goodwe-addon/goodwe_controller/DOCS.md

GoodWe RS485 Controller

Drives a GoodWe ES/BP battery inverter over its RS485 meter bus: holds net grid exchange at zero, and runs a monthly battery maintenance cycle so the BMS can balance cells and recalibrate its coulomb counter.

Installers: read FIELD-GUIDE.md in the repository. It is not optional reading — it contains the commissioning gates and the failure modes.

Before you start

You need:

• A GoodWe ES / BP family inverter (AA55 / RS485 meter-bus generation)
• The vendor's meter-emulating controller disconnected from the bus
• A T-CAN485 (ESP32) flashed with firmware/goodwe-master.yaml
• A grid-power sensor already working in Home Assistant, updating every ~5–10 s

The safety model, in short

The inverter holds its last command forever — it has no meter-timeout. So:

• The ESP32 commands 0 W if this add-on stops refreshing for ~30 s, and keeps commanding it.
• This add-on commands 0 W when its inputs go missing, when you stop control, and when it shuts down.
• This add-on commands 0 W and latches there if what it is commanding and what the meter reads point opposite ways for three minutes — see "The sign-disagreement failsafe" below.
• The optional RS485 e-stop is the only thing that covers this machine dying. Without it, a failed host leaves the battery latched at its last command until someone intervenes.
• This add-on raises an alarm — and nothing more — when the meter keeps answering with a reading that never changes while the command sits at the rail. See "The frozen-meter alarm" and, before you rely on it, "Capacity-tariff exposure of the grid-following loop".

If anything looks wrong: stop the add-on. That commands 0 W and the hardware holds it there.

Configuration

Sources

option	required	meaning
meter_entity	yes	Net grid power. Positive must mean importing
meter_invert		Flip the sign if the meter reports the other way
soc_entity	yes	Battery state of charge — use the ESP32's own read
batt_entity	yes	Battery power — again the ESP32's read, + = discharging
batt_invert		Flip if needed
setpoint_entity	yes	The ESPHome number.*_goodwe_setpoint_w

Use the ESP32's readings rather than the inverter's cloud or dongle sensors: those serve cached values, and a stale reading here ends the maintenance charge phase having charged nothing.

P1 meter ingestion

meter_entity above expects one signed sensor, which usually means a template someone wrote by hand. Setting meter_source moves the whole derivation into the add-on, where it is done once and tested, and replaces meter_entity entirely.

Which mode you want depends on what your P1 reader publishes, and there are two shapes in the wild:

• Two unsigned registers, consumption and injection, which is what a Belgian P1 read over DSMR gives you → ha_dsmr, or mqtt_p1 for a bridge. The add-on subtracts them.
• One signed figure, positive = import and negative = export, which is what a HomeWizard P1 gives you (sensor.p1_meter_active_power) → ha_signed. The add-on splits it. ha_dsmr cannot read this: it wants two registers and rejects a negative one outright, which is every exporting telegram.

Either way, do not build the missing shape out of template sensors. The point of meter_source is that the sign convention is derived in one tested place rather than in YAML nobody reviews underneath a safety input.

✅ If your meter is a HomeWizard P1, use homewizard_local, not ha_signed. It reads the same meter and produces the same numbers, but it polls the meter directly instead of watching a Home Assistant entity — and that is the difference between an age sensor a watchdog can threshold and one it cannot. See "sensor.p1_sample_age_s" below; ha_signed remains for installs where the meter is only reachable through Home Assistant.

⚠️ ha_dsmr and mqtt_p1 have never processed a telegram from real hardware. No meter in this installation uses either one. Both were written to the assumption in specs.md §5.2 that a Belgian P1 exposes two unsigned registers, and the meter actually fitted here does not — it is the HomeWizard P1 that ha_signed reads. They are covered by the unit checks in test_p1.py and by an end-to-end test against a fake Home Assistant, and nothing more.

