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ACM: maximum heat tariffs are less dependent on price fluctuations as a result of new calculation method

Starting this year, the Netherlands Authority for Consumers and Markets (ACM) will use three different reference dates (September, October, and November 2025) when determining the maximum heat tariffs. Previously, these tariffs were based on the average natural-gas price for a one-year contract starting on January 1 using a reference date of the end of November.

The prices on the wholesale market for natural gas can fluctuate considerably, for example, as a result of geopolitical tensions or seasonal influences. By using three reference dates and calculating an average thereof, these price fluctuations are flattened. This ensures stabler and fairer tariffs, which are in line with the actual costs for consumers.

The maximum heat tariffs are linked to the average costs that a household with a gas-fired boiler has to pay for heating and hot tap water. This is also called the natural-gas reference price or the ‘no-more-than-otherwise principle’ (in Dutch: niet-meer-dan-anders principe). The method that ACM must use for determining the maximum tariffs has been laid down in the Dutch Heat Act (in Dutch: Warmetewet), the heat decision (in Dutch: warmtebesluit), and the heat regulation (in Dutch: warmteregeling). The Dutch legislature changed the heat decision last year, thereby enabling ACM to use three reference dates when setting the maximum tariffs per gigajoule (GJ).

ACM determines the heat price per GJ for a specific calendar year on the basis of the average price that households have to pay for a one-year contract for the supply of natural gas. Going forward, ACM will use the following reference dates:

  • Reference date of September 19, 2025, one-year contract from January 1, 2026 through December 31, 2026, with a weight of 1/3, based on the top ten natural-gas suppliers that offer a one-year contract for 2026 on that date.
  • Reference date of October 20, one-year contract from January 1, 2026 through December 31, 2026, with a weight of 1/3, based on the top ten natural-gas suppliers that offer a one-year contract for 2026 on that date.
  • Reference date of November 20, one-year contract from January 1, 2026 through December 31, 2026, with a weight of 1/3, based on the top ten natural-gas suppliers that offer a one-year contract for 2026 on that date.

In addition to the maximum heat tariff per GJ, ACM also sets the maximum tariffs for the fixed costs, the maximum metering tariffs, and the maximum tariffs for heat interface units. ACM will collect the necessary information for these calculations in the coming months, and expects to publish the maximum tariffs for the coming year by the end of November.

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