PV export

The same two devices, with the PV system now permitted to export. Reversing the grid changes its kind rather than its sign: it stops being a source and becomes a sink, which is all it takes to switch on the export channel and its compensation.

What this case shows

• An exporting grid is a sink, not a source with a negative reading.
• Export compensation is earned by the sources the export was drawn from.
• Zero gross power guards to zero rather than dividing by zero.

Each snapshot below is one set of readings on this wiring, drawn as a flow chart — how to read it.

Export surplus

PV export · snapshot 01

The PV system outruns the house; the surplus leaves through the grid.

Reading	W	Of gross	Share	Made of
Gross power	900 W	1		pv1 900 W
Grid import	0 W	0		nothing drawn from the grid
Grid export	400 W	4/9		pv1 400 W
PV production	900 W	1		pv1 900 W
Charging power	0 W	0		no battery charging
Discharging power	0 W	0		no battery discharging
Standby power	0 W	0		no standby draw
Self-consumption	500 W	5/9		pv1 500 W
Metering imbalanceok	0 W	0		readings reconcile exactly
Home base load	500 W	5/9		unmetered remainder of consumption

Ribbon widths are watts in every view. Hover, focus or tap a ribbon to see the sensor behind it.

Export all

PV export · snapshot 02

Everything the PV system makes is exported: the home base load is exactly zero.

Reading	W	Of gross	Share	Made of
Gross power	900 W	1		pv1 900 W
Grid import	0 W	0		nothing drawn from the grid
Grid export	900 W	1		pv1 900 W
PV production	900 W	1		pv1 900 W
Charging power	0 W	0		no battery charging
Discharging power	0 W	0		no battery discharging
Standby power	0 W	0		no standby draw
Self-consumption	0 W	0		nothing consumed
Metering imbalanceok	0 W	0		readings reconcile exactly
Home base load	0 W	0		unmetered remainder of consumption

Ribbon widths are watts in every view. Hover, focus or tap a ribbon to see the sensor behind it.

Zero gross

PV export · snapshot 03

The grid exports while nothing is producing — an impossible meter set that must not divide by zero.

Reading	W	Of gross	Share	Made of
Gross power	0 W	—		no source delivers anything
Grid import	0 W	—		nothing drawn from the grid
Grid export	500 W	—		nothing exported
PV production	0 W	—		pv1 0 W
Charging power	0 W	—		no battery charging
Discharging power	0 W	—		no battery discharging
Standby power	0 W	—		no standby draw
Self-consumption	0 W	—		nothing consumed
Metering imbalanceunexplained	500 W	—		metered sinks drew more than the sources supplied; the engine balances the readings
Home base load	0 W	—		unmetered remainder of consumption

Idle: pv1 · 0 W 500 W of the readings is not explained by the other meters (hatched); the ribbons follow the engine's balanced flows.Ribbon widths are watts in every view. Hover, focus or tap a ribbon to see the sensor behind it.

Why this case exists

Nothing is added here. The same two devices are wired the same way, with one configuration flag flipped, and that is the point — the whole export family turns on a permission rather than on a device.

Reversing the grid changes its kind, not just its sign. An importing grid is the largest source in the house; the same grid exporting is a sink, and the diagram moves it to the other side accordingly. Everything downstream follows from that one reclassification: the export channel takes a share of gross power, the compensation is credited to whichever sources fed it, and self-consumption is measured against what stayed home rather than against everything produced.

The last snapshot is a guard rather than a scenario. The grid exports 500 W while nothing at all is producing — a meter set that cannot physically happen, but that a dropped sensor or a bad scaling factor will hand the engine anyway. Gross power is exactly zero, and every ratio derived from it has to survive being asked.