This is recorded because the realistic way it bites is someone debugging a meter problem months from now treating those two paths as proven and looking for the fault elsewhere. If you are the first person to point one at a real meter, expect to find something, and please update this note when you do.

option	default	meaning
meter_source	off	off keeps meter_entity. ha_dsmr subscribes to the DSMR integration over the HA WebSocket; mqtt_p1 reads a topic; ha_signed subscribes to one signed entity over the HA WebSocket; homewizard_local polls a HomeWizard P1's own local API, bypassing Home Assistant
meter_phases	1	1 or 3. Must match the telegram, or every telegram is rejected and logged
meter_max_age_s	30	Beyond this the reading is stale and grid power reads as missing. On its own it does not command 0 W — see the timing note below. It is also the longest a reading is held forward into the 15-minute average
meter_poll_s	5	homewizard_local only. Seconds between polls. Must be well under meter_max_age_s — see below
p1_host		homewizard_local only. The meter's own address, host or host:port (e.g. 192.168.2.250)
meter_mqtt_topic		mqtt_p1 only
p1_import_entity		The unsigned consumption sensor. Do not point this at a signed template
p1_export_entity		The unsigned injection sensor
p1_phase_import_entities	[]	L1..L3, in order. Needed for the capacity-tariff peak on a three-phase connection
p1_phase_export_entities	[]	L1..L3, in order
p1_net_entity		ha_signed only. The signed net-power sensor: + import, - export
p1_phase_net_entities	[]	ha_signed only. L1..L3, in order, each signed the same way. Needed for the capacity-tariff peak on a three-phase connection. The list length must equal meter_phases

Both per-phase lists are checked against meter_phases once at startup: a list of the wrong length disables P1 ingestion with an error in the log, rather than letting every telegram fail its phase-count check one at a time. Leaving the list empty is fine and is not an error — you simply get no per-phase figures, and therefore no capacity-tariff peak. On a three-phase connection that is a much bigger omission than it looks: on a surveyed reading here the phases carried 2769 W of import while the connection netted 187 W, so the billed quantity is understated roughly fifteenfold if the phases are missing.

How long a dead meter takes to reach 0 W

meter_max_age_s and stale_input_s stack. They are two different clocks and neither one is the whole answer:

step	option	default
telegrams stop, P1 sample goes stale, grid power starts reading missing	meter_max_age_s	30 s
inputs have been missing long enough for the loop to command 0 W	stale_input_s	15 s
total, meter death → 0 W commanded by this add-on		45 s

So in P1 mode stale_input_s is not "how long inputs may be missing before commanding 0 W" measured from the meter dying — it is measured from the moment the P1 sample already went stale. Size the pair together: the ESP32's own watchdog commands 0 W after ~30 s of silence from this add-on regardless, and that layer is unaffected by either option.

There is no fallback to an inverter-side power figure, deliberately. The inverter's own AC power tracks its battery almost perfectly and the real meter hardly at all, so a controller that failed over to it would be regulating against its own output while looking healthy.

The mqtt_p1 payload is one JSON object per telegram, and the schema is strict — a key it does not recognise is a telegram from something other than what was tested, and guessing a key here means guessing a kilowatt:

{"import_w": 1234.0,
 "export_w": 0.0,
 "phases": [{"import_w": 500, "export_w": 0},
            {"import_w": 400, "export_w": 0},
            {"import_w": 334, "export_w": 0}],
 "timestamp": "2026-08-24T18:00:05+02:00"}

phases and timestamp are optional; timestamp must carry a UTC offset. Where it is present it is used for the age, which is what stops a retained message replayed on reconnect from presenting a ten-minute-old reading as current.

homewizard_local — polling the meter instead of Home Assistant

Set p1_host to the meter's address and the add-on does GET /api/v1/data on it every meter_poll_s seconds, reading active_power_w (signed, same convention as ha_signed) and the three active_power_l{1,2,3}_w fields. Home Assistant is not involved: no entity, no WebSocket, no integration to mis-configure. Per-phase figures are used only when the meter serves all meter_phases of them — a single-phase meter returns null for L2/L3, and the connection-level reading is still accepted on its own.

