Calculate with your own values
Defaults are illustrative scenarios, not current tariffs or measured savings. Use one currency for every amount; no exchange-rate conversion. Units are litres, °C and kWh.
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Method and example
Annual net saving = controllable heating cost × assumed saving percentage − additional running costs. Simple payback = purchase cost ÷ positive annual net saving. Example: 600 × 5% − 10 = 20 per year; 150 ÷ 20 = 7.5 years. Zero or negative net savings have no payback.
Start with your existing routine
If you already turn heating down when appropriate, the extra saving may be small. A basic programmable head can suit fixed hours; remote control may help with irregular attendance. Thermostat numbers represent target temperatures, not fixed power. Turning a valve to maximum does not necessarily warm a room faster. Keep the sensor clear of curtains and furniture.
Check the system before ordering
This guide covers thermostatic heads on water-filled radiators. Underfloor heating, electric radiators and boiler controls need different solutions. Identify the valve connection and any adapter from the installation instructions. Include every head, hub, adapter, battery and required subscription in the cost. Check whether schedules still work without internet access.
Use the part of the bill you can influence
Exclude hot water, fixed charges and other homes from the heating cost base. Shared-building billing can change how reduced heat use affects your own bill. The savings percentage below is an assumption, not a measured product claim. A milder winter alone does not prove that a new control works. Keep records for comparable use and weather.
In a rented home
Check your lease and the local responsibility for changes, keep original heads and follow the maker’s instructions. Do not loosen the water-carrying valve body. Ask the landlord or a qualified installer when compatibility is uncertain.
Common questions
Is a 20% saving guaranteed?
No. Savings depend on the previous settings, occupancy, building and billing method. Include a zero-saving scenario.
Does any smart head fit any radiator?
No. Check valve type, connector, adapter and the control system before buying.
Sources and limits
Technical sources below are in German, checked for the original guide on 4 October 2026. These adaptations do not establish local rental law, installation rules or tariffs. Follow local requirements and the instructions for your actual system.