Energy Savings with KNX: How a Villa Reduced Its Consumption by 40%
Detailed case study of a 200m² villa in Luxembourg: energy monitoring, sub-metering per circuit, before/after audit and concrete results. Discover how KNX saved 4,800 kWh per year.
Key Results of the Study
Project Context
This case study presents the concrete results of a KNX installation in a 200m² villa located in Strassen (Luxembourg). The owner wanted to reduce their energy bill while improving daily comfort.
Home Characteristics
Building
- • Living area: 200m²
- • Construction: 2005
- • Insulation: Standard RT2005
- • Number of rooms: 8
Existing Equipment
- • Heating: Air/water heat pump
- • DHW: Thermodynamic cylinder
- • Lighting: LED + halogen
- • Blinds: motorised but not automated
Initial Energy Audit
Before the KNX installation, we conducted a complete energy audit with temporary sub-meters installed for 3 months to establish a precise reference baseline.
Consumption Before KNX
Annual Consumption Breakdown: 12,000 kWh
| Item | kWh/year | Share |
|---|---|---|
| Heating/Air conditioning | 5,400 | 45% |
| Domestic hot water | 2,400 | 20% |
| Lighting | 1,800 | 15% |
| Appliances | 1,440 | 12% |
| Standby and misc. | 960 | 8% |
KNX Installation Carried Out
Installed Components
8 thermal zones with sensors
24 circuits with dimming and presence
12 blinds with solar scenarios
6 permanent KNX sub-meters
Automatic adaptation to conditions
Detectors + smartphone geolocation
Installation Budget
Investment Details
- • KNX equipment: €8,500
- • Energy sub-meters: €1,200
- • Installation and cabling: €3,800
- • ETS programming: €2,500
- • Total: €16,000
Results After 18 Months
Savings by Consumption Item
| Item | Before | After | Savings |
|---|---|---|---|
| Heating/AC | 5,400 kWh | 3,510 kWh | -35% |
| Lighting | 1,800 kWh | 720 kWh | -60% |
| Standby/misc. | 960 kWh | 192 kWh | -80% |
| DHW | 2,400 kWh | 2,160 kWh | -10% |
| Appliances | 1,440 kWh | 1,368 kWh | -5% |
| TOTAL | 12,000 kWh | 7,200 kWh | -40% |
Gain Analysis by Feature
Heating (-35%)
- • Zoning: -15% (unoccupied rooms)
- • Scheduling: -10% (night/absence)
- • Solar blinds: -7% (free solar gains)
- • Open windows: -3% (auto cut-off)
Lighting (-60%)
- • Presence detection: -30% (auto switch-off)
- • Dimming: -15% (adapted light)
- • Natural light: -10% (lux sensor)
- • Scenarios: -5% (all off)
Return on Investment Calculation
Detailed ROI
Note: With energy price increases (+15% in 2023), the real ROI could drop to 3.5 years.
Monitoring and Continuous Follow-up
The installation includes a permanent energy monitoring system that enables the owner to:
- Visualise real-time consumption per circuit
- Compare consumption month by month, year by year
- Detect anomalies (unusual overconsumption)
- Optimise behaviour via personalised alerts
Frequently Asked Questions (FAQ)
What energy savings can you realistically expect with KNX?
Savings vary from 25% to 45% depending on configuration. Our case study demonstrates a 40% reduction on a 200m² villa, around 4,800 kWh/year saved.
What is the return on investment of a KNX installation?
Typical ROI is 3 to 6 years depending on installation size and energy rates. Our case study shows a 4.2-year ROI with 2023 Luxembourg rates.
How does KNX enable consumption monitoring?
KNX integrates electrical sub-meters per circuit, power sensors and supervision interfaces that enable real-time monitoring and detailed history.
Which consumption items are most impacted by KNX?
Lighting (-60%), heating (-35%) and electrical standby (-80%) are the items where KNX generates the most savings thanks to intelligent automation.
Conclusion
This case study concretely demonstrates the savings potential of a well-designed KNX installation. With a 40% reduction in energy consumption and a 4.2-year ROI, investing in KNX smart home is not only profitable but also beneficial for the environment.
Assess your savings potential
Our experts carry out a free energy audit of your home to estimate your potential savings with KNX.
Request a free auditAbout the author
Sophie Klein
Energy and KNX expert
Specialist in energy audits and optimisation of KNX installations. Sophie has carried out more than 100 audits in Luxembourg.
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