Is It Better to Use My Thermal Imaging Camera at Night?
A common question we hear is:
“Should I use my thermal imaging camera at night for better results?”
While time of day does influence the outcome, it’s not the only — or even the most important — factor. The answer lies in understanding the application, the load conditions, the environment, and just as critically, the skill and competence of the thermographer.
Load Is the Most Important Factor
For thermal inspections — especially electrical — load is king.
Whether you’re inspecting transformers, isolators, conductors, or insulators on high-voltage overhead systems, or doing lower-voltage switchgear surveys, the presence of electrical load is what causes heat buildup at points of resistance or stress.
No load = No heat = No problem detected.
If overhead lines or substations are operating under minimal or no load, even major faults can go unnoticed.
Day vs. Night: Environmental Influences
For outdoor high-voltage equipment, environmental factors play a significant role. These include:
🔆 During the Day:
- Solar loading can heat up equipment surfaces, potentially masking true hot spots or creating false ones.
- Reflections from sunlight or surrounding objects can distort readings — especially on shiny metallic surfaces.
- Wind and weather can affect how heat is distributed or dissipated, especially at height.
🌙 At Night:
- Solar influence is eliminated, resulting in more accurate temperature differentiation.
- The background (ambient) temperature is often lower, which can enhance thermal contrast.
- However, cold wind or rapid nighttime cooling can reduce visibility of marginal faults, especially if equipment cools too quickly.
For this reason, early morning or just after sunset is often ideal, offering a balance between active load and reduced solar effects.
Competence Matters: Training and Skill Are Critical
Thermal imaging is not a "point-and-shoot" technology. While modern cameras are powerful, the accuracy of any inspection still depends on the skill, experience, and training of the thermographer.
A professional thermographer must:
- Understand emissivity, reflected apparent temperature, and atmospheric transmission loss
- Know how to interpret thermal patterns and rule out environmental effects
- Recognize true anomalies versus artifacts caused by sunlight, wind, or cold atmosphere
- Know when to apply load measurements and use complementary diagnostic tools
A poorly trained operator can easily misread data or overlook serious faults — which can lead to costly equipment failure or safety hazards.
So, When Is the Best Time to Perform a Thermal Inspection?
✅ For high-voltage outdoor electrical systems:
- Aim for early morning or evening, when solar loading is minimal but the equipment is still under operational load.
- Avoid midday inspections unless absolutely necessary, or unless the thermographer is highly experienced in compensating for solar influence.
✅ For indoor equipment:
- Any time is possible, as long as the load is present — though avoiding direct sun exposure from windows is still advised.
✅ For mechanical or building inspections:
- Choose a time based on equipment runtime or thermal cycles — not just the clock.
Final Thoughts
While using a thermal imaging camera at night may seem like a logical choice to avoid sunlight interference, it’s not a guaranteed recipe for success. The best results come from:
- Understanding the application
- Timing the inspection with active load
- Being aware of environmental influences
- And most importantly, having a properly trained and certified thermographer on-site
Because in thermography, it’s not just about when you inspect
— it’s about how well you understand what you're looking at.