🏠 In brief: Smart heating control is the easiest entry point for energy savings — especially in older buildings. Programmable thermostats cost €30–80 per radiator, save 10–15% heating energy, and pay for themselves in 1–2 heating seasons. No tradesperson needed, no structural work required.
Save Energy Without Major Renovation
Not everyone can or wants to tackle a comprehensive renovation right away. Whether it is a rental apartment, a limited budget, or missing permits — the entry into energy saving often fails due to the high barriers of traditional measures like insulation or heating replacement.
This is exactly where smart home technology comes in. Smart thermostats and sensors can be installed in minutes, require no tradesperson, and can noticeably reduce energy consumption — entirely without structural modifications.
The advantage: You can start immediately, the costs are manageable, and the savings are measurable. Below, we show which systems make sense, what they cost, and where the limits are.
Smart Thermostats: The Easiest Entry Point
The old thermostatic valve on the radiator only knows one setting: the one you last selected. A smart thermostat, on the other hand, automatically regulates room temperature on a schedule, detects open windows, and can be controlled remotely via app.
What Smart Thermostats Can Do
Scheduling: Program heating times — lower at night, heat during the day, frost protection during holidays.
Geofencing: The thermostat detects via your smartphone whether you are home and automatically lowers the temperature when you leave.
Room-by-room control: Each room gets the temperature it needs — 20 °C in the living room, 17 °C in the bedroom, 22 °C in the bathroom.
Open window detection: When temperature drops suddenly, the thermostat automatically stops heating.
💰 Cost & savings:
- Purchase price: €30–80 per radiator (depending on manufacturer and feature set)
- Typical savings: 10–15% of heating costs
- Popular systems: tado°, Homematic IP, Eve Thermo, AVM FRITZ!DECT
- Installation: Unscrew old thermostat, screw on new one — tool-free in 5 minutes
Smart Heating Control in Old Buildings
Many owners of older buildings believe that smart home technology only works in new builds. The opposite is true: especially in older buildings, the savings potential is particularly high because heating is often regulated inefficiently.
Modern retrofit solutions use wireless instead of wiring. The smart thermostats communicate via Zigbee, Thread, or Wi-Fi with a central gateway, which in turn can be connected to your existing gas or oil boiler.
Advantages in Old Buildings
Wireless: No cables to run, no plaster to break open — purely wireless.
Compatible: Works with existing gas, oil, and pellet heating systems via gateways like tado° or Homematic IP.
Weather-based control: The system considers outdoor temperature and automatically adjusts the flow temperature — similar to weather-compensated control.
Tenant-friendly: When moving out, simply screw the old thermostats back on.
Window Contacts and Presence Sensors
We all know the situation: the window is open for ventilation, but the heating continues running at full power. Window contacts solve exactly this problem. They notify the system when a window is opened, and the thermostat immediately turns down the heating.
Presence sensors go one step further: they detect whether someone is in the room. If the room is unused for a longer period, the temperature is automatically lowered. When someone enters again, the system heats up in time.
💡 Practical tip: Window contacts cost from approx. €10–25 each and deliver an additional 5–8% savings because heating against open windows is reliably prevented. Especially useful in households with children or pets.
Energy Monitoring: Making Consumption Visible
What you cannot measure, you cannot improve. That is exactly why energy monitoring is an important building block of smart energy saving. Modern smart meter gateways and consumption apps show in real time how much electricity and heat your household consumes.
Studies show: simply being aware of your own consumption leads to a reduction of 5–10%. When you see how much the constant hot water circulation costs or how high the consumption of the guest room is, you act on your own.
Typical Energy Wasters That Become Visible
• Heating runs at full power in unused rooms
• Hot water circulation pump runs around the clock (instead of on demand)
• Nighttime heating with open windows
• Old circulation pump consumes 80–120 W instead of 5–15 W (high-efficiency pump)
What Does It Really Save? A Calculation Example
How much does smart home heating control actually save? We calculate with a typical single-family home in the Siegerland region:
Starting situation:
Single-family home, built 1978, gas heating, 150 m² living area
Annual consumption: approx. 20,000 kWh gas (≈ €2,400 at 12 ct/kWh)
Investment:
10 smart thermostats at €50 each = €500
4 window contacts at €20 each = €80
Gateway/bridge: €80
Total investment: approx. €660
Savings:
Conservative 10%: 2,000 kWh/year → €240/year
Optimistic 20% (with monitoring and behavior change): 4,000 kWh/year → €480/year
Payback period: 1.5–3 years — after that, you save real money year after year.
⚡ Important: The greatest savings come from the combination of technology and behavior. If you install smart thermostats but never set up the schedules, you are wasting potential.
Limits of Smart Home
As useful as smart heating control is — it has clear limits. If the building is poorly insulated and heat escapes through the roof and walls, even the cleverest thermostat can only help to a limited extent.
Smart home does not replace insulation, heating replacement, or hydraulic balancing. It is one building block — not a substitute for an energy retrofit. The most effective approach is the combination: first improve the building envelope, then optimize the heating, and use smart controls to squeeze out the last savings.
Smart home alone is not enough when…
• The exterior walls and roof are uninsulated (U-value > 1.0 W/m²K)
• Single glazing is present (U-value > 3.0 W/m²K)
• The heating system is over 25 years old and operates inefficiently
• No hydraulic balancing has been performed
Our advice: Use smart home as an immediate starting point. In parallel, plan the next steps with an energy consultant — e.g., with an individual renovation roadmap (iSFP) that prioritizes all measures and identifies funding opportunities.
Note: All figures are as of July 2026. Prices and products may change. This article does not replace individual consulting.
Save Energy — Step by Step
Want to know which measures bring the most benefit for your building? We advise you — from smart home to complete renovation.