Show power usage in energy panel

Is your feature request related to a problem? Please describe.

Describe the solution you’d like
Add possibility of power measured in Watts in energy panel. This entity should be possible to show as a sum of other entities as three phases entities or if someone desires separate devices power.

Describe alternatives you’ve considered, if any
Provide a template which could generate sum of other entities to use as a card anywhere in HA.

Additional context
Self explanatory

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