By Sean Gallagher, Regional Sales Manager Mitsubishi Electric

As temperatures rise and HVAC systems work harder, homeowners often notice rooms that never seem to cool down, utility bills that are higher than expected, persistent humidity and other potential problems.

These complaints can create opportunities for contractors to identify underlying issues, educate homeowners, and recommend solutions that improve long-term comfort and system performance.

Because comfort complaints can stem from many sources, it’s important to look beyond the equipment itself. Airflow, sizing, maintenance, ductwork, the building envelope, and homeowner habits can all play a role. Taking the time to identify the root cause can help reduce callbacks, improve homeowner satisfaction, and build long-term trust.

Key Takeaways<br>

  • Summer’s heavier HVAC usage means more service calls on your schedule.
  • These calls are an opportunity to diagnose the real issue, not just service the equipment – educating homeowners and recommending the right fix builds long-term comfort, performance, and repeat business.
  • Homeowners will describe symptoms, not causes, so your discovery questions upfront do a lot of diagnostic heavy lifting.
  • Identifying the root cause means fewer callbacks and more trust with homeowners.
<a id="hot-cold-rooms"></a>Why are some rooms too hot and others too cold?

Uneven temperatures are among the most common complaints you’ll encounter during the cooling season. While homeowners often assume something is wrong with the HVAC system, the equipment itself is not always the culprit.

Likely causes<br> Many factors can contribute to comfort differences from one room to another:<br>

  • Duct design, airflow distribution, zoning strategy, room orientation, insulation levels, and solar gain all affect how individual spaces feel throughout the day.
  • Homeowner habits can play a role. Closed registers, furniture blocking vents, and rooms isolated from the rest of the home's airflow can create noticeable temperature differences.

Getting to the root of the problem<br> A room that becomes hot and humid in the afternoon may point toward infiltration or building envelope issues. A second story bedroom that never seems quite cool enough may suggest airflow or duct-distribution challenges. Understanding the time of day, outdoor conditions, and location of the complaint helps narrow down the possibilities before diagnostics begin.

When comfort varies from room to room, airflow is often the best place to start. A closer look can reveal whether the duct layout, balancing dampers, or zoning strategy is limiting performance.

Remember that systems are designed around specific outdoor temperature assumptions. During prolonged periods of extreme heat, homeowners may notice temperatures drifting above the thermostat setting even when the system is operating as designed because cooling demands exceed typical design conditions.

If comfort imbalances persist, consider airflow balancing, zoning modifications, or localized comfort solutions such as ductless or multi-zone all-electric, all-climate heat pump systems that provide independent temperature control where it’s needed most.

<a id="high-energy-bill"></a>Why is my energy bill so high?

High energy bills are one of the most difficult complaints to diagnose because perceptions of what constitutes a high bill vary substantially. Utility rates differ widely by region, so it’s important to distinguish between increased energy usage and increased utility costs before focusing exclusively on system performance.

Likely causes<br> In many cases, high cooling costs stem from issues that have developed gradually over time:<br>

  • Dirty coils, clogged filters, duct leakage, refrigerant loss, neglected maintenance, aging equipment, or building envelope deficiencies can all increase runtime and reduce performance.
  • Improperly sized equipment can also contribute to excessive energy consumption, particularly when cooling demands are consistently higher than anticipated.

Steps to diagnose<br> Rather than focusing only on the most recent utility bill, ask the homeowner to consider reviewing year-over-year usage to see when the increase began. If the issue coincides with a renovation, occupancy change, or other home modification, the root cause may extend beyond the HVAC equipment itself. Diagnostic work should confirm airflow, coil and filter condition, refrigerant charge, and whether comfort complaints are concentrated in specific areas of the home.

Proper load calculations are essential to determining whether a system is sized right for the home’s cooling requirements. The Air Conditioning Contractors of America’s (ACCA’s) room-by-room Manual J load calculations are one of the most reliable methods for determining whether a system is appropriately sized. Accurate cooling load calculations account for the home’s insulation levels, window performance, orientation, room usage patterns and overall square footage.

When equipment is nearing the end of its service life or is found to be improperly sized, you can discuss replacement options. A system upgrade to a modern, inverter-driven heat pump, which is designed to match capacity to demand, may be recommended.

<a id="ac-always-running"></a>My AC is always running, why is it still hot inside my house?

