The idea of "Tachyon energy" was proposed in a pseudoscientific book titled Tachyon Energy: A New Paradigm in Holistic Healing (1999) written by Gabriel Cousens and David Wagner, two proponents of spiritual medicine who pretended that they were doing science. In the book they claimed that "tachyon energy" can explain everything from acupuncture, chi, homeopathy, and reflexology to Yoga and Chakras.
Since the book was written many New agers have embraced the concept claiming that it has bridged the gap between science and spirituality. Some have even set up websites to feed off the gullible to sell their "Tachyon energy" products.
There is no scientific evidence that "Tachyon energy" exists and the energy has never been tested in any experiment. It is just another name for the belief in vitalism. It is no different than any other supposed metaphysical force such as Chi, prana or vril.
 No relation to science
Tachyon Energy has no real relation to the hypothetical particle called a "tachyon" put forward by the physicist Gerald Feinberg. Yet New Agers in hope to sound more "scientific" in some of their books claim that there is a relation.