Virtual sensor to find out electric consumption of a given appliance

Hello everybody
I have installed a general utility meter which gives me the whole house consumption.
Now I’d like to have a sensor showing me the consumption of a given appliance. I guess it can be done by knowing the increasing of consumption ( active power and reactive power) when such appliance is on. I cannot figure out how to get the previous values and actual values to make the difference an so trigger an automation which should accumulate the active power when such appliance is on.
Could you please lend me a hand with this issue?
Thank you in advance

Have a look here
Powercalc - Virtual power sensors - Share your Projects! / Custom Integrations - Home Assistant Community (home-assistant.io)

Thank you vingerha, but this is not what I’m looking for. I don’t need an estimation as I already have two sensors measuring active and reactive power.