PV self-consumption

One PV system added to the grid, and nothing restricted. Two sources are enough for the raw proportional mix, for the divergence between what power costs now and what it costs levelized, and for a PV system that is drawing rather than producing.

What this case shows

• An unrestricted sink's provenance row is the raw source mix.
• PV standby is a sink drawing from the mix, not negative production.
• Marginal cost and levelized cost diverge as soon as a local source runs.
• A source that only draws standby makes the saving rate negative.

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

Sunny, partial

PV self-consumption · snapshot 01

Grid and PV system both supplying; the base load takes them in proportion.

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	1400 W	1		unmetered remainder of consumption

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

PV covers all

PV self-consumption · snapshot 02

The PV system covers the house exactly. The grid is present but contributes nothing.

Reading	W	Of gross	Share	Made of
Gross power	600 W	1		pv1 600 W
Grid import	0 W	0		nothing drawn from the grid
Grid export	0 W	0		nothing exported
PV production	600 W	1		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	600 W	1		pv1 600 W
Metering imbalanceok	0 W	0		readings reconcile exactly
Home base load	600 W	1		unmetered remainder of consumption

Idle: grid · 0 WRibbon widths are watts in every view. Hover, focus or tap a ribbon to see the sensor behind it.

PV standby

PV self-consumption · snapshot 03

pv1 draws 20 W standby, so it is a sink served by the grid — and the saving goes negative.

Reading	W	Of gross	Share	Made of
Gross power	1000 W	1		grid 1000 W
Grid import	1000 W	1		grid 1000 W
Grid export	0 W	0		nothing exported
PV production	0 W	0		no PV system
Charging power	0 W	0		no battery charging
Discharging power	0 W	0		no battery discharging
Standby power	20 W	1/50		pv1 20 W
Self-consumption	980 W	49/50		grid 980 W
Metering imbalanceok	0 W	0		readings reconcile exactly
Home base load	980 W	49/50		unmetered remainder of consumption

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

PV unavailable

PV self-consumption · snapshot 04

The PV system's sensor has dropped out; the grid still reads, but the total cannot be trusted.

pv1 has no reading, so the engine publishes no flows for this snapshot.

Reading	W	Of gross	Share	Made of
Gross power	unavailable	—		not published: a reading is unavailable
Grid import	1000 W	—		grid 1000 W
Grid export	0 W	—		nothing exported
PV production	unavailable	—		not published: a reading is unavailable
Charging power	0 W	—		no battery charging
Discharging power	0 W	—		no battery discharging
Standby power	unavailable	—		not published: a reading is unavailable
Self-consumption	unavailable	—		not published: a reading is unavailable
Metering imbalance	unavailable	—		not published: a reading is unavailable
Home base load	unavailable	—		not published: a reading is unavailable

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

Why this case exists

This is the first case with a choice in it. Two sources are supplying one sink, and the engine has to say in what proportion — the answer being the raw availability of the sources, with no restriction anywhere to complicate it. Every restricted case later in the ladder is a departure from exactly this, and if the tiered logic in the solver is working, this is what it must collapse to when there is nothing to tier.

Two sources are also the minimum for the money layer to say anything interesting. With the grid alone, what power costs now and what it costs levelized are the same number. Add a PV system and they come apart: coe falls as the free fuel displaces the tariff, while lcoe carries the PV system's capital cost whether or not the sun is out.

The standby snapshot is the sharpest thing here. A PV system drawing 20 W is not producing −20 W — it is a sink, and it is served from the grid like any other. Which means the saving rate goes negative: at that instant the solar installation is costing its owner money.