Why this mode exists: every HTTP response is an arrival. The meter answered, now, with its current reading — whether or not the number moved. That is the signal sensor.p1_sample_age_s needs and the one Home Assistant cannot give it at all (see the note below). It is also simply fewer moving parts: the five-second cadence is the meter's own, rather than an integration's polling of it re-published as a state change.

Cadence. The age is never fresher than the poll interval, so:

meter's own update rate	~5.0 s (measured 4.97 s)
meter_poll_s default	5 s — nothing to gain below the meter's own rate
meter_max_age_s default	30 s, i.e. six polls of headroom
meter_poll_s >= meter_max_age_s	refused at startup — every reading would be stale before its successor arrived
meter_poll_s > meter_max_age_s / 2	warned — one missed poll makes the reading stale

A failed poll — timeout, connection refused, non-200, unparseable body — is a missing reading. It submits nothing, so the reading does not become 0 W, the last good value and its timestamp are left alone, and the age goes on climbing. That is exactly what a dead meter should look like.

What it still cannot see: a frozen meter. A meter that answers 200 OK forever with a stale number is arriving, so no arrival detector — this one included — can tell it from a healthy one. The local API does expose the raw material the HA path never had (the total_power_*_kwh registers stop advancing), and the transport tracks it as unchanged_s, but it is deliberately not folded into the age and not thresholded: this controller regulates grid power toward ~0 W, and at a converged −10 W the export register needs six minutes to move by its 1 Wh resolution while the power figure legitimately repeats. Thresholding that at 30 s would rebuild the false-trip limit cycle at the exact operating point the controller aims for. Freeze detection is a separate problem and needs the low-power case solved first.

You read it yourself instead: the add-on's status page shows it on the P1 line, as … 4 rejected, measurement unchanged for 312 s. On a house drawing real power that figure stays in the seconds; minutes of it while the load is clearly not near zero is the meter to go and look at.

sensor.p1_sample_age_s

Published over MQTT discovery whenever a broker is available: seconds since the newest accepted telegram, refreshed every second rather than only when a telegram lands. The ESP32's stale-input watchdog subscribes to this exact entity id, so do not rename it.

The reason it is recomputed against the clock is that Home Assistant only pushes a state when the state changes. A meter sitting at a genuinely constant reading emits nothing, which is indistinguishable — to anything watching the value — from a meter that has died. Watching the age instead separates the two: it climbs when telegrams stop and resets when they arrive, whatever the reading says.

The entity is only created when meter_source is not off. With P1 ingestion disabled there is nothing feeding it, and an age sensor climbing with no ingester behind it would trip the firmware watchdog on a system that is working fine.

Known limit, mqtt_p1. The age measures arrival. On the MQTT path a bridge that is stuck republishing its last telegram keeps arriving, so the age stays near zero and a frozen meter still looks fresh. Detecting that needs a change-detector rather than an arrival-detector, and it is not in this version.

⚠️ Known limit, ha_signed — do not drive a watchdog off this age yet. On the HA WebSocket paths the age is stamped when a state_changed arrives, which means it measures time since the value last changed, not time since the meter last reported. Home Assistant offers nothing better: a repeated reading produces no state_changed, does not advance last_reported on either the REST or the WebSocket serialiser, and state_reported cannot be subscribed to over the WebSocket at all (Event filter is required for event state_reported). All three measured on the ENV-01 rig against the real HomeWizard integration with the meter frozen: 0 state_changed in 70 s and no timestamp movement anywhere.

ha_dsmr mostly escapes this because a DSMR telegram updates several entities and something in the set almost always moves. ha_signed has exactly one entity, so a healthy meter under a flat load is indistinguishable from a dead one. This is not hypothetical: in our own captures (sim/scenarios/ha-p1_meter_active_power-2026-08-20.json) the real house meter went 42.2 s and 97.0 s between changes, and 23 Aug peaks at 29.1 s — all past the default meter_max_age_s of 30.

