In general, 80 degrees is too hot for a house if people are inside. However, if people aren't home during the day or for vacation during the summer, an indoor temperature of 80 degrees can save energy until you return and lower the temperature.
An influential limit
After an influential study in 2010, climate researchers often use a wet bulb temperature of 35 degrees C — roughly equivalent to 95 degrees F at 100% humidity — as an upper limit for human survival and adaptability without cooling.
For short periods of time away, like going to work, we'd recommend a temperature of around 55 – 60 degrees (F). While away on long periods of time, such as vacation, we don't recommend setting the temperature any lower than 50 degrees (F).
When temperatures exceed 100 degrees Fahrenheit outside, setting your air conditioning (AC) to around 75-78 degrees Fahrenheit is generally considered efficient. Here are some reasons for this recommendation:
Sleep experts believe the best temperature for great sleep is between 68-72 degrees Fahrenheit. But in addition to making you uncomfortable and interfering with healthy sleep patterns, being too hot at any time of day or night can cause health risks like dehydration and heat stroke.
The Safest Temperature for Humans and Pets
Heat can be dangerous, so you don't want to let your home get too hot. The absolute highest you should set your thermostat is around 82 degrees Fahrenheit.
In general, 80 degrees is too hot for a house if people are inside. However, if people aren't home during the day or for vacation during the summer, an indoor temperature of 80 degrees can save energy until you return and lower the temperature.
For the most efficient performance, set the thermostat 20 degrees lower than the temperature outside. On a 100℉ day, set it to 78℉ to 80℉ to manage utility costs. If there's a lack of airflow, the filter may need to be changed or AC vents cleaned. But it may also mean your air conditioner needs professional repair.
Just because the outdoor temperature is above 100, the Ideal temperature to set your AC unit to doesn't change — it's 78 degrees. Higher temperatures in the home are to be expected when the weather is hotter than usual, but your thermostat can still be set the same as if it were a lower temperature outside.
More importantly, it's a good idea that you keep your room at a good temperature to avoid any health problems especially for the elderly. As mentioned on the above table, your living room should ideally be between 21°C – 23°C and your bedroom should be between 17°C – 19°C.
Older bodies also hold more heat than younger ones when the temperature climbs. Glands don't release as much sweat. The heart doesn't circulate blood as well, so less heat is released from vessels in the skin.
People who live with long-term health conditions are more vulnerable to the effects of heat, including cardiovascular conditions and diabetes – with the temperature in their homes making it much harder to manage their health.
A core body temperature of 104 degrees Fahrenheit (40 degrees Celsius) or higher is the main sign of heatstroke. Change in mental state or behavior. Confusion, agitation, slurred speech, irritability, delirium, seizures and coma can all result from heatstroke. Change in sweating pattern.
The World Health Organization recommends a thermostat setting no lower than 68 degrees while you're home. If you have children or seniors in your house, that number increases to at least 70 degrees. If your house is too cold, it can cause problems with blood pressure and circulation, as well as affect your heart rate.
Minimal-risk high temperatures range from about 21 to 30 °C (70 to 86 °F) depending on the region, with maximum acceptable temperatures between 25 and 32 °C (77 and 90 °F).
What should my AC be set at if it's 90 degrees outside? If the outdoor temperature is 90 degrees, it's recommended to set your thermostat between 75-78 degrees.
The answer is to set it as high as you can to still maintain a level of comfort. The Department of Energy (DOE) recommends a setting of 78 degrees when you're home and 80 degrees when you're away. When the outside temperature is in the high 90s or more than 100 degrees, your cooling system has to work hard.
Best AC Temperature Settings While You Are Home
As you consider the most comfortable room temperature for your lifestyle and family, keep in mind that for each degree that you set your thermostat above 72 degrees, you can save up to 3% on your energy bill.
“The consensus among most scientists is that anything higher than 75 or 80 is bad for sleep and potentially detrimental to health,” Baniassadi said. Heat affects sleep because the body signals the brain that it's time to fall asleep by lowering its core temperature. Sleeping in a hot room makes this difficult.
Your AC might not cool properly due to thermostat issues, an undersized unit, or extremely high outdoor temps—so check those first. Keep an eye on airflow—replace clogged filters every 3 months, and make sure vents and ducts aren't blocked for efficient cooling.
All other dogs must have some method of conserving body heat (such as dry bedding, solid resting surfaces, heat lamps, or other provisions) if the temperature is less than 50 °F. Dogs cannot be housed in temperatures above 85 °F for more than 4 consecutive hours.
It's advisable to keep your home below 80 degrees throughout the summer. A house that's too warm can be dangerous to people, pets, and the soft surfaces in your home. Set the winter temperature to 68 degrees when you're awake and 62 degrees when you're sleeping.
But did you know that you can suffer heat stroke indoors as well as outdoors? Prolonged exposure to temperatures over 90 degrees Fahrenheit, no matter the location, can cause the body's natural cooling system to fail.