Homeowners may become concerned when a system appears to be running nonstop without delivering the desired temperature. However, continuous operation doesn’t always indicate equipment failure.

Likely causes<br>

  • Dirty or blocked coils
  • Insufficient maintenance
  • Refrigerant leaks
  • Airflow restrictions
  • Poor insulation
  • Air leakage
  • Excessive solar gain
  • Thermostat location issues
  • Undersized equipment

Thermostat placement can sometimes influence runtime as well, particularly when the thermostat is exposed to unusual heat loads or does not accurately reflect conditions throughout the home.

Airflow restrictions are often overlooked but can significantly impact performance. Closed doors, blocked returns, and restricted return-air pathways can prevent the system from distributing air as designed.

Rather than cycling on and off repeatedly, many variable-capacity systems operate for extended periods at lower output levels to maintain a more consistent indoor environment. As a result, longer runtimes may be normal depending on conditions and system design.

When investigating runtime complaints, a few core diagnostics remain essential:<br>

  • Verify runtime patterns and thermostat operation.
  • Measure supply and return air temperatures.
  • Confirm airflow and refrigerant charge.
  • Inspect coils, filters, and potential airflow restrictions.
  • Evaluate insulation and air leakage conditions.

Regular maintenance should also be part of the discussion because it’s one of the simplest ways to identify developing issues before they lead to larger comfort concerns or service calls.

<a id="humid-home"></a>Why does it always feel humid in my home?

Even when a home reaches the desired thermostat setting, high humidity can make it feel uncomfortable.

Likely causes<br>

  • In many cases, excessive humidity stems from oversized equipment that satisfies temperature demands too quickly and doesn’t operate long enough to support moisture removal.
  • Infiltration, duct leakage, fresh-air imbalances, crawl-space conditions, and short cycling can contribute as well.

Digging deeper<br> Measuring indoor relative humidity and reviewing system runtime patterns can reveal whether the issue is tied to equipment operation or building performance. Reviewing equipment sizing can also help determine whether the system is operating long enough to support effective moisture removal.

Air leakage around windows, doors, and other components of the building envelope can also introduce substantial moisture into the home. Likewise, duct leakage and ventilation imbalances can undermine comfort even when cooling performance appears satisfactory. Addressing infiltration and airflow issues may have as much impact as equipment-related adjustments.

<a id="ac-weird-noises"></a>Why is my AC making weird noises?

While some noises can indicate developing mechanical issues, others are part of normal operation.

Likely causes<br>

  • Loose blower wheels
  • Fan motor issues
  • Compressor wear
  • Refrigerant flow sounds
  • Duct vibration
  • Cabinet vibration
  • Mounting concerns

Begin troubleshooting with a simple question: is the sound coming from indoors, outdoors, or within the duct system?

The timing of the sound can also provide important clues. Noises that occur only during startup may point toward different causes than noises that occur during continuous operation. Understanding when the sound occurs helps guide the diagnostic process and prevents unnecessary guesswork.

Not every sound should be interpreted as a problem. In some ductless systems, for example, indoor units may emit a crackling sound as the front panel expands and contracts during large temperature changes.

Still, any new, worsening, or persistent sound should be investigated to confirm the system is operating as intended. Check out this video from Mitsubishi Electric Trane HVAC US (METUS) to learn more about common noises and what to do about them.

<a id="turning-complaints-into-opportunities"></a>Turning Complaints into Opportunities

The most successful contractors understand that summer comfort complaints are rarely about a single component.

When you pair thorough discovery with a whole-home view of comfort, you can set clearer expectations and move beyond symptom-based repairs toward more effective long-term solutions. Taking the time to explain what is happening and recommend the right path forward builds homeowner confidence, strengthens trust, and helps position you as a reliable partner for future comfort needs.

Sean Gallagher, Regional Sales Manager Mitsubishi Electric

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Sean Gallagher is a Regional Sales Manager for Mitsubishi Electric Trane HVAC LLC serving Western Massachusetts and Vermont markets with specialties in Sales, HVAC Product Application and Contractor Development. Sean has served the HVAC Industry for the last 25 plus years in roles ranging from HVAC Sales, Technical Training and HVAC Education. He is passionate about the HVAC field and heavily involved in providing training and customer service to HVAC contractors with focus on the Northeast region.