. Simply plug it into a powered mains socket & then plug your appliance into it. The meter will monitor the e nergy usage of your appliance. The Energy Saving Power Meter will measure the energy use (and calculate costs) of running household appliances. This helps you lower your power bill & reduce carbon emissions as you discover which appliances are the worst energy offenders & then work out ways to limit their use. You can plug any 13 amp-rated household appliance into this power meter in plug adapter format to access its energy consumption & carbon footprint..