Which smart radiator thermostat fits my valve?
Pick the connection type of your radiator valve. For each smart radiator thermostat, the tool shows whether it screws on directly, whether the adapter is in the box or sold separately, or whether the manufacturer does not confirm it.
The connection is identified by the shape and measurements of the valve, not by the radiator brand. If you are unsure, the identification guide walks you through measuring it.
Identify my valve’s connection
- Remove the current head (manual knob or thermostatic head) to expose the valve body.
- If the valve body has a thread, measure its outside diameter: about 30 mm means M30×1.5 (check the pitch, see the pitfalls below); about 28 mm means M28×1.5.
- If there is no thread but a clip fitting, measure the clip diameter: about 23 mm for Danfoss RA (count 4 notches) or Caleffi, about 26 mm for Danfoss RAVL, about 34 mm for Danfoss RAV, about 22.6 mm for Giacomini.
- If no measurement matches, it is a rarer connection: see the last pitfall below.
Smart radiator thermostats
Before you buy
- A manual valve (a plain knob, with no spring-loaded pin under the head) cannot take a thermostatic head: the valve body must be replaced first.
- M30×1.0 has the same diameter as M30×1.5 but a finer pitch: the head screws on for one turn, then jams. Do not force it.
- RA, RAV and RAVL are told apart by the clip diameter (about 23, 34 and 26 mm).
- Single-pipe systems and return valves (RTL): several manufacturers exclude them. Check before buying.
- The pin travel varies from one valve to another. If the radiator does not shut off or does not heat after fitting, run the head’s calibration again.
- Other, rarer connections (Vaillant 30.5 mm, Ista M32×1, Orkli M28×1, M38×1.5, M33×2.0): third-party adapter, to be checked.
Data collected on 10 November 2026 from the manufacturers’ documentation; box contents vary by country and product reference.
Method and limitations
This tool does not calculate anything: it looks up a table compiled on 10 November 2026 from the manufacturers’ documentation (see sources). Each head and connection pairing has one of five statuses: fits directly, adapter included, adapter sold separately, not supported by the manufacturer, or unconfirmed. Any pairing missing from the documentation consulted is shown as “unconfirmed”, never “not supported”. The list of heads is not exhaustive, and box contents vary by country and product reference. Whether a head suits your installation (valve, pipework) must still be confirmed with the manufacturer.
Sources
- Smart Radiator Thermostat X: adapters and compatibility (help articles 8949346 and 8949334) — tado°,
- Radiator Thermostat II: radiator thermostat adapter — Bosch Smart Home,
- Eve Thermo — Eve Systems,
- Radiator Thermostat E1 (product page) — Aqara,
- SONOFF TRV Compatibility (guide of 2 December 2024) — SONOFF,
- HmIP-eTRV-3 (product sheet) — Homematic IP,
- FRITZ!Smart Thermo 302 (manual) — AVM,
- evohome HR92 (product sheet) — Resideo,
- Danfoss Ally (guide) — Danfoss,
