You are leaving for a week and nobody will be home. Why pay to cool an empty house?
It is a fair question, and the instinct to shut everything off makes sense. But in South Jersey, where summer humidity runs high for months at a time, turning your air conditioner completely off can cost you far more than the electricity you save.
Here is what actually happens to a closed up house without cooling, and the setting most homeowners should use instead.
The Short Answer
Do not turn the system off. Set the thermostat higher instead, usually somewhere between 80 and 85 degrees.
That range captures nearly all of the energy savings while keeping your air conditioner cycling often enough to control moisture. A completely unconditioned house in July does not just get hot. It gets humid, and humidity is where the real damage happens.
Why Humidity Is the Real Problem
Your air conditioner does two jobs. It lowers temperature, and it removes moisture from the air as that air passes over the cold evaporator coil.
When the system is off, the second job stops entirely.
- Indoor humidity climbs steadily in a closed house
- Moisture soaks into drywall, wood, upholstery, and carpet
- Mold can begin growing within 24 to 48 hours in the right conditions
- Musty odors set in and are difficult to remove afterward
- Wood flooring, cabinetry, and doors can swell and warp
Our coastal location makes this worse than it would be inland. Summer dew points here regularly sit high enough that an unconditioned house reaches uncomfortable humidity levels within a day.
What Else Heat Does to an Empty House
Beyond moisture, sustained indoor heat causes its own set of problems.
- Attic and upper floor temperatures can climb well above outdoor readings
- Electronics, batteries, and appliances sit in conditions outside their rated range
- Wine, medications, candles, and some cleaning products degrade
- Houseplants rarely survive a week without conditioning
- Pets left with a sitter face genuinely unsafe indoor temperatures
The Savings Are Smaller Than You Think
The logic behind shutting the system off assumes you save the full cost of running it. In practice, much of that is recovered on the back end.
- A house that has absorbed a week of heat takes hours to bring back down
- Walls, floors, and furniture hold heat and release it slowly
- The system runs at full capacity for an extended period on your return
- Dehumidifying a saturated house takes considerably longer than cooling it
Setting the thermostat to 82 instead of turning it off captures most of the savings without any of the recovery cost or moisture risk.
What Setting to Use
The right number depends on how long you are gone and what is in the house.
- Weekend trip: 78 to 80 degrees
- One week: 80 to 82 degrees
- Two weeks or longer: 80 degrees, and consider having someone check on the house
- Homes with pets: 78 degrees maximum, regardless of trip length
- Homes with wine, artwork, or musical instruments: 75 to 78 degrees
Avoid going above 85. Past that point, humidity control becomes unreliable because the system simply is not running often enough.
If Your System Has a Dehumidify Mode
Some newer thermostats and variable speed systems can prioritize moisture removal over temperature.
- Set a humidity target between 50 and 55 percent
- The system runs specifically to control moisture rather than temperature
- This is the ideal setup for extended absences
- Not all equipment supports it, so check your thermostat before you leave
Other Things Worth Doing Before You Go
A few small steps reduce the load on your system and lower the risk of coming home to a problem.
- Change the air filter, since a clogged filter over a long absence increases freeze risk
- Close blinds and curtains to cut solar heat gain
- Confirm all supply and return vents are open
- Empty the refrigerator of anything that will spoil
- Shut off the water supply to the washing machine and dishwasher
- Consider shutting off the main water supply for trips longer than a week
- Turn the water heater to vacation mode if it has one
That water shutoff point matters more than people expect. A supply line failure in an empty house is one of the most expensive things that can happen to a home, and nobody is there to notice it.
Smart Thermostats Make This Easier
If you travel regularly, a smart thermostat pays for itself in convenience alone.
- Set a vacation schedule before you leave
- Adjust the temperature remotely if plans change
- Begin cooling the house a few hours before you arrive home
- Receive alerts if indoor temperature or humidity moves outside your set range
- Some models notify you if the system stops running entirely
That last feature is genuinely valuable. Knowing your AC failed on day two of a ten day trip gives you time to arrange help before the house sits in the heat.
The Risk of Coming Home to a Failed System
An air conditioner that quits while you are away leaves the house unconditioned for as long as you are gone, which is exactly the scenario the higher thermostat setting was meant to prevent.
- Systems that are already struggling often fail under sustained runtime
- Weak capacitors, low refrigerant, and marginal airflow are common triggers
- A pre-trip tune-up catches most of these before they matter
- Leaving a known problem unaddressed before a long absence is a gamble
If your system has been making new noises, cooling unevenly, or running longer than it used to, get it looked at before you leave rather than after.
When Should You Call an HVAC Professional?
Call before an extended trip if your system has shown any warning signs, if you are unsure whether your thermostat supports a vacation or humidity setting, or if your home has struggled with humidity in past summers. A pre-vacation inspection verifies refrigerant charge, tests electrical components, checks airflow, and confirms the condensate drain is clear, which addresses the failures most likely to occur during sustained runtime.
It is also worth asking about whole-home dehumidification if your house tends to feel damp even when the AC is keeping up on temperature.
Trust BMB & Sons for Summer Comfort and Peace of Mind
At BMB & Sons, we help South Jersey homeowners keep their systems running reliably through the hardest part of the season, including the weeks nobody is home. Our technicians catch the small problems that turn into failures under heavy summer load, and we can walk you through the right settings for your equipment before you travel.
As a family owned and operated company serving the area since 2014, we offer honest recommendations, same-day service, and long term comfort solutions you can trust.
Heading out of town this summer? Contact BMB & Sons today to schedule a pre-vacation system check and leave knowing your home is protected.
