Why Your AC Struggles in Extreme Heat (And What You Can Do About It)
When the outside temperature climbs into the 90s or 100s, even a brand-new air conditioner can have a hard time keeping up. It’s frustrating, but often, it’s not a sign that your system is broken.
Here’s what most homeowners don’t realize: your HVAC system was never designed for these kinds of extremes. And with hotter days becoming more common, especially across the U.S., more people are running into the same issue, your home just won’t stay as cool as you want it to during peak heat.
How AC Systems Are Actually Designed
Most residential HVAC systems are built to cool your home to about 20 degrees lower than the outside temperature. So if it’s 100°F outside and you’re trying to hit 72°F inside, that’s likely not going to happen.
In fact, if you’re holding 76–78°F indoors while it’s blazing outside, your system is probably doing exactly what it was designed to do.
Tips from an HVAC Contractor: What Actually Helps
Here are simple but effective ways to help your AC system do its job when temperatures are at their worst:
1. Change Your Air Filter
A dirty filter restricts airflow and forces your system to work harder. Change it at least once a month in the summer.
2. Limit Door Openings
Every time you open a door, hot air floods in. Try to limit traffic in and out during peak heat hours.
3. Keep Blinds and Curtains Closed
Direct sunlight heats your home fast. Use blackout curtains or keep blinds closed on sun-facing windows during the day.
4. Avoid Heat-Generating Activities Midday
Don't run your dryer, oven, or stovetop during the hottest part of the day. Instead, order takeout or prep cold meals.
5. Don’t Set Your Thermostat Too High When You’re Gone
If you set your thermostat to 85°F while you're at work, it might never catch back up when you return. Set it a little higher than your usual temp, around 78°F, but not so high that your system can’t recover.
6. Let It Cool More at Night
Drop your thermostat a few degrees at night. Let the home cool deeply overnight, it will take longer to heat up during the day.
7. Gently Rinse Your Outdoor Unit
Use a hose with light pressure to rinse dirt and debris from the outdoor coil (the part that looks like a radiator). Be gentle, too much pressure can bend the fins.
If it’s very dirty or hasn’t been cleaned in years, call an HVAC technician. A chemical cleaning might be needed.
Common Questions and Smart Workarounds
“My system runs 12 hours a day, is that normal?”
Yes. Many people report 10–12 hours of runtime in the summer. If your home holds steady at 75–78°F and doesn’t feel overly humid, your system is working.
“Is it better to leave the thermostat at 72 all day or raise it while I’m gone?”
If comfort is your priority, keep it steady. Constantly raising and lowering the temp can make your system work harder, especially when it’s trying to cool down in the late afternoon heat.
“Upstairs is always hotter, how do I fix that?”
Try:
- Using blackout curtains upstairs
- Partially closing vents downstairs to force more air upward
- Running ceiling fans to help circulate air
- Checking if your attic fan is set to the right temp (around 90–100°F)
“What about duct cleaning or return vents?”
Yes, clean your return vents. If you have pets, you’d be surprised how much hair and dust gets trapped. A vacuum or shop vac can help improve airflow.
When It’s Time for an Upgrade
If your system is more than 10–15 years old, even regular maintenance won’t restore its full performance. Over time, air conditioners lose capacity, just like older car engines wear down. Some systems lose 20% or more efficiency after a decade.
New systems cost more up front but can be:
- More energy efficient (SEER 16+ vs SEER 10–12)
- Quieter and more consistent
- Better at handling high humidity
- Covered under new warranties
If you’re upgrading, get a full quote and make sure your HVAC pro does a load calculation, not just a “same size as before” swap.
Don’t Forget: Make Sure Your HVAC Pro is Insured
Before hiring anyone to work on your AC system, confirm they carry proper insurance. This protects you and them in case something goes wrong.
Here’s what to look for:
- HVAC contractor insurance California – Required for licensed work in the state, includes liability and workers comp.
- HVAC liability insurance – Covers property damage or injury caused during the job.
- HVAC business insurance – Broader protection that covers tools, equipment, and completed work.
- HVAC workers compensation insurance – Important if they have a crew on your property.
If you're an HVAC professional reading this: your insurance coverage isn’t just for peace of mind, it’s a signal to homeowners that you take your work seriously.
Take Care of Your Equipment
If your AC can’t cool the house to 72°F on a 100°F day, it’s not broken, it’s just maxed out. Focus on supporting your system instead of fighting it.
Use these tips, take care of the equipment, and work with insured professionals when needed. And if your home still isn’t comfortable, it may be time to think about insulation, attic airflow, or upgrading to a more efficient system built for today’s heat.