@Solla-topee +1, it's the number #1 feature missing for me, however duplicate to this one:

https://community.tp-link.com/en/smart-home/forum/topic/587008

  @farbenblind  I to have purchased one of your smart energy plugs and was impressed with energy metering features, I was thinking of getting more, with the understanding that they would give you a combed cost of all the plugs together. This would be an invaluable feature if not already available. 

I would also like this feature. 
it would be great for figuring out what certain groups of devices are using. For example,  could add all the fridges to a room, and easily see what we're spending on refrigeration. Or other aspects. But without having to add individual devices up.