How the price is calculated
wattslot shows the price of a kilowatt-hour as it appears on your bill, for every 15 minutes: the market price plus everything added to it. This page explains where each part comes from and what is left out.
What’s in the price
| Part | What it is | Source |
|---|---|---|
| Spot price | The market price for your price area (DK1 west of the Great Belt, DK2 east of it), set the day before in a daily auction. In 15-minute slots since 1 October 2025. | Energinet, DayAheadPrices |
| Grid tariff | Your grid company’s charge for the local grid. Most use Tarifmodel 3.0: low 00–06, high 06–17 and 21–24, peak 17–21, with higher prices in winter (October–March). | DataHub price list (DatahubPricelist) |
| Energinet’s tariffs | The transmission grid and system tariffs, the same all over Denmark. | DatahubPricelist |
| Electricity tax | The state tax on electricity (elafgift), as listed in DataHub. | DatahubPricelist |
| VAT | 25% of all of the above. | – |
What’s not included
Your supplier’s markup per kWh, and subscriptions from your supplier or grid company. They’re set in your contract, and fixed monthly fees don’t depend on when you use power. A fixed markup per kWh adds the same to every quarter hour, so the cheapest time stays the cheapest.
How it’s calculated
- Amounts are kept in whole millionths of a krone, so nothing is lost to rounding along the way. VAT is rounded once.
- Tariffs apply per local hour, so on the days the clocks change, a day has 92 or 100 quarter hours instead of 96.
- If a grid company’s tariff can’t be priced reliably — for example because the published data contradicts itself — wattslot shows the spot price only and says so, rather than a wrong total.
Coverage
- Tariffs for 31 of Denmark’s 35 grid areas are supported — 28 grid companies, covering 99.7% of metering points. The others show the spot price only.
- Germany, Norway (NO2) and Sweden (SE3, SE4): spot price only.
When it’s updated
- Tomorrow’s spot prices are usually published around 13:00. wattslot checks every 5 minutes from 12:50 to 14:30, then every half hour.
- Tariffs are checked every night.
- These pages are rebuilt just after midnight and once tomorrow’s prices are out. The price view at the top of the home page is always live.
Sources and licence
- Data from Energinet via Energi Data Service, under CC BY 4.0. The all-in prices are calculated by wattslot from that data; Energinet hasn’t checked or endorsed them.
- The code is open source on GitHub, and the data is available through the public API (OpenAPI document).