Reserve power
Reserve power, also known asemergency backup power,power reserves,energy reserves, oremergency reserves, was anenergy resource used for operating astarship when the mainpower was offline.
Aboard theECSHorizon,Paul Mayweather instructed hisbrother to transfer reserve power to thehull plating to stand against a pirate attack. (ENT: "Horizon")
Twelveyears after the outcome of theHuman-Xindi conflict, CaptainTrip Tucker apologized for the low lighting aboard the ship toJonathan Archer as they're using only reserve power. (ENT: "Twilight")
In analternate timeline,Lorian ordered to re-route reserve power to the hull plating to stand an attack. (ENT: "E²")
WhenHikaru Sulu wasin command of theUSSEnterprise and all of the ship's systems went down he ordered to switch to reserve power. (TOS: "The Savage Curtain")
When theUSSSaratoga met theWhale Probe, thescience officer reported that all systems failed and the ship was functioning on reserve power only. (Star Trek IV: The Voyage Home)
TheUSSEnterprise-D could maintainlife support for severalmonths using only reserve power. (TNG: "The Last Outpost")
When theEnterprise-D took aboard ashuttlecraft with adoppelgänger ofCaptainPicard from another timeline,Data had to connect the ship to the shuttlecraft which lost all of its primary and reserve power. (TNG: "Time Squared")
Encountering thePakled shipMondor, Data noticed thatsensors indicateengineering problems and they're experiencing total guidance system failure, with less than twenty fourhours of reserve power. (TNG: "Samaritan Snare")
In2370, a disabledHideki-classshuttle wastractored intoDeep Space 9 after having its engines completely disabled and its life support systems were operating on reserve power. (DS9: "Profit and Loss")
WhenB'Elanna Torres placed the projectors aboard theUSSVoyager she questioned that the ship had enough reserve power to operate them.The Doctor told her to shut down life support on severaldecks. (VOY: "Projections")