The Empath - S3-E12
Plot hole: Spock calculates that it will take 72 hours for the solar flare to pass, and Kirk orders the Enterprise out of the area. 3 days is a long time to go without food or water, and as the station is deserted as far as they know, there'd be no way to supply themselves, but the Enterprise leaves without a second thought.
Chosen answer: If they're in orbit, they're being pulled along by the planet's gravity well, therefore, impulse engines would only be used for minor corrections and would be "on standby" while in orbit, but not active. (Like keeping your car idling without revving the engine and creating plumes of exhaust).
Captain Defenestrator
Thank you for the info.
Movie Nut