The Vedas describe energy by the name of agni. The same agni when located in various spaces is named variously as Indra, Vāyu, Jātavedas, Vaiśvānara, Puriṣya, Śuchi, Pavamāna, Pāvaka, Aśva, Gau, Ajā, Avi etc. Some 200 Sūktas have been devoted to Agni (energy) in the Ṛgveda. Agni is noted to devour his parents (matter) soon after its birth. This points nothing else but conversion of matter into energy. The present paper tries to discover the concept and various forms of energy known to the Vedic people. It also discloses the real meanings of Pūruṣamedha, Aśvamedha, Gomedha, Ajāmedha and Avimedha as intended by the Vedic seers in the context of energy. The solar and geothermal energy was allowed to be harnessed for various useful applications. The very idea that life on earth is sustained by sun alone is not acceptable to the Vedic seers. According to them, the earth is equally responsible for sustenance of life on it. The planets without their own energy are unable to sustain life even in the presence of the sun. It is permutation and combination of solar radiation and geothermal energy that generates the atmosphere conducive to sustain bio-life on the earth.