One of the most significant sustainability challenges of our time is how we produce, use, and relate to energy. Today billions of people use fossil fuels like coal, oil and gas for energy. While use of these resources has greatly increased standards of living, it also has driven significant worldwide environmental impacts. The Jewish tradition teaches us to use energy wisely. In some cases, wasting energy is a violation of Bal Tashchit, the prohibition not to waste excessively. For example, the Talmudic Sage Mar Zutra stated, “One who covers an oil lamp [causing the flame to burn inefficiently] or uncovers a kerosene lamp [allowing the fuel to evaporate faster] violates the prohibition of BalTashchit” (Babylonian Talmud, Tractate Shabbat 67b). Based on this teaching of the Talmud, the Ben Ish Chai (Rabbi YosefChaim ben Eliyahu, a major Iraqi nineteenth century authority on Jewish law, in Torah Lishma section 76), addressed a case in which a person lit two wicks in oil for use at night. The person left both wicks lit throughout the night in the event they woke up in the middle of the night and needed to see. In order to prevent waste, the Ben Ish Chai instructed the man to extinguish one wick before going to bed, since were he to get up at night, he would only need the light of one wick; keeping the second wick lit would be a transgression of Bal Tashchit, the prohibition not to destroy or waste. This response shows a high degree of concern for wasting energy in a case where someone does not derive benefit from an additional use of energy. Similarly, the Ben Ish Chai discusses a case in which a person puts a large amount of oil before Shabbat in a lamp in their home in order for it to remain lit for all of Shabbat. He rejects this practice as a waste of oil and a transgression of Bal Tashchit, since the light from this lamp will not be of benefit to a person during the day in their sun-lit home. The mitzva of Bal Tashchit—do not destroy or waste—communicates a deeper Jewish message about the value of things: there is never enough to waste even if there is plenty right now. In this vein, Rabbi Samphson Raphael Hirsch teaches that God conveys through this commandment that “Only if you use the things around you for wise human purposes, sanctified by the word of My teaching, only then are you a mensch and have the right over them which I have given you as a human” (Horeb, sections 397, 398).In our time, the above views may be relevant concerning leaving lights, heaters, air conditioners, or other appliances running for all of Shabbat or during the week when a person will not derive benefit from them. Another area where this may apply is in 'standby' appliance use in most homes. According to the Energy Analysis Department of the Lawrence Berkeley National Laboratory, “a surprisingly large number of electrical products—from TVs to microwave ovens to air conditioners—cannot be switched off completely without being unplugged... A typical American home has forty products constantly drawing power. Together these amount to almost 10% of residential electricity use” (http://standby.lbl.gov/ )Energy use causes a host of serious problems such as air pollution, climate change, and mercury in fish. Studies show a correlation between air pollution and premature deaths due to lung cancer. Researchers conclude that when air pollution in a city declines, the city benefits with a directly proportional drop in death rates. Rabbi Ezra Batzri, former head of the Sephardi Rabbinical Court in Jerusalem, writes that a character trait of a righteous person (Midat Hasidut) is being careful about not damaging others even indirectly. The Mishnah expresses this concern for protecting our neighbors by instructing that tanneries, which produce noxious odors, must be sufficiently distanced from human settlements so as not to negatively affect the air people breathe in the vicinity (BavaBatra 25a). Today, we can use less energy and reduce the amount of coal and gasoline burned, diminish the health impacts from the resultant air pollution, and uphold the rabbinic advice not to damage others indirectly. We might do so by driving less, eating less meat or globalized food, or taking fewer plane trips. It is in the realm of personal consumption that Jewish thought may best inform our energy and climate challenges today and empower us to change. To generate broader changes in people our people and our world, we must start with our own actions.The prophet Isaiah repeatedly calls on the Jewish people to be a “light unto the nations.” Rabbi David Kimchi (France, 1160-1235) explains that 'light' here refers to the Torah. In our times, let us find inspiration and light in the profound teachings of our tradition that address our central challenges. And let the light that emerges from our example reveal to the world a new sustainable path. These materials are posted as part of Jewcology’s “Year of Jewish Learning on the Environment,” in partnership with CanfeiNesharim. Learn more at http://www.jewcology.com/content/view/Year-of-Jewish-Learning-on-the-Environment.Rabbi Yonatan Neril founded and directs Jewish Eco Seminars, which engages and educates the Jewish community with Jewish environmental wisdom. He has worked with CanfeiNesharim since 2006 in developing educational resources relating to Judaism and the environment.