Best Thermostat Setting When It’s 100 Degrees Outside

HVAC Logo IconBy Tom MoorJuly 10, 2024
Get a fair quote
The right solution at the right price. Save 20% on average in just 4 steps.

Score an HVAC quote
Our independent team of HVAC industry insiders can score your quote to see if it’s fair.

Sharing your quote takes less than a minute

Woman adjusting the thermostat in her home

As temperatures soar this summer, it’s important to find the right thermostat setting for both comfort and energy savings. Getting this balance right not only keeps you cool but also helps protect your AC from overworking and breaking down on those really hot days. HVAC.com offers tips on setting your thermostat when it’s 100 degrees or hotter outside.

The Best AC Temperature When It’s 100 Degrees

When temperatures rise to 100 degrees, a common recommendation is to set the thermostat to around 78 degrees for a balance between comfort and energy savings. However, this recommendation can vary based on the following factors:

  1. Comfort: Some people may prefer a slightly cooler thermostat setting in the summer, such as 75-77 degrees, especially during extremely hot weather. If this temperature still seems hot, consider turning on ceiling fans in occupied rooms. The “wind chill” effect provided by ceiling fans can make it feel about 4 degrees cooler without adjusting the thermostat.
  2. Energy Efficiency: Setting the thermostat to 78-80 degrees can help save energy and reduce utility bills. Raising the thermostat during extremely hot days can save you up to 10-15% on your cooling costs, depending on factors like your home’s insulation and your AC's efficiency level.
  3. Humidity Control: In humid climates, you may want to set the temperature a bit lower to help control indoor humidity levels. If your system is struggling to remove moisture, especially on hot, muggy days, consider installing portable or whole-house dehumidifiers.
  4. System Wear and Tear Considerations. Consider setting your thermostat higher on 100-degree days to protect your air conditioner's health. Running it at lower temperatures can strain components, leading to repairs and a shorter equipment lifespan.

Consider the 20-Degree Rule

If you’re still unsure what to set your thermostat to when the temperature climbs to 100 or higher, consider the 20-degree rule. During heat waves, experts, including utility companies, recommend keeping your thermostat no more than 20 degrees cooler than the outdoor temperature. For instance, if it's 100 degrees outside, aim to set your thermostat to at least 80 degrees.

Adhering to the 20-degree rule maintains energy efficiency, prevents strain on your cooling system, extends its lifespan, and promotes lower energy bills and consistent indoor comfort.

Regular Maintenance Can Prevent Breakdowns

With 100-degree days becoming more common, regular AC maintenance is crucial. AC maintenance includes tasks like replacing air filters, inspecting and lubricating moving parts, checking refrigerant levels, and ensuring all components are working properly.

Regular maintenance also helps improve your air conditioner's efficiency and lifespan, ensuring it works reliably even during extreme heat. This reduces the chances of breakdowns and can lower your energy bills over time.

Get a fair quote
The right solution at the right price. Save 20% on average in just 4 steps.

Score an HVAC quote
Our independent team of HVAC industry insiders can score your quote to see if it’s fair.

Sharing your quote takes less than a minute

HVAC.com is your trusted advisor for all things HVAC

Chat with an advisor

Available 8 AM - 5 PM Eastern Time