Welcome! What’s the brand and model of the Z wave current sensors? I’m sure there will be multiple ways to do this, but someone might’ve already created one for that specific model.
Meanwhile, you might also want to take a look at the various logging projects, as many people use those to monitor energy use.
There’s a good round up thread here:
You can also take a look at the quick browse lists in the community – created wiki for logging smartapps and project reports.