What’s Really Going On With Your Air Conditioner?

This might surprise some people, but your air conditioner doesn’t actually make cold air.

What it does is remove heat from inside your home and move that heat outdoors. It accomplishes this by circulating refrigerant through the system. As the refrigerant changes from a liquid to a vapor and back again, it absorbs heat from inside your home and releases it outside.

Here’s something many homeowners don’t realize.

Turning your thermostat from 75°F down to 68°F doesn’t make the air coming out of your vents any colder.

It simply tells the system to run longer in an attempt to reach that temperature. On extremely hot days, it may never get there because your system is only capable of moving so much heat every hour.

A properly operating system usually produces about a 15-20°F temperature drop across the indoor coil. If the air entering your return is 75°F, you can expect the supply air to be somewhere around 55-60°F under normal conditions.

Every air conditioner also has limits. There is only so much refrigerant circulating through the system, and it can only absorb and reject a certain amount of heat each cycle. Once the system reaches its capacity, asking for a lower thermostat setting doesn’t create more cooling—it simply keeps the equipment running longer.

One question I hear all the time is:

“Why is my car’s A/C so much colder?”

Think about where the vents are. They’re blowing directly on your face and body, creating a wind-chill effect. Step away from those vents, and the air doesn’t feel nearly as cold. Your home’s HVAC system is designed to cool the entire house evenly—not just one person sitting a foot away from a vent.

Can you help your A/C on really hot days?

There are a few things that can make a difference.

• Keep your blinds and curtains closed during the hottest part of the day to reduce the sun’s heat entering your home.

• Don’t let your house heat up while you’re away. It’s usually easier for your air conditioner to maintain the temperature than to cool the house down 10 degrees after work.

• Make sure your filter is clean and that furniture isn’t blocking supply or return vents.

Some homeowners have experimented with lightly spraying water over the outdoor condenser during the hottest part of the day. The idea is that cooler water helps the condenser reject heat more efficiently, allowing the refrigerant to condense more effectively before returning indoors. Some people even use timers or water curtains on side-discharge units during extreme heat.

If you try this, use caution. Keep water away from electrical components and disconnects, avoid soaking the unit, and remember that hard water can leave mineral deposits on the coil over time. It’s not a manufacturer-recommended solution, but it does illustrate an important principle: the easier your outdoor unit can get rid of heat, the better your air conditioner can perform.

At the end of the day, your air conditioner isn’t trying to create “cold.” It’s simply moving heat from one place to another.

Understanding that simple concept helps explain why thermostat settings, airflow, humidity, insulation, shade, and outdoor temperatures all affect how comfortable your home feels.

The better your home keeps heat out, the less work your air conditioner has to do.

— HEATGUY

Helping homeowners understand how HVAC really works.