There are some pretty cheap plugs with metering function on the market now:
BELIFE® Smart Plug - 4 stuk - Slimme Stekker met ENERGIEMETER - Google Home & Amazon Alexa Compatible - Smart Home
(Apologies for the Dutch).
they are offered for €50 for a set of 4 (€12,50 a piece).
Currently there is no app to use them on the Homey.
Is someone working on an App for these plugs?