Captive load

The same three devices, with the consumer now restricted to the PV system. This is the smallest wiring in which a restriction can be honoured at all — and the smallest in which one can fail, which is where the restriction deficit is first published.

What this case shows

• A restricted sink is served from its allowed sources before anything unrestricted shares them.
• Serving the captive sink first pushes the unrestricted base load onto the grid.
• A draw the allowed sources cannot cover is still attributed, and the shortfall is reported as a restriction deficit.

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

Captive load

Captive load · snapshot 01

pv1 makes more than cons1 draws, so cons1 runs on solar alone and the base load is pushed onto the grid.

Reading	W	Of gross	Share	Made of
Gross power	1400 W	1		grid 800 W · pv1 600 W
Grid import	800 W	4/7		grid 800 W
Grid export	0 W	0		nothing exported
PV production	600 W	3/7		pv1 600 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	1400 W	1		grid 800 W · pv1 600 W
Metering imbalanceok	0 W	0		readings reconcile exactly
Home base load	900 W	9/14		unmetered remainder of consumption

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

Load exceeds supply

Captive load · snapshot 02

cons1 draws 500 W but pv1 makes only 300 W: the missing 200 W came from a source it is not allowed to use.

Reading	W	Of gross	Share	Made of
Gross power	1100 W	1		grid 800 W · pv1 300 W
Grid import	800 W	8/11		grid 800 W
Grid export	0 W	0		nothing exported
PV production	300 W	3/11		pv1 300 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	1100 W	1		grid 800 W · pv1 300 W
Metering imbalanceok	0 W	0		readings reconcile exactly
Home base load	600 W	6/11		unmetered remainder of consumption

▲ a restriction is relaxed: the readings cannot be met without it.Ribbon widths are watts in every view. Hover, focus or tap a ribbon to see the sensor behind it.

Why this case exists

Three adapters is the smallest wiring in which a restriction can be honoured, and — one reading later — the smallest in which one can fail. Both belong here rather than further up the ladder, because with three devices you can follow every watt of the deficit by eye.

When the PV system covers the captive load, the rule is visible in one line: cons1 runs on solar alone, and the unrestricted base load is pushed onto the grid to make room. A naive implementation that shared each source in proportion would hand cons1 a slice of grid power it is not permitted to touch, and give the base load solar it has no priority claim to. The two implementations separate immediately.

The second snapshot asks what happens when the restriction is simply not true. cons1 draws 500 W and its only permitted source makes 300 W. The engine does not refuse to answer and does not silently pretend the extra 200 W was solar — it attributes the draw as the meters actually show it and reports the 200 W as a restriction deficit. That figure is not an engine failure. It is the engine saying the meters disagree with how you told it your energy manager behaves.