As others have already stated, depending on user settings, they will automatically come back on after a power outage.
Other things to keep in mind.
There is three states of sleep a computer can be in.
Standby, Screen off, CPU, hard drives and fans at full power.
Sleep, where memory is at full power to keep the operating data fresh, but the CPU, hard drives, fans, and screen are powered down.
Hibernate, where the entire RAM data load is saved to a file on the hard disk and everything shuts down.
If it was in one of the two former states, then it would have to reboot from scratch if it lost power.
If it was in the last state, then it won’t.
Depending on settings, normally it will go into standby with 15 to 30 minutes of disuse. Then sleep with another half or one hour of disuse. If it
sets long enough, and you have it set up to do so, it will go into hibernation after several hours of disuse.
Normally a TV will automatically do an autoscan a few minutes after power is restored. If you try to turn on the TV right after the power comes on, it
hasn’t had a chance to scan for active channels and fill the channel list. So you will have to initiate the process yourself. But if you wait 10 to
20 minutes before turning it on, you should see that it has regained situational awareness and has a rudimentary list of working channels already on
edit on 24-2-2011 by Mr Tranny because: (no reason given)