A buffer field generator, or energy buffer, was a device capable of reducing power drain on a vessel.
In 2368, a buffer field generator was installed aboard the shuttlecraft Magellan, in order to facilitate a rescue mission into null space, in which two J'naii scientists had been stranded. As null space would have the effect of draining the shuttle's power, the buffer was necessary to beaming the scientists aboard. Upon installing the buffer, Lieutenant Commander La Forge estimated that it would reduce the power drain to the shuttle by approximately forty percent. (TNG: "The Outcast")