What Electrical Thermal Imaging Can and Cannot Detect

Thermal imaging has become a popular add-on for electrical inspections, and for good reason — an infrared camera can spot a failing connection before it turns into smoke. But it also gets oversold. Too many people treat a thermal scan like an X-ray that reveals everything hiding in the walls. It doesn't. Here's an honest look at what the technology actually does, where it shines, and where its limits are — from an electrician who uses it as one tool among several.

How Infrared Cameras Find Electrical Problems

Every electrical connection has a small amount of resistance. When a connection is tight and clean, that resistance is negligible and the connection stays cool. When a connection loosens, corrodes, or is asked to carry more current than it should, resistance climbs — and resistance under current produces heat. That heat is the fingerprint an infrared camera is looking for.

A thermal camera doesn't take an ordinary photo. It reads the infrared energy radiating off a surface and translates temperature differences into a color image. On a healthy panel, the breakers and terminals sit at roughly the same temperature. When one breaker or one lug glows noticeably hotter than its neighbours carrying similar load, that's a red flag worth investigating with your hands and eyes.

In a residential setting, the most useful places to point the camera are the main panel and any subpanels, plus larger dedicated loads — electric baseboard or furnace circuits, an EV charger, a hot tub feed, or a workshop. These carry enough current for a bad connection to reveal itself. For more on what those breakers and lugs actually are, our guide on how to read your electrical panel is a good primer.

What Thermal Imaging Is Genuinely Good At

• Catching loose terminations. A backed-out lug or a breaker that isn't fully seated heats up under load. Thermal imaging spots this before it arcs or melts insulation.
• Finding overloaded circuits. A breaker or conductor running consistently hot compared to its neighbours can indicate a circuit carrying more than it should.
• Screening panels quickly. In a few minutes an electrician can survey an entire panel and flag the one connection that needs a closer look.
• Non-destructive checks. Nothing is torn open or dismantled. The camera reads surfaces, so it's a low-impact way to add information to an assessment.
• Documenting a baseline. A dated thermal image gives you a record of panel condition at a point in time — useful for property files and follow-up scans.

What Thermal Imaging Cannot Do

This is where honesty matters, because the marketing around infrared can get out of hand. Here's what the camera genuinely cannot tell you.

It cannot see through walls. Infrared reads the temperature of a surface — the outermost layer facing the camera. Drywall, plaster, and the steel cover of a panel all block the view of what's behind them. If a junction box is buried inside a finished wall with a loose connection that isn't drawing enough current to heat the wall surface, the camera won't see it. This is the single biggest misconception about the technology. It is not an X-ray.

It cannot judge the condition of concealed wiring. In older Toronto homes with knob-and-tube or early cloth-insulated wiring hidden in walls and ceilings, a thermal scan of the panel tells you nothing about the state of the conductors running through the house. The only way to assess concealed wiring is direct access — opening boxes, pulling devices, or opening finishes. If knob-and-tube is a concern, that's a hands-on job; see our guides on whether knob-and-tube is dangerous and knob-and-tube rewiring.

It cannot guarantee there are no faults. A thermal scan is a snapshot in time under the load that happens to be present. A loose connection on a circuit that wasn't energized — or was barely loaded — during the scan can read stone cold. Come back on a winter evening with the electric heat running and that same connection might light up. A clean scan means "nothing was hot right now," not "everything is perfect."

It doesn't diagnose on its own. A hot spot is a clue, not a verdict. Some heat is normal — a breaker fully loaded to near its rating will run warm, and that can be fine. Interpreting the image takes an electrician who understands the load, the equipment, and the code. Without that judgment, thermal images produce false alarms and false comfort in equal measure.

Why Load Is Everything

The most important thing to understand about thermal imaging is that no load means no heat. Heat at a bad connection is generated by current flowing through resistance. Turn the current off and the connection cools right back down, hiding the fault.

A good electrician will try to get meaningful load onto the system before scanning — running the dryer, the range, the electric heat, or whatever draws real current — so that the panel is working when the camera comes out. Even then, some circuits simply aren't in use during a daytime visit, and those readings will be incomplete. This is one reason a single thermal scan is a screening step, not a certification.

Where Thermal Imaging Fits in a Real Inspection

Thermal imaging is at its best as one part of a broader assessment, not a service on its own. During a Portman Electric electrical safety inspection, an electrician visually checks the visible and accessible components — panel, terminations, grounding and bonding, device condition, and code concerns — and produces a written report. Adding a thermal scan of the panel and major loads sharpens that assessment by pointing to connections that are running hot right now.

Keep this straight, though: a Portman contractor assessment — with or without thermal imaging — is not an ESA inspection. Our assessment looks at what's visible and accessible and hands you a written report of findings. An ESA inspection is a review of permitted work under provincial authority, and ESA — not us — issues the Certificate of Acceptance. A non-destructive assessment, thermal camera or not, can't see concealed wiring behind finished walls. Both have their place; they answer different questions.

For property managers and landlords maintaining multiple units, periodic thermal scans of panels can be a smart, low-disruption way to catch developing problems in occupied suites — something we cover as part of property management electrical work. And if a hot connection is found and something is already failing, that can turn into an emergency call — better to find it on a scan than at 2 a.m.

Is It Worth Paying For?

For a lightly loaded condo or a small, newer home, a thermal scan often finds nothing — which is genuine, if modest, reassurance. For an older home, a heavily used panel, a property with add-on circuits over the years, or larger loads like EV charging and electric heat, the odds of catching a developing hot spot go up, and the modest cost of adding a scan can be well spent. The honest answer is that its value scales with how much current your system actually carries and how many connections have been made and remade over the decades.

Just don't buy it as a magic wand. Used well, by someone who understands its limits, thermal imaging is a useful early-warning tool. Used as a substitute for a real hands-on inspection — or sold as proof your wiring is flawless — it will mislead you. If you want it done right, ask for it as part of a full assessment, not instead of one.

Common Questions About Thermal Imaging