Exporting of data is not part of the basic app functionality.
If you enable Energy+ in the Energy app, you can export graph data at Settings > Graphs > 'Your Graph' > Export Graph Data
Exporting period
In the app you can select any start and end date period for your data export.
Resolution
The exporting options contain meter readings per 15 minutes up to 365 days, or every 24 hours for any number of days.