What the standard fixes
EN 15250 covers slow heat release appliances fired by solid fuel — the heat-retaining appliance, built heavy, fired for a short period and then left to give its heat back over many hours. It defines a test that measures that behaviour: the appliance is charged, burned, and then followed while it releases.
What it records is therefore different in kind from what the stove standards record. Instead of an output held steady over a run, it establishes how much heat the appliance gives back and over what period, which is the only way to describe an object whose whole purpose is the delay.
What it does not promise
It does not make heat-retaining appliances comparable to stoves on a single number, and any listing that presents them as if it did is misleading you. A figure describing a slow release and a figure describing a nominal output are not the same quantity.
It does not describe the finished appliance where one is built on site. A masonry heater assembled from a core and a mass is partly the builder’s work, and the mass is precisely the part that governs the release.
And it says nothing about the floor. These appliances are heavy in a way that is structural rather than inconvenient, and the load is the manufacturer’s figure and the building’s problem.
The documents that sit beside it
Where a heat-retaining appliance is sold as a complete unit it falls under the same market regulation as other solid fuel local space heaters. Where it is a core to be built around, the mass built around it lies outside what the standard assesses, and the page says so.
In German listings the vocabulary for this family overlaps heavily with the vocabulary for ordinary stoves and inserts — the word for a tiled stove insert, the word for a soapstone stove, the word for a storage stove. This site separates them by what the maker publishes rather than by the word in the title.
Where it appears on this site
It is cited on the appliances that publish it, which on the market this site surveys is a minority: most heat-retaining appliances are built rather than boxed, and the ones sold online are frequently cores and inserts. Where a listing calls an appliance heat-storing without publishing anything measured, the page prints the mass and the material and stops there.
Questions that keep arriving by post
Is a heavy stove automatically a heat-retaining appliance?
No. Mass helps, but a heat-retaining appliance is designed around the delay and is tested for it. A heavy stove with a soapstone cladding is still tested as a stove, and its figures are a stove’s figures. The page reports which standard the maker names.
Why do these appliances need a floor check?
Because the mass that makes them work is the mass the building has to carry, concentrated on a small footprint. The manufacturer publishes the weight; whether a particular floor takes it is not something a listing can know.
Can I compare one of these to a stove on kilowatts?
Not usefully. One figure describes heat produced while burning, the other heat released over hours after burning. Putting them in the same column is the kind of comparison this site exists to refuse.
Last reviewed 22 September 2026