For energy metering I have to define seperated energy meters for import and export of energy.
I like to be able to configure in energy configuration an energy meter that support one measurment that can ascend and descent to allow net metering.
Background:
In Germany we measure net power. Net power is the sum of power on line 1, 2 and 3.
Example:
L1: 50W
L2: 100W
L2: -200W
net= -50W
The famous and cheap energy meter Eastron SDM630 provides net energy consumption as one measurement. E.g. above example with -50W (export) will decrease kWh value.
On picture you see me cooking lunch at 13:06 
Modbus definition for SDM630’S “net kWh” is:
- address: 396
count: 2
data_type: float32
input_type: input
name: Net kWh
precision: 3
slave: 1
unit_of_measurement: kWh