as “grid, levies and taxes” from your bill. We have not checked those countries’ charges line by line in the law, so we do not add them ourselves. Poland: converted to złoty at the ECB reference rate of 23 October 2026 (€1 = 4.3945 zł).

3. Cheapest hour, charging, comparison

The cheapest window is the run of quarter hours with the requested duration whose average price is lowest, searched from the current quarter hour to the end of the published prices. An appliance’s cost spreads its kWh evenly over its running time. Charging adds a loss (assumed 10%, editable). The tariff comparison lays your annual use, with a daily profile (flat or one of the example profiles), over the last 30 complete days and compares it with your fixed price; scaling that to a year is an assumption, since winter and summer are priced differently.

4. Reference figures

German household prices: 2025 monitoring report of the Federal Network Agency and the Federal Cartel Office (reference date 1 April 2025). Netherlands: CBS StatLine, table 85592NED, latest month September 2026, CC BY 4.0 licence.

5. Tests and updates

Every build checks the calculation core against fixed cases (price breakdown, clock-change quarter hours, cheapest window, charging time, comparison); a mismatch stops publication. scripts/update-data.mjs reloads prices five times a day (2:30 pm, 3:30 pm, 5 pm, 8 pm and 11 pm Berlin time) and the site is rebuilt afterwards. A series with a gap in the quarter-hour sequence is rejected, not patched, and every day must have exactly 92, 96 or 100 quarter hours. If today’s prices are missing, the calculator says so and names the day it uses instead; the latest day with prices is printed under every calculator. Taxes and levies are read again at each new year. Found an error? contact@kwhtoday.com.