For transaction_type = 'flex event': when the event started
For transaction_type = 'flex period': month start
For transaction_type = 'withdrawal': when the withdrawal happened
For transaction_type = 'flex event': when the event ended
For transaction_type = 'flex period': month end
Not present for other transaction_type values
Stored to the nearest watt-hour (3dp)
For transaction_type = 'flex event': the change in energy flow during
the event relative to the baseline in kwh. +ve indicates additional energy
imported (or less energy exported). -ve indicates additional energy
exported (or less energy imported).
Not present for other transaction_type values