Since some people might not know the history here, back in the vacuum tube days, you needed to let something like a TV warm up for a few minutes before it would

Since some people might not know the history here, back in the vacuum tube days, you needed to let something like a TV warm up for a few minutes before it would work. Vacuum tubes contain a filament (much like the one in a light bulb) and it needed to heat up the cathode before the tube would start working. Later, manufacturers introduced "instant on" TVs that would keep the filaments powered even when the set was "off". This wasted electricity but you didn't need to wait for the tubes to warm up.