Reserve power
Reserve power, also known as emergency backup power‎, power reserves, energy reserves, or emergency reserves, was an energy resource used for operating a starship when the main  was offline.

Aboard the , Paul Mayweather instructed his brother to transfer reserve power to the hull plating to stand against a pirate attack. ()

Twelve years after the outcome of the Human-Xindi conflict, Captain  apologized for the low lighting aboard the ship to Jonathan Archer as they're using only reserve power. ()

In an alternate timeline, Lorian ordered to re-route reserve power to the hull plating to stand an attack. ()

When Hikaru Sulu was in command of the  and all of the ship's systems went down he ordered to switch to reserve power. ()

When the  met the Whale Probe, the science officer reported that all systems failed and the ship was functioning on reserve power only. ()

The  could maintain life support for several months using only reserve power. ()

When the Enterprise-D took aboard a shuttlecraft with a doppelgänger of Captain Picard from another timeline, Data had to connect the ship to the shuttlecraft which lost all of its primary and reserve power. ()

Encountering the Pakled ship Mondor, Data noticed that sensors indicate engineering problems and they're experiencing total guidance system failure, with less than twenty four hours of reserve power. ()

In 2370, a disabled  shuttle was tractored into Deep Space 9 after having its engines completely disabled and its life support systems were operating on reserve power. ()

When B'Elanna Torres placed the projectors aboard the  she questioned that the ship had enough reserve power to operate them. The Doctor told her to shut down life support on several decks. ()

See also 
 Auxiliary power
 Emergency power
Energy