ADE9000 Calculating total energy over amount of time

Dear guys, 

for my hobby project I'm using ade9000 to monitor voltages current energy .

I've been able to calculate without  problem Instants Voltages , Current and   Power.    

It's really not clear btw ,  how  I have to calculate  total energy over a period of time? 

To be clear I would like , as example,  to calculate total drained energy from my system Ex. 9am to 3pm.  

Regarding time is easy, just need to activate the monitoring,  but what about getting energy data ? 

Generally I don't understand if and how ade 9000 works under this point of view, can someone explain or drive me in the right direction?