An EPS tap was a device connected to the EPS network aboard a starship or space station. It enabled personnel to drain energy from the EPS to power other devices or systems.
Geordi La Forge told Leah Brahms to watch out for a power tap while crawling through a power transfer conduit in 2367. (TNG: "Galaxy's Child")
When trying to repair the atmosphere of Penthara IV, a burst from the deflector dish was fired at the planet, followed by a discharge of all EPS taps through the phasers. (TNG: "A Matter of Time")
An overly-enthusiastic Montgomery Scott almost accidentally touched an EPS tap after boarding the USS Enterprise-D in 2369. A serious injury would surely have resulted had Geordi La Forge not intervened. (TNG: "Relics")
In 2373, Chief Miles O'Brien ordered his engineers to set the USS Defiant's EPS taps to level three. (DS9: "For the Uniform")