So sensor.p1_sample_age_s on ha_signed is safe to read, and it is correct whenever the value is moving, but it must not yet be thresholded by the ESP32 stale-input watchdog: a quiet house would trip the battery to 0 W. Raising meter_max_age_s is not the fix — the two conditions produce an identical signal, so a bigger number only chooses which of the two errors you get. The real fix is an arrival stamp the meter itself provides — and that now exists: meter_source: homewizard_local. If you have a HomeWizard P1, switch to it. If your meter is only reachable through Home Assistant, this limit still applies to you and the watchdog threshold still must not be armed.

Where the age is trustworthy:

mode	the age measures	safe to threshold from firmware
homewizard_local	time since the meter answered	yes — every HTTP response is an arrival
ha_dsmr	time since one of several entities changed	no — statistically usually fine, which is a masked bug, not an absent one
ha_signed	time since the one entity changed	no — see above
mqtt_p1	time since a message arrived	arrivals yes, but a stuck bridge republishing keeps arriving

Control

option	default	meaning
max_w	2000	Hard limit on what may be commanded. Start low, raise after commissioning
gain	0.6	Correction per cycle. At the limit — do not raise
slew_w	1000	Maximum change per cycle
deadband_w	15	Ignore errors smaller than this
target_grid_w	-10	What the meter should rest at. Negative = a slight export
step_w	10	Quantisation
saturation_w	500	Divergence that counts as "the inverter is at a limit"
saturation_cycles	3	How many consecutive cycles before freezing. A cycle is one meter update or cycle_floor_s, whichever comes first - see the note below. Do not set to 1
integrator_max_w	0	Bound on the loop's accumulator, and 0 means "same as max_w". Caps how much stale error can be waiting to unwind when the sign flips. Do not raise it above max_w - the output clamp already bounds what is commanded, so the only thing extra headroom buys is more cycles of wrong-direction power after every saturation event. Lowering it below max_w is the useful direction
heartbeat_s	10	Refresh interval; must stay well under the firmware watchdog
cycle_floor_s	15	The longest the loop may go without evaluating. A deadline on the gap between cycles, reset by every cycle — on a healthy meter it never elapses and changes nothing. Raise it only if your meter is slower than ~10 s; it must stay under meter_max_age_s, past which there is no reading to evaluate anyway
stale_input_s	15	How long inputs may be missing before commanding 0 W. In P1 mode this clock starts only after meter_max_age_s has already expired — the two stack, see "How long a dead meter takes to reach 0 W"
auto_start	false	Start controlling on boot (only after commissioning)
sign_disagree_w	300	Both the command and the meter must exceed this before a sign difference counts. Must stay below max_w or the watchdog can never fire, and the add-on refuses to start
sign_disagree_s	180	How long they must stay opposed, continuously, before the failsafe trips

The sign-disagreement failsafe

If the setpoint this add-on is emitting and the grid figure it is regulating on point opposite ways — charging the battery while the house imports, or discharging it while the house exports — with both over sign_disagree_w, for sign_disagree_s continuously, the add-on commands 0 W and holds it there. The banner reads FAILSAFE, the commissioning list says which two numbers disagreed and for how long, and the Controller status entity reports failsafe.

It does not clear itself, and restarting the add-on does not clear it either. Pressing Start / stop control twice — stop, then start — is the only thing that does. That is deliberate on both counts:

• Commanding 0 W removes the command side of the comparison, so the disagreement always vanishes the instant the trip works. A watchdog that took that as proof the fault was over would hand the inverter straight back to the loop that was driving the wrong way, three minutes later, forever.
• The trip is written to /data/state.json and restored on startup. Restarting the add-on is the first thing most people try when they see a red banner, and a latch that a restart clears would bring the controller back armed, into the same fault, unattended — and under a Supervisor that restarts a crashed add-on automatically, would do so in a loop. After a restart the banner, the 0 W and the recorded reason are all still there.

