Smart meters can show you how much energy your devices are actually using, even when on standby. Tools like nmap and Wireshark can help you map-out your home network and monitor how chatty your devices are, even when you think they are turned off.
Nothing is truly turned off unless it is unplugged. I have an integrated microwave that looks asleep but it is constantly waiting for you to touch its fascia so that it can wake up or open its door for you. My set-top boxes have powered down their storage media but they are still polling servers on the internet for updates and waiting for an IR signal from the remote. The smart TVs are also waiting for IR signals or your voice. Some even record your voice and analyse it in a buffer just on the off-chance that you are talking to it. Always listening.
Your home might be full of devices just waiting for you to address them, with a button press or voice command. Constantly waiting and consuming power. All in the name of efficiency.