Heating is the single biggest energy expense in most homes. A smart thermostat helps, but connecting it to Home Assistant turns it into something much more powerful: a climate system that knows when you're home, which rooms need heat, and when to stop burning money warming an empty house.
Jump to a section
A Nest or tado thermostat is a good start. But on its own, it's basically a fancy timer. Connect it to Home Assistant and suddenly it can react to motion sensors, door contacts, weather forecasts, and your phone's location. That's when real savings kick in.
Most thermostats heat on a schedule. But schedules don't know you left early or came home late. Home Assistant uses your phone GPS and motion sensors to detect presence in real time. No more heating an empty house.
Why heat 6 rooms when you're only using 2? TRVs on individual radiators let Home Assistant heat just the rooms that need it. The guest bedroom stays cool. Your office warms up before your first meeting.
Pair your thermostat with Home Assistant's energy dashboard and you can see exactly how much each heating decision costs. That feedback loop changes how you think about comfort vs. waste.
Not all smart thermostats play nicely with Home Assistant. Here's what actually works, and the trade-offs you should know about.
~€220 / Cloud API / Boiler control
Good hardware, uncertain future. Works with HA but you're trusting Google to keep the API alive.
~€200 / Cloud API / Boiler + TRVs
Popular in Europe. The HA integration works well, but you're paying for features that Home Assistant can do for free.
~€30 total / 100% Local / Boiler control
The tinkerer's choice. A Shelly 1 relay switches your boiler, a Zigbee temp sensor provides readings, and HA's generic thermostat component ties it all together. Total cost: under 30 euros.
~€250 / Cloud + HomeKit / HVAC systems
Strong option in North America where HVAC is standard. Less common in European boiler/radiator setups.
A smart thermostat controls your boiler. TRVs (thermostatic radiator valves) control individual radiators. Together, they give you room-by-room climate control. This is where the serious savings happen.
~€45 / Wi-Fi / Local API
Fully local, no hub needed. Built-in temperature sensor, open window detection. The Home Assistant integration is native and reliable. Best value for money in the TRV market right now.
~€70 / Proprietary / Cloud API
Sleek design, good build quality. Works well with the tado thermostat as a complete system. But it's cloud-dependent and the subscription model for auto-assist is annoying. You're paying a premium for polish.
€20-35 / Zigbee / 100% Local
Budget friendly and fully local via Zigbee2MQTT or ZHA. The Sonoff TRVZB is a standout at around 25 euros. Calibration can be hit or miss, and the built-in temp sensors tend to read high (use an external sensor). But for the price, they're excellent.
The temperature sensor built into a TRV sits right next to the radiator, so it reads 2 to 4 degrees higher than the actual room temperature. Place a separate Zigbee temperature sensor (like the Aqara WSDCGQ11LM, about 12 euros) in the middle of the room and use Home Assistant's generic thermostat to control the TRV based on the external sensor's reading. This one tweak dramatically improves comfort and accuracy.
These are the automations that pay for themselves. Each one targets a specific waste pattern and eliminates it.
Use the person entity in Home Assistant (based on phone GPS or router presence detection) to drop the temperature to 16°C when everyone leaves. When someone comes home, the heating kicks back up. Most families waste 2 to 4 hours of heating on empty houses daily.
automation:
trigger:
- platform: state
entity_id: zone.home
to: "0" # everyone left
action:
- service: climate.set_temperature
target:
entity_id: climate.living_room
data:
temperature: 16A door/window contact sensor costs 8 euros. When a window opens, immediately turn off the heating in that room. When it closes, restore the previous temperature. Without this, your boiler fights the cold air pouring in and you're literally heating the street.
automation:
trigger:
- platform: state
entity_id: binary_sensor.bedroom_window
to: "on" # window opened
for: "00:01:00" # 1 min grace period
action:
- service: climate.set_hvac_mode
target:
entity_id: climate.bedroom_trv
data:
hvac_mode: "off"If your phone alarm is set for 7:00, start heating the bedroom and bathroom at 6:30. Home Assistant can read your next alarm time from your phone (via the companion app). You wake up to a warm room without running the heating all night. Works particularly well with TRVs since you only heat the rooms you'll use first thing.
Home Assistant can pull weather forecasts and adjust your heating schedule accordingly. If tomorrow will be 15°C and sunny, drop the morning target temperature by a degree or two. If a cold snap is coming, start pre-heating earlier. This is the kind of optimization that's impossible with a standalone thermostat.
At bedtime, set the bedroom to your preferred sleeping temperature (most people like 17 to 18°C) and drop everything else to 15°C. In the morning, reverse it: warm up the kitchen and living room, let the bedroom cool down. With TRVs this is trivial. Without them, you're heating your whole house to keep one room comfortable.
Let's do the math. Average Dutch household spends about €1,800 per year on gas (mostly heating). Here's what smart climate control can realistically save.
€180-360
Presence-based heating alone
10-20% savings from not heating when nobody is home
€90-270
Zone control with TRVs
5-15% extra savings from heating only used rooms
€50-100
Window detection + weather adjustments
3-5% from eliminating the dumbest waste
Total realistic savings: €320-730 per year
A Shelly TRV setup for 4 rooms costs about €180. That's a payback period of 3 to 7 months. After that, it's pure savings.
Check Your Current SetupYou don't need to overhaul your entire heating system. Start small, prove the value, then expand.
If you already have a Nest or tado, add it to Home Assistant. Set up presence detection using the companion app on your phone. Create a basic "nobody home" automation. Cost: €0.
Pick your most-used room. Install one TRV and an external temperature sensor. Set up a schedule and a window-open automation. Cost: ~€55.
Add TRVs to 2 to 3 more rooms. Set up the night mode automation. Add window sensors where it matters most (bedrooms, kitchen). Start tracking energy consumption. Cost: ~€130.
Add weather-adaptive heating. Tune your schedules based on actual energy data. Consider replacing your cloud thermostat with a local Shelly relay setup. You're now running a smarter climate system than any off-the-shelf thermostat can deliver.
For full local control, the Shelly TRV is hard to beat. It uses Wi-Fi, integrates natively with Home Assistant, and costs around 45 euros per radiator. For whole-house systems (boiler or heat pump), tado and Nest work through their integrations, though they rely on cloud APIs. If you want 100% local, pair a Shelly 1 relay with a temperature sensor and build your own thermostat logic in Home Assistant.
Yes, but with a catch. Home Assistant can control your Nest through the Google Device Access API, giving you temperature control and scheduling. But this still routes through Google's cloud. For true local control, you'd replace the Nest with a relay-based setup or locally controlled devices like Shelly. Many people keep their Nest for the hardware and layer Home Assistant automations on top.
Most households save 10% to 25% on heating bills with smart thermostat automations. The biggest savings come from presence-based heating, where your system drops to 16 degrees when nobody is home. Zone control with TRVs can push savings to 30% or more, especially when combined with window sensors and weather-adaptive scheduling.
Not necessarily. Start with the rooms you use most: living room, bedroom, home office. Even 3 to 4 TRVs in key rooms give you meaningful zone control and noticeable energy savings. Rooms you rarely use can keep their manual valves turned low. You can always add more later.
A TRV controls one individual radiator. A smart thermostat controls your entire heating system (boiler or heat pump). For the best setup, you want both: a smart thermostat to manage when the boiler fires, and TRVs on individual radiators for room-by-room temperature control. Home Assistant ties them together so the boiler only runs when at least one room actually needs heat.
Run a free scan to see which of your current devices work with Home Assistant, and get a personalized migration plan.
Start Your Free Scan