Unplugging iPhone charger when not charging

Hi, randomly specific (and possibly dumb) question here:

Since I've heard that iPhone chargers draw power whenever they're plugged in (regardless of whether the phone's attached), I try to unplug my charger whenever I'm not charging my phone. After an apartment reorganization, it's most convenient for me to plug my charger into an extension cord instead of directly into a wall outlet. If I just unplug the charger from the extension cord, am I stopping the unnecessary power draw, or does the extension cord itself (an ordinary cheap one) still draw power because it's plugged in? I.e. should I be unplugging the charger from the extension cord, or the extension cord from the wall? (Or does neither way have any real effect?)

Thanks,
Adam