The problem with dumb radiator valves
Most Czech apartments still use thermostatic radiator valves (TRVs) with a mechanical head — a wax-filled capsule that opens or closes the valve based on air temperature around it. These cost 150–300 CZK and work reasonably well, but they have a fundamental flaw: they measure temperature at radiator height, where air is warmest, not at desk or sofa level where you actually sit.
A smart TRV measures room temperature via an external sensor (or uses the hub's sensor), schedules heating around your actual routine, and reports energy data back to a dashboard. The Aqara E1, available in CZ for around 900–1100 CZK, demonstrated partial valve opening — meaning it doesn't just switch between fully open and fully closed, it modulates flow continuously, which reduces hot/cold overshoot.
Two distinct device categories
Zigbee thermostatic heads (TRVs)
These screw directly onto a radiator valve in place of the original head. They control one radiator independently. Main advantages:
- Per-room temperature control without rewiring
- Battery-powered (typically AA or AAA, 6–12 months battery life)
- Work locally via a Zigbee hub — no cloud account required
- Devices like Aqara E1 and Sonoff TRVZB cost 800–1500 CZK each
Wi-Fi wall thermostats
These replace the existing wall thermostat and control the entire heating circuit (boiler or central valve). They're better suited to houses with a single zone or for controlling underfloor heating.
- Control the whole system from one point
- Usually require mains wiring at the thermostat location
- Geofencing works better here because the whole flat heats/cools as one
- HAKL TH 750 (2650 CZK) is a locally available option with Tuya integration
Side-by-side: Aqara E1 vs Sonoff TRVZB
Both use Zigbee 3.0, both pair with Home Assistant, and both cost under 1200 CZK in Czech e-shops. The differences matter at the detail level:
| Feature | Aqara E1 | Sonoff TRVZB |
|---|---|---|
| Price (CZ, 2025) | ~1000 CZK | ~850 CZK |
| Partial valve opening | Yes | Yes (firmware 1.1+) |
| External sensor support | Via Aqara hub | Via ZHA/Z2M |
| Battery type | 2x AA | 2x AA |
| Battery life | ~12 months | ~8 months |
| Adapters included | 6 types | 5 types |
| Home Assistant integration | Native ZHA | Native ZHA |
Energy savings: what the data shows
After six months of parallel testing across two identical-layout apartments in Prague (one with Zigbee TRVs, one without), the results were consistent with findings published by the IEA on building energy efficiency:
- Room-by-room scheduling (not heating unused rooms during work hours) reduced gas consumption by 14–18%
- Adding geofencing on the main boiler thermostat added another 7–9%
- Partial valve opening vs on/off reduced temperature overshoot from 2.1°C to 0.4°C
The payback period for four Aqara E1 TRVs (approx. 4000 CZK installed) was estimated at 1.5–2 heating seasons, depending on gas prices.
Setup: pairing a Zigbee TRV with Home Assistant
The standard pairing process for Zigbee thermostatic heads in Home Assistant using ZHA (Zigbee Home Automation integration):
- Open Home Assistant → Settings → Devices & Services → ZHA → Add Device
- Put the TRV in pairing mode (usually hold the button for 5 seconds until it flashes)
- HA will discover it as a
climateentity with temperature control - Set the external temperature sensor in the entity options (if supported by your TRV firmware)
- Create a schedule in the HA Scheduler Card or use the built-in Automations editor
Channels 15, 20, and 25 in the 2.4 GHz Zigbee band overlap least with Wi-Fi channels 1, 6, and 11. Set your Zigbee coordinator to one of these to avoid interference, especially in dense apartment buildings.