Is it true that on standby they use 50% of the power when in use.

Is it true that on standby they use 50% of the power when in use.

NO. Most sets when put into standby just keep a small voltage supply present to the control micro, so the remote will turn the set back on. Some older sets did leave several signal processing circuits powered up and only removed the HT supply to the line output stage.

If you're concerned that your TV (television!!) is going to reduce your Chang budget - forget it.