One day you’re running the AC at 2 pm, and the furnace at 7 am, and you start wondering if your HVAC system is broken or going to break. It’s not uncommon to run AC and Heat in the same week. Idaho Falls fall weather does this every year.
Running your AC and heat in the same week is completely normal here. It doesn’t mean your system is failing, and it doesn’t automatically waste energy either. It’s just how HVAC systems handle a shoulder season with big temperature swings.
Let’s break down why this happens and how to manage it without running up your energy bill.
Why Idaho Falls Sees Such Big Temperature Swings
Fall in eastern Idaho is unpredictable. Mornings can start in the 30s and 40s. Afternoons can climb into the 70s. That’s a 30 to 40 degree swing in a single day.
This happens because clear skies and low humidity let the ground lose heat fast overnight. Then the sun heats things up quickly once it’s out. Add in cold fronts dropping down from Canada, and you get whiplash weather through October and into November.
Your home reacts to those swings just like you do. It gets cold at night and warm during the day. Your HVAC system is simply keeping up.
Is It Bad for Your System to Switch Between AC and Heat?
No, not if your system is healthy. Modern HVAC systems are built to switch modes as needed. Short bursts of cooling in the afternoon followed by heating overnight won’t damage a well-maintained unit.
What can cause problems is constant short-cycling, meaning your system turns on and off rapidly and repeatedly. That puts extra wear on components over time. If you notice your AC or furnace kicking on for just a minute or two at a time, that’s worth a service call.
A single tune-up before the swingy season hits can catch small issues before they turn into bigger ones.
How to Manage Your Thermostat During Fall Swings
You don’t need to babysit your thermostat all day. A few small habits go a long way.
Set a consistent daytime and nighttime temperature instead of chasing every swing. The U.S. Department of Energy recommends programming your thermostat to set back 10 to 15 degrees during the hours you’re normally out of the house or asleep, and that same steady approach works well through fall.
Avoid making big manual adjustments every time the temperature outside shifts. Constant overrides make your system work harder than it needs to.
If you have a programmable or smart thermostat, let it do the work. Set a schedule once and stop micromanaging it daily.
Additionally, make sure to change your air filter before the season gets busy. A clogged filter forces your system to strain no matter which mode it’s running in.
Signs Your System Needs Attention, Not Just a Season Change
Some symptoms go beyond normal fall behavior. Watch for these:
Your system runs constantly without reaching the set temperature. That points to airflow or capacity issues, not just outdoor swings.
You hear grinding, rattling, or clicking sounds during startup. Odd noises usually mean a mechanical problem.
Your energy bill jumps sharply compared to last fall. A sudden spike often signals reduced efficiency somewhere in the system.
One room stays too hot or too cold no matter what you do. That’s usually a ductwork or balance issue, not weather.
If any of these sound familiar, it’s time for a professional look instead of guessing.
Get Ahead of Winter With a Fall Tune-Up
Idaho Falls weather isn’t going to stop swinging between now and December. A quick maintenance visit now means your system is ready for whatever comes next, whether that’s one more warm afternoon or the first hard freeze.
Contact RSJ Mechanical today to schedule your fall HVAC tune-up and head into winter with confidence.
Frequently Asked Questions About Running Both AC and Heat
Should I switch my thermostat between heat and cool modes myself, or leave it on “auto”?
Most modern thermostats handle this better than manual switching. Auto mode lets the system choose heating or cooling based on your set temperature, without you remembering to flip a switch every time the weather shifts.
Does running AC and heat in the same week affect the humidity in my home?
It can. Cooling pulls moisture out of the air, while heating tends to dry it out further. If your home feels unusually dry or stuffy during fall swings, a whole-home humidifier can help balance things out.
How often should I get my HVAC system serviced during the fall transition?
Most homeowners in Idaho Falls benefit from one professional tune-up each fall before the winter heating season begins. This catches minor issues early and keeps both your heating and cooling components running efficiently.