How to Test the Efficiency of Your Central Air Conditioner Before Summer
As temperatures begin to rise, ensuring your central air conditioning (AC) unit is working efficiently becomes essential. The best time to check the performance of your AC system is before the summer season arrives. After all, there’s nothing more frustrating than having a central AC unit that doesn’t cool your entire home effectively when you need it the most.
While doing a DIY test can feel overwhelming, especially if you're not familiar with the procedure, following a few simple steps can help. Alternatively, you can always call a professional for heating and air conditioning in Roanoke, VA to assess the system for you. Here’s a comprehensive guide to help you determine if your central air conditioner is operating efficiently.
Why AC Efficiency Matters
A central AC system that runs inefficiently not only makes your home uncomfortable but also leads to higher energy bills and unnecessary wear and tear on the system. By testing your AC before peak usage, you can avoid last-minute breakdowns and ensure your home stays cool throughout the summer.
What You’ll Need
To test your central air conditioning system, you’ll need:
- A reliable household thermometer
- Tissue paper (optional but helpful)
- Access to indoor air ducts and the outdoor AC unit
Before you begin, consider removing the air filters so they don’t obstruct airflow during testing. Dirty filters can give you misleading results.

Step-by-Step Guide to Test Your AC's Cooling Efficiency
Step 1: Turn On Your AC Unit
Start by switching on your AC unit during a warm day, as this will provide the most accurate test conditions. Set the thermostat well below the current room temperature to ensure the unit kicks on. Let it run for 15–20 minutes so that the system stabilizes before conducting any measurements.
Step 2: Locate the Air Ducts
Identify the supply and return air ducts in your home. Here's an easy trick using a tissue paper:
- Hold the tissue over the duct.
- If the tissue gets sucked in, it’s a return duct.
- If it blows away, it’s a supply duct.
This step is crucial, as you’ll need to measure temperatures at both locations.
Step 3: Check the Airflow
Next, check if cool air is coming out of the supply vents. You should feel a noticeable cold breeze. If the airflow seems weak or uneven, inspect your air filters. Clogged or dirty filters are often the culprit behind poor airflow. If you've already removed the filters and airflow is still restricted, there might be a deeper issue within the ductwork.
In such cases, it’s best to contact an HVAC specialist for a professional inspection.
Step 4: Clean Around the Outdoor Unit
Don’t overlook the outdoor unit. Ensure the area around it is clear of debris such as leaves, dirt, or twigs. Any blockage can disrupt airflow and reduce the unit’s ability to cool efficiently. Regularly cleaning around this unit helps maintain proper function and extends the life of your system.
Step 5: Measure the Temperatures
Now comes the most telling part of the test measuring the temperature difference between the return and supply air.
- Place a thermometer near the return duct and leave it there for about five minutes. Record the reading.
- Then, place the thermometer at the supply duct and wait for another five minutes.
Compare the two readings. Ideally, the air coming from the supply duct should be 15 to 20 degrees cooler than the air entering through the return. If this is the case, your AC unit is performing efficiently.
If the difference is less than 15 degrees, it could indicate one of the following issues:
- Low refrigerant levels
- Dirty or blocked air filters
- Problems within the compressor or evaporator coil
When to Call a Professional
Testing your central air conditioner at home can give you a rough idea of its efficiency. However, if your system doesn’t meet the ideal temperature differential, or if you're unsure about the results, it’s time to call in the experts.
For reliable air conditioning services in Roanoke, VA, look no further than The Woods Family HVAC. Our experienced technicians can diagnose and fix efficiency issues, ensuring your system is ready for the summer heat.
Contact The Woods Family HVAC Today
Don’t wait until the hottest day of the year to find out your AC isn’t working. Ensure peace of mind by scheduling a professional check-up.
Stay cool, comfortable, and energy-efficient all summer long!