At the moment, our Energy Tracker https://customerservices.npower.com/app/answers/detail/a_id/285/session/L3NpZC9SSnhqUWFuaw%3D%3D/kw/tracker/r_id/166/sno/1 isn't linked to our billing system, so it won't display the meter reads we hold for your account.
Instead, it's intended as a tool to help you record your electricity use on a regular basis, so you can understand how much electricity you're using and stay in control.
As we improve our central systems, we'll look to provide more data within Energy Tracker.