Thermal camera apps and clip-on smartphone thermal attachments can be a handy first step for spotting obvious heat distribution issues around your home, but they won't give you a full picture of your heat pump's health. For a proper performance assessment, you'll still need a qualified heat pump technician — but understanding what these tools can and can't do will help you make smarter decisions.
What Thermal Camera Apps Actually Are
There are two types of tools often called "thermal camera apps":
- Smartphone thermal attachments — small hardware devices (such as those made by FLIR or Seek Thermal) that plug into your phone and use a real infrared sensor. These produce genuine thermal images.
- Software-only "thermal" apps — these use your phone's regular camera and apply a colour filter. They do not detect heat and are essentially useless for any real diagnostic work.
If you're serious about doing a DIY thermal check, you need the hardware attachment version. Expect to pay anywhere from a few hundred dollars upward as a rough guide — or consider hiring one from a tool library or equipment hire shop.
What You Can Realistically Check
With a genuine thermal attachment, a homeowner can spot some useful things around their heat pump system:
- Air distribution — you can see whether warm or cool air is actually reaching different parts of the room by scanning walls, floors, and ceiling areas near vents.
- Obvious blockages or dirty filters — a clogged filter often shows as uneven temperature patterns across the indoor unit's face.
- Insulation gaps — thermal imaging is well-known for revealing where heat is escaping through walls, ceilings, or around windows, which directly affects how hard your heat pump has to work. BRANZ has good guidance on building envelope performance.
- Outdoor unit frost or ice build-up — visible as cold patches on the unit during winter operation.
What Thermal Imaging Cannot Tell You
This is where homeowners need to be realistic. A thermal camera — even a professional-grade one — cannot:
- Measure refrigerant charge — low refrigerant is one of the most common causes of poor heat pump performance, and it requires specialist gauges and a licensed technician to diagnose and fix.
- Check electrical components safely — while thermal imaging is used professionally to spot hot electrical connections, poking a camera around electrical panels yourself carries real risk. See WorkSafe NZ for guidance on electrical safety.
- Read compressor health or efficiency ratings — these require specialised diagnostic equipment.
- Measure airflow volume (CFM) — thermal images show temperature, not how much air is actually moving.
- Identify refrigerant leaks — leaks need electronic leak detectors or UV dye testing by a professional.
| What thermal imaging can show | What it cannot show |
|---|---|
| Surface temperature patterns | Refrigerant charge level |
| Insulation gaps in walls/ceiling | Compressor efficiency |
| Uneven airflow distribution | Electrical fault diagnosis |
| Ice or frost on outdoor unit | Airflow volume |
| Dirty or blocked filters (roughly) | Refrigerant leaks |
Tips for Getting the Most from a DIY Thermal Check
- Check at the right time — run your heat pump for at least 15–20 minutes before scanning so temperatures have stabilised.
- Mind the ambient temperature — thermal cameras work best when there's a meaningful temperature difference between surfaces. A warm day makes spotting cool air leaks harder.
- Clean your filters first — manufacturer guidelines generally recommend cleaning filters every few weeks during heavy use. A clean filter gives you a better baseline reading.
- Don't scan directly into the sun — reflected solar radiation throws off readings on outdoor units.
- Document what you find — take screenshots and note the date and conditions. This is useful context if you later call a technician.
NZ Building Code and Healthy Homes Context
If you're a landlord, the Healthy Homes Standards require adequate heating in rental properties. A thermal camera check won't satisfy compliance requirements, but it can help you identify whether your heat pump is actually heating the main living area effectively before an official assessment. For compliance questions, check with MBIE Building Performance.
When to Call a Professional
Call a qualified heat pump installer or refrigeration technician if you notice any of the following:
- The unit is running but the room isn't reaching the set temperature
- You can hear unusual noises (grinding, hissing, or rattling)
- The outdoor unit is icing up heavily and not defrosting
- Your power bills have increased significantly without a change in usage
- The unit is more than 5–8 years old and hasn't had a service
Important: Any work involving the refrigerant circuit — including recharging, leak testing, or component replacement — is restricted work in New Zealand and must be carried out by a licensed refrigeration technician. This is not a DIY job, regardless of what you find with a thermal camera.
You can find qualified heat pump installers and refrigeration technicians in your area at tradedirectory.co.nz.
ISO 9001
