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[8] Timers on Shabbos: How, When, and for What Purpose?


The Mishna (Shabbos 17b) records a dispute between Beis Hillel and Beis Shammai regarding whether one can leave materials in a vat that will dye them over Shabbos, we rule leniently. In other words, may we allow our vessels to perform a forbidden work over Shabbos, provided that the process began before Shabbos entered (Shulchan Aruch OC 252:1, Rambam Hilchos Shabbos 3:2).

Nowadays in the age of technology, while we know that the active usage of electricity is forbidden (see the first paragraph here), the question arises can we use preset timers to switch on/off lights, the TV, dishwasher, kettle, coffee maker, hotplates, etc?


R’ Moshe Feinstein (Igros Moshe OC 4:60) writes that one may only use timers on Shabbos for one’s lights. In his opinion, timers are akin to instructing a non-Jew to perform a melacha on one’s behalf which is prohibited. Additionally, it isn’t respectful for Shabbos. However, as people always had non-Jews come into their houses to light and extinguish their lights, lights remain an exception.

Nonetheless, most Poskim disagree and maintain that one may set timers for other electrical appliances too. As such the usage of timers on Shabbos and Yom Tov is widespread amongst Torah Jewry including for some other appliances, as detailed below (Chazon Ish OC 38:2, Yabia Omer 3:17, Minchas Shlomo 1:11:8, Tzitz Eliezer 1:20:9, and Shemiras Shabbos Kehilchasa 13:23).

Interestingly, R. Shlomo Zalman Auerbach (Meorei Eish, ch. 4), while allowing the usage of timers, recommends declaring them ownerless (hefker) in order to avoid the issue of Shevisas Keilim (work done by one’s utensils on Shabbos) according to the opinion of the Bach (OC 246:2) who is particular.


Noisy appliances may not be in use at all over Shabbos, whether by being left on from before Shabbos or by setting a timer to turn it on. This is because of the prohibition against causing excessive noise in a way that could denigrate Shabbos (Minchas Shlomo 2:20). This is known as 'Hashmoas Kol' or 'Avsha Milsa' (Remah OC 252:5) and is also prohibited on Yom Tov (Ohr HaShabbos 4 P. 19).

Examples of prohibited usages include:

  • TV

  • Radio

  • Stereo

  • Dishwasher

  • Washing Machine

  • Bread Machine

  • Vacuum Cleaner (e.g. Robot vacuums or operated by non-Jewish helpers)

  • Coffee Maker (for quiet coffee makers see below)

In a case of financial loss, one may be lenient to set a timer before Shabbos/Yom Tov even for the above appliances (Remah 252:5; Magen Avraham 21; Pri Megadim, M.Z. 7; Aruch Hashulchan 8). The same leniency applies to alleviate physical discomfort (The Aura of Shabbos page 74:footnote 8).

It is worth noting that setting an alarm clock is allowed because alarms are commonly set well in advance there is no issue with the disgrace of Shabbos (similar to Remah 252:5, Harav Yisroel Belsky quoted in Shulchan Halevi 1 P. 98-99).


The following appliances run silently and as such may be used with a preset timer on Shabbos:

  • Lights

  • Hotplate - See usage guidelines here

  • Air Conditioners / Heaters / HVAC Systems - Even though these can be noisy they are permitted for multiple reasons. a) These are commonly controlled by thermostats, b) because of the mitzvah of Oneg Shabbos, c) the noise itself isn't from a prohibited action, therefore, Avsha Milsa doesn't apply (Rav Yisroel Belsky, Hilchos Shabbos B’Shabbos 1 P. 80).


When it comes to using a timer to enable cooking or baking it is more complicated. Examples include using a timer to schedule the following appliances to turn on during Shabbos:

  • A pre-filled electric kettle

  • An oven with food inside

  • A Coffee Maker with the coffee grounds and water inside already (if noisy this is prohibited regardless, as above)

The issues discussed in the Poskim include:

1) The prohibition to leave something cooking on Shabbos on an uncovered flame (Chazon Ish OC 37:21; Minchas Yizchok 4:26:10-1).

2) Some compare it to the prohibited case in the Mishna of adding water to a vessel before Shabbos that will later extinguish a candle (Tzitz Eliezer 2:6:3; Oros Ha’Shabbos 45).

3) There is also the concern of Ma'aros Ayin when those who the cooking/baking might not realize that it was set on a timer before Shabbos (the issue of Ma'aros Ayin on Shabbos is also discussed in Igros Moshe O.C. 1:96). See Nodeh Beyehuda (2:30) who prohibits the use of an umbrella opened before Shabbos for this reason.

4) In addition, there are some that are strict simply due to the fact that the melacha completely begins on Shabbos (as Rabbi Hershel Shechter noted here in regards to using lawn sprinklers on a timer).

For these and other reasons, many halachic authorities forbid using a timer to cook, bake or to brew coffee on Shabbos.

However, some permit it in the case of monetary loss or illness, provided that the system is completely set up before Shabbos and all food or drink is already in place before Shabbos, such that no adjustments will need to be made on Shabbos itself (Or L’Tzion 2:31:18; Yerushas Peleita 16. Melameid L’Ho’il, Even Ha’Ezer 3:58). As such, in cases of pressing need one could rely on the ruling of Rabbi Moshe Heinemann (Star-K Rabbinical Supervisor) who reportedly allows quiet coffee makers to be set on a timer.

Mechanical Timer (left) and Digital Timer (right)


Until recently, most people used mechanical timers but with the more sophisticated digital timers now widely available, I would recommend getting these for multiple practical reasons:

  1. Being able to set multiple on/off cycles (usually 8+) over seven days helps immensely when scheduling over multiple days of Yom Tov and Shabbos

  2. These are far more accurate and reliable than their mechanical counterparts

  3. They retain the time from week to week which means that if you're keeping the same schedule there is no need to adjust anything.

Digital timers can be purchased at most major stores, including on Amazon here for under $12 (no, I don't get a commission!).


Obviously, digital timers can not be adjusted without pressing electric buttons and as such may not be adjusted under any circumstances and have a status of Muktza (i.e. Muktza Machmas Gufo due to it being intrinsically unprepared for Shaboos).

When it comes to manual mechanical timers though, there is a dispute where some maintain that these are muktza and can therefore not be adjusted at all on Shabbos (Igros Moshe OC 4:91:5; YD 3:47:4, Minchas Yitzchak 2:110, and Tzitz Eliezer 1:20:9).

However, others maintain that mechanical timers are not muktza (Minchas Shlomo 1:11:8, 1:13, Yabia Omer 3:18:2, Shemiras Shabbos Kehilchasa 13:25). Even according to these opinions, one may not adjust the timer to switch the appliance on or off earlier than planned (because this action causes a forbidden melacha to occur on Shabbos). However, one may adjust the timer in a preventative way that just prolongs the existing state. This means adjusting the pins to prevent/delay a timer that is currently on from switching the appliance off or to prevent/delay a timer that is currently off from turning on. Still, these options should only be relied upon in a case where there is a pressing need (Orchos Shabbos 29).

If you have any questions, please don't hesitate to contact me


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