The BBC published a feature about folks in the UK making their own energy-saving gadgets, such as a thermostat that checks the weather forecast and a doo-dad that monitors the efficiency of a household combi-boiler and adjusts not the temperature but the flow rates.
Dan Medhurst, who lives near Reading and who works in IT, has attached a sensor to the front of his electricity meter. It tracks the pulsating LED on the meter, which reveals how much power is flowing. The data is sent wirelessly to Home Assistant and he can check it at any time on his smartphone or computer.
It means Mr Medhurst can spot spikes in usage and, based on the time they occurred, can work out what appliances caused them. It made him realize just how much electricity his tumble dryer consumes, for example, and he also decided to turn his fridge temperature up, while still keeping the contents cold enough (5C or below).
For the rest of us, there are electrical use monitors you can buy, such as the Emporia full-home model [Amazon] recommended on Reddit and elsewhere. I’ve read in the past that they don’t usually save people money (as with calorie counts on restaurant menus, you still gotta eat) but a cheapo one I got (this one on Amazon looks very similar) identified an old plasma TV guzzling juice like no tomorrow. By identifying that one device I think it paid for itself within weeks, though it did not of course pay for the new OLED TV that replaced it. Hmm.