Where the power comes from
How Power Insight decides which source powers what: the flow channels behind the ratio and share sensors, and the rules that decide a battery's or consumer's source mix. For the short version, see How it works.
The four channels
Gross power leaves the system through exactly four channels. Each channel has a natural sink — the device type that receives that power:
| Abbrev | Channel | Sink device | Sensor wording |
|---|---|---|---|
| EXP | Export | Grid | … to grid |
| CON | Self-consumption | Consumers (loads) | … to home consumption |
| CHG | Charging | Batteries | … to batteries |
| STB | Standby | PV systems (their own night draw) | … to system standby |
"System standby" is the idle draw of the energy system's own equipment — not household appliances on standby, which count as home consumption.
Every provider — the devices that feed gross power (grid import, PV production, battery discharge) — expresses its relationship to a channel two ways, alongside its power in Watts (Production to home consumption):
- ratio — of this provider's own output, the fraction going to the
channel (
channel_power ÷ provider_output) — Production to home consumption ratio. - share — of the whole channel's power, the fraction this provider
supplied (
provider_contribution ÷ channel_total) — Share of home consumption.
Not every provider feeds every channel. The grid cannot export to itself, so it
has no EXP sensors; otherwise each provider carries a _ratio and a _share
for each channel it can feed:
| Provider | EXP | CON | CHG | STB |
|---|---|---|---|---|
| Grid | — | ✓ | ✓ | ✓ |
| PV | ✓ | ✓ | ✓ | ✓ |
| Battery | ✓ | ✓ | ✓ | ✓ |
CHG is the only channel with explicit routing (a battery's Charges from list), so it has two complementary sensor families — don't confuse them:
- the provider-side aggregate Share of battery charging ("X % of all charging in the home is supplied by the grid"), on the grid/PV/battery device; and
- the sink-side per-source breakdown Charging share from <source> ("X % of this battery's charging comes from the grid"), on the battery — see Charging-source attribution.
CHG sensors on a provider only appear when that provider is actually a configured charge source for some battery; STB, having no routing, is attributed to providers in proportion to their share of gross power.
Charging-source attribution
When a battery charges, its stored energy comes from some mix of the grid and your PV systems — configured in the battery's Charges from list. Power Insight traces that mix in real time to:
- attribute the battery's charging cost to the right source, and
- power the charging source share sensors ("70 % solar, 30 % grid").
The same tracing decides where a smart-plug consumer restricted to specific sources (its Powered by list) draws its power, and how the power you export is sourced.
How the mix is decided
Your local generation — solar production and battery discharge — is limited, and while you are importing from the grid it is the scarce, cheaper resource. Power Insight hands it out in a fixed priority order, and the grid fills whatever is left over:
- Locked devices first. A battery set to charge from solar only, or a smart plug that runs on excess solar, has no fallback — so it gets first claim on its allowed local sources.
- Your home base load next. The always-on household consumption you don't meter directly takes the local power it needs before any flexible device does.
- Flexible devices last. A battery allowed to charge from the grid can fall back on it, so it only receives the local generation the first two steps left behind; the grid covers the rest of its draw.
When you are exporting — your solar is in surplus — local power isn't scarce, so this ordering doesn't apply and every device is simply attributed to the live mix.
Why two devices can show different mixes
Because local generation is allocated in order rather than split evenly, two devices drawing power at the same instant can show different source mixes:
- A battery locked to solar shows 100 % solar while any is available; a battery that can also use the grid, charging at the same moment, may show mostly grid — it receives only the solar the locked battery and your home load didn't take.
- The mix shifts with your household load: the more your home consumes directly, the less local generation reaches a flexible battery, so its grid share rises — even though nothing about the battery itself changed.
- Two PV systems of different sizes show it too: a battery drawing from the larger one keeps more solar (a lower grid share) than one drawing from the smaller, because more of the larger system survives the earlier steps.
Energy lost in a charge/discharge cycle needs no correction here: the battery's charging and discharging are both metered at its AC port, so the losses are already the difference between the two.
When a device draws from outside its sources
The sources you pick under Specific devices describe what you expect your energy manager to do. They are not a hard limit: Power Insight counts every watt your meters report, even when it can't have come from the sources you picked.
So when a device draws more than its allowed sources supply at that moment, the extra is counted as coming from your other sources. The typical case is a battery set to charge from solar only that tops up from the grid at night: with no solar to draw on, its whole charge is counted — and priced — as grid power.
The watts drawn from outside the selection are shown in the
restriction_deficit attribute of the device's Operating cost rate and
Levelized operating cost rate sensors. It reads 0 while the device sticks to
its sources, and exists only on devices set to Specific devices.
A deficit is not necessarily a mistake. A battery that prefers solar but tops up from the grid when its charge runs low is still best set to solar only: with the grid in its list, Power Insight would count its charging as grid power first whenever your home imports. Set to solar only, its charging counts as solar whenever there is solar, and the deficit shows just the grid top-ups — which is what really happened. A deficit that never goes away, on the other hand, usually means the selection no longer matches what your energy manager does; Reconfigure the device.
The precise allocation — the three tiers above and their edge cases — is written up for contributors in Engine calculation decisions.