What's the deal with using solar power on Shabbos?

Cooking is permitted, but what of the following cases:

1) Heating water (Dud-Shemesh style)

2) Solar-powered watches

3) Solar-powered toys

What other applications are there for solar power, permissible on Shabbos?

  • Related: judaism.stackexchange.com/q/10462
    – Fred
    Commented Mar 20, 2015 at 1:37
  • 2
    "Cooking is permitted": can you source that? As I recall, it's forbidden to put a pan out in the sun to heat up and then crack an egg into it to fry.
    – msh210
    Commented Mar 20, 2015 at 2:00
  • Uvdah dchol or ma'aris ayin? Commented Mar 20, 2015 at 3:05
  • 1
    @msh210 It is permitted though to put an egg in the sun and let it cook. Your case is only prohibited as a Gezera lest someone cook on a pan that was heated up by a fire.
    – Double AA
    Commented Mar 20, 2015 at 3:11
  • Related: judaism.stackexchange.com/questions/26084/…
    – Loewian
    Commented Mar 20, 2015 at 5:29

1 Answer 1


Only actually cooking using the direct sunlight is permitted. Toldat hachama, where the sun's energy is used indirectly, e.g. by heating the cooking surface first, is prohibited Rabbinically. This would mean that "solar power" where the solar energy is converted into electrical energy would always be forbidden (including for cooking; see http://www.ohrreuven.com/pdf/night_semicha/Night%20Semicha%20Program%20Bishul%20Shiur%208.pdf which discusses individual cases you mention; the only other issue to discuss relates to the status of electricity in general on Shabbos which should not be affected by the origin of the energy).

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