How is luminaire efficiency defined, and are there any rules?
Luminaire efficiency is measured in lumens per watt (Lm/W) and shows how effectively a luminaire converts electrical energy into visible light. It plays a key role in sustainable lighting design—but it’s never the only factor. Lighting performance should always be evaluated in conjunction with beam control, visual comfort, and the intended atmosphere.
System efficiency vs light source efficiency
A common point of confusion is the distinction between light source efficiency and system (or luminaire) efficiency. LED chips can reach 160–200Lm/W in laboratory conditions. This is their chip-level performance. However, once installed in a real luminaire—with optics, housing, and thermal protection—the actual output is lower. This is the system efficiency, and it reflects the performance you experience on site.
At Karizma Luce, we always publish the system Lm/W for each version in the product datasheet. That includes optical losses, housing effects, and thermal behaviour. Comparing luminaires based on chip data alone can lead to false assumptions. Always check the manufacturer’s datasheet to get accurate, real-world values.
What influences system efficiency?
Several factors affect the final system efficiency:
- Optics – Lenses, diffusers, and reflectors absorb a portion of the light to reduce glare or shape the beam.
- Housing – Material, colour, and internal reflectivity impact the amount of light emitted.
- Thermal design – Stable heat management ensures consistent LED output and prolongs lifespan.
- CCT (colour temperature) – Cooler tones (e.g. 4000K) usually offer slightly higher efficiency than warmer ones.
- CRI (colour rendering index) – High CRI improves colour quality but can slightly reduce output.
Are there any rules or thresholds?
While there’s no universal minimum for luminaire efficiency, some regulations and guidelines apply:
- The EU Ecodesign Directive sets minimum efficacy for light sources and some integrated luminaires.
- LEED or BREEAM certifications often require general lighting to exceed 100Lm/W.
- Spaces focused on ambience or high CRI—such as museums or restaurants—may accept lower values (around 80–90 Lm/w).
Profondo Basso Swing as an example
A well-designed architectural luminaire typically achieves a luminous efficacy of between 80 and 120 Lm/W. The deeply recessed reflector in Profondo Basso Swing ensures excellent glare control while maintaining high performance. The 4000K version delivers up to 104Lm/W—a strong balance of efficiency and visual comfort for architectural interiors.
Need a high-efficiency solution?
At Karizma Luce, we prioritise absolute, delivered or real values. Our datasheets include both system efficiency and luminous flux, version by version. The most efficient luminaires from Karizma Luse include downlights from the Casa family, like Casa M Alto, or track spot Caro—each designed for strong output with elegant integration.
Are you unsure which luminaire best suits your concept? Feel free to contact us—we’ll help you find the most efficient and refined option for your space.
