As temperatures continue to rise and scorching summer heat settles in, many of us find ourselves preparing for Shabbat with a new set of practical questions. How should we use the air conditioner on Shabbat? May one adjust the air conditioning vents on Shabbat? What if the house becomes unbearably hot, especially for young children, the elderly, or someone who is ill, may we ask a goi to turn the air conditioner?

In this article, we will explore the common halachic questions that arise regarding air conditioning on Shabbat, examining the relevant principles and the rulings of the Poskim, so that we can honor the of Shabbat while maintaining a comfortable and healthy home.

Asking a goi to turn on an air conditioner

Some Poskim of the previous generation wrote that it is generally forbidden to ask a non-Jew to turn on an air conditioner on Shabbat unless the heat is exceptionally severe. Rabbi Ben Zion Abba Shaul explains that although Halacha permitted asking a non-Jew to light a fire on extremely cold days—when temperatures are freezing—hot weather is viewed differently, since excessive cold presents a more immediate danger than heat.

However, many authorities have questioned this distinction, arguing that extreme heat can be no less dangerous and may, in some circumstances, pose an even greater risk than severe cold. As support, they cite the well-known account of Rabbi Yeudah haNasi and Antoninus. Before setting out on a journey during the summer, Antoninus asked Rebbi for a blessing. Rebbi initially blessed him, “May Hashem save you from the cold.” Antoninus responded that protection from the cold is relatively simple, since one can always put on additional clothing. Rebbi then blessed him instead, “May Hashem save you from the heat.” Antoninus replied, “This is indeed a good blessing,” acknowledging that there is no comparable protection from oppressive heat. This passage suggests that extreme heat can be more difficult to cope with than severe cold and highlights the seriousness with which it should be regarded when evaluating the halachic implications of excessive heat.

Adjusting the air conditioning vents.

On Shabbat, it is generally permissible to adjust air conditioning vents as long as the adjustments are made manually and not through electronic means. This means physically manipulating the vents without utilizing any electronic controls. One may also open or close the vents based on personal preference. However, it is important to note that these actions may impact the efficiency and power consumption of the air conditioning system.

Adjustments that increase or decrease the airflow may result in greater or lesser electricity usage, which is a subject of dispute among the poskim. The reason for this dispute is that when the air conditioner adjusts itself to the temperature at the new vents’ location, it may require additional energy consumption. Although we may not perceive the increase in electricity usage directly, it does occur, and more energy is being consumed at the power plant during that time.

According to Rabbi Elyashiv, it is not permitted to move the vents due to the aforementioned reason. However, Rabbi Aurbach holds the opinion that it is permissible because the Torah does not forbid actions that are imperceptible to the human senses, such as the subtle changes in electricity usage in this case. Additionally, it can be argued that this is considered “grama” (indirect use) of electricity since the increased fuel burning occurs at the power plant, which is located far away from the individual’s house. Furthermore, it is possible that no change occurs in electricity usage when moving the vents, and in such cases, there would be no grounds for prohibition (שמירת שבת כהלכתה פרק יג הלכה מ).

The permissibility of moving vents is not restricted by muktse (prohibition on handling certain items on Shabbat) because they are designed for adjustment. Furthermore, it does not fall under the category of building(בונה וסותר) , as it is analogous to opening and closing a window(חוט שני שבת ח״א עמוד רג) .

Of course, it is important to clarify that adjusting air conditioning vents on Shabbat is only permissible when the action is purely mechanical, and there is no activation of any electrical components involved. This means that the adjustment should be limited to manual manipulation of the vents without triggering any electrical mechanisms. In such cases, where the action solely relies on mechanical operation, it is considered permissible within the framework of Shabbat observance. Adhering to these guidelines ensures that the adjustments made to the vents align with the principles of Shabbat while maintaining a comfortable environment.

Navigating Rooms Controlled by Smart Thermostats.

Smart thermostats operate by detecting the ambient temperature in your home and transmitting signals to your heating and cooling system, prompting adjustments based on your pre-set schedule. According to poskim, it is permissible to enter a room with the awareness that opening the door may introduce warmer air, potentially causing the AC unit to activate. This is because the resulting change is considered “grama” (indirect causation), as there is a delay between the time the thermostat detects the change and responds to it.

Collecting water from the Air Conditioning System.

If the air conditioning unit spills water in the house on Shabbat, it is generally not permissible to place a bucket underneath to collect the water. This is because the spilled water is considered muktse. Placing the bucket to collect the water would render the bucket un-useful, which is not allowed on Shabbat (מבטל כלי מהיכנו).

However, in the event that the water creates a wet and unpleasant environment where people are staying, it is permissible to place a bucket to collect the water (גרף של רעי). Once the bucket is filled, one may then empty the water into a sink and return the bucket under the air conditioning unit to collect any further water (שמירת שבת כהלכתה פרק יג הלכה לט).

AC that spills water onto a garden.

In cases where the air conditioning unit spills water onto a garden or area with plants and grass, resulting in their growth, it is generally permissible. This is because the air conditioning was turned on before Shabbat, and the person is not actively engaged in any actions on Shabbat that contribute to the growth of the plants. Since the growth occurs as an indirect result of the functioning air conditioning unit, it is not considered a direct violation of Shabbat laws.