See updated version at https://brettbeeson.com.au/energy-monitoring-circuit-positives-and-negatives/
Some, it all seems pretty simple, right? It’s just import, export, consumption. This post clarifies the sign (+ or -) conventions I use which seem to make things easiest.
| Name | Sign | Meaning |
|---|---|---|
| Import | +ve | Energy from grid |
| Export | +ve | Energy to grid. |
| Consumption | +ve | Consumed in the building |
| Net | +ve Import and -ve Export | Power reading at meter |
| Production | +ve | Production. Can be solar, battery, wind. Note battery is just time-shifted solar or wind. |
CV1 
CV2 
C3
Each of the three images has a ‘control volume’ where we measure power flow across.
CV1 is the meter: the ‘Net’ reading is positive (import) or negative (export) at any time.
CV2 simply breaks Net into positive (importing) and negative (exporting).
Import - Export = NetC3 shows production and consumption. Note production is of any kind (e.g. solar, battery, whatever). Battery storage within the building is consider production, it’s just shifted in time.
Production - Consumption = NetSo putting this together:
Production - Export + Import - Consumption = 0