Understanding the Thermal Reality Behind Every Watt
In commercial refrigerated display cases, lighting is often discussed in terms of brightness, color rendering, or merchandising impact. Yet from an engineering perspective, lighting plays a far more critical role — it directly influences the refrigeration system’s thermal load.
For OEM manufacturers, refrigeration engineers, and system designers, one fact remains fundamental:
Every watt of lighting installed inside a refrigerated display case becomes heat that must be removed by the refrigeration system.
This is not a marketing interpretation. It is basic thermodynamics — and it directly affects compressor sizing, energy consumption, temperature stability, and long-term system efficiency.
1. Lighting Inside the Cooling Boundary: Why It Matters
In a supermarket environment, ceiling lights illuminate from outside the refrigeration envelope. Their heat dissipates into ambient store air.
But refrigerated display lighting is different.
LED modules, drivers, brackets, and lenses are installed inside the insulated cabinet — within the defined cooling boundary. That means:
- Electrical power enters the refrigerated space
- Nearly all of it converts to thermal energy
- That heat must be continuously extracted
From a physics standpoint:
Electrical energy → Thermal energy → Refrigeration removal
There is no “free” watt inside a refrigerated case.
2. The Thermodynamic Relationship
The relationship is straightforward:
Where:
- Q = Heat added to refrigerated space (W)
- P = Electrical input power of lighting system (W)
En pratique, 95–100% of LED lighting power becomes heat inside the cabinet, depending on:
- Driver location (internal vs external)
- Heat sink efficiency
- Optical design
- Airflow management
Even highly efficient LEDs (160 lm/W or higher) still convert the majority of input power into heat. Luminous efficiency improves visual output — but it does not eliminate thermal load.
This is why lighting design is inseparable from refrigeration design.
3. What This Means for OEM Manufacturers
For showcase manufacturers, lighting power influences:
- Compressor runtime
- Evaporator load
- Defrost frequency
- Cabinet pull-down time
- Temperature fluctuation near product surfaces
A difference of 20–40 watts per cabinet may appear small — but across:
- 50 cases in a supermarket
- 500 cases in a hypermarket chain
- Thousands of units across a brand rollout
The cumulative refrigeration burden becomes significant.
This is why leading OEMs increasingly evaluate lighting not just by brightness — but by thermal contribution per linear meter.
4. Practical Engineering Example
Consider a vertical multi-deck glass door freezer:
| Item | Case A | Case B |
|---|---|---|
| Lighting Power | 60 W | 35 W |
| Daily Heat Added | 1.44 kWh | 0.84 kWh |
| Annual Heat Load | 525 kWh | 307 kWh |
That 25 W reduction saves over 200 kWh per case annually in refrigeration removal.
Multiply this across an installation of 200 cases, and the energy difference becomes operationally meaningful.
5. Beyond Wattage: Thermal Distribution Matters
Not all lighting systems transfer heat the same way.
Key factors include:
- Lens angle and optical control
- Surface-mount vs recessed design
- Aluminum profile heat dissipation
- Driver separation
- Placement relative to airflow channels
De Laidishine, lighting systems are designed specifically for refrigerated environments — not adapted from general retail fixtures.
Par exemple:
- Our SPU series is engineered with optimized thermal paths
- DC24V systems reduce internal driver heat
- IP65 sealing maintains thermal stability in humid environments
- Optical control minimizes unnecessary radiant heating toward products
The goal is not only lower wattage — but controlled heat behavior.
6. Why This Is Becoming More Important
Aujourd'hui, retailers and OEM partners are under increasing pressure to:
- Meet energy regulations (DOE, EU Ecodesign)
- Improve ESG performance
- Reduce compressor cycling
- Maintain consistent food temperature
Lighting can either support these objectives — or silently undermine them.
Forward-thinking manufacturers now treat lighting as a refrigeration component, not a decorative accessory.
7. The Strategic Takeaway
For refrigerated display case OEMs:
- Every lighting watt must be included in refrigeration load calculations
- Lower connected power reduces compressor demand
- Proper optical and thermal design protects temperature stability
- Lighting decisions impact long-term energy performance
De Laidishine, we collaborate with refrigeration engineers early in cabinet development to ensure lighting integrates thermally, mechanically, and optically — without adding unnecessary load.
Because in refrigeration design, every watt matters.