What it is for. This is a loop-integrity check: it asks whether the loop's output direction still matches the input state it was regulating. It catches a polarity error anywhere between the meter and the wire, and an integrator so far wound up that unwinding takes minutes. It is the check that would have caught all four episodes of 2026-08-20, when a commercial controller charged the battery out of the grid, four times, for up to 77 minutes at a time.

What it is not for. It does not detect an inverter that acts opposite to what it was told — that moves the meter further the same way, so command and meter agree while everything runs away. That is the saturation freeze's job (saturation_w / saturation_cycles), which compares the command against the battery's actual power. The two checks are complementary and neither replaces the other.

Why it will not false-trip on ordinary operation. A battery that refuses a command (empty, full, standby) leaves the meter where it was, so command and meter agree. A frozen meter drives the loop into agreeing with it. Around the resting point both signals are inside the 300 W gate, so the deadband can never produce one. A load step does flip the meter's sign before the loop catches up — measured on a full captured day, the longest such crossing is 30 s, against a 180 s window. And the watchdog is disarmed whenever the grid-following loop is not what is driving: a maintenance grid charge opposes the meter by design and must not be mistaken for a fault.

Both numbers are measured rather than chosen, and are exposed only because the ticket requires defaults rather than constants. On the captured healthy day sign agreement is 93.4 %; on the four captured fault clusters it is 0.3 %, 0.9 %, 10.5 % and 0.0 %. There is no reason to move either value without a capture that says so.

Saturation is counted in cycles, not seconds

The specification states the saturation window as "> 10 s". This add-on counts cycles instead, and that is a deliberate, accepted deviation rather than an oversight - the acceptance criterion is not met as literally written.

A cycle here is one meter update or cycle_floor_s elapsing, whichever comes first. At the reference P1's ~5 s update rate the default of 3 cycles is usually around 15 s, and the worst case is bounded at 3 x cycle_floor_s = 45 s. It is still not the 10 s the specification asks for, so the deviation stands - but it is now a bounded number rather than an open one.

⚠️ This passage used to say something different, and the second half of it was wrong. Until SAFETY-12 the loop ran only when the meter value changed, so a meter that repeated a value stalled the counter for as long as it repeated, with no upper bound at all. That was defended here on the grounds that "a stalled counter is a detection-latency limit and not a runaway risk - the condition that stalls it stops the whole loop, so nothing accumulates while it is stalled". That argument covers integrator windup and nothing else. The hazard it misses is staleness: while the loop was stopped the heartbeat kept re-emitting the last command and the firmware kept putting it on the wire every 2 s, so a command computed from an old reading went on being executed through a real load change, with every indicator reading healthy. Measured on the rig during TEL-05: 70 s at a literally constant 350.0 W, 14 arrivals, zero control cycles.

The half that survives is the first one: the control law is still a pure function with no clock, and the wall-clock window still lives in Controller, which has one - see run_control(). What changed is that the controller now enforces a floor on the gap between cycles, so saturation_cycles finally means a bounded number of seconds.

If a tighter window matters on your site, lower cycle_floor_s (not below your meter's update interval, or the floor starts firing on a healthy meter) or raise saturation_cycles for a fast meter.

This is not a freeze detector, and it deliberately cannot be one. Nothing here decides whether a repeated reading is true — see unchanged_s in the meter section for why no threshold on that is safe at the converged operating point. The floor only stops "the number is the same" from meaning "do not think". The consequence is worth stating plainly: against a meter that is genuinely frozen at a wrong value, the loop will now correct toward that wrong value instead of holding a stale command. It is bounded by max_w, the arbiter and the device rating, and it is the same thing that already happened to a lying meter whose value merely jittered — bit-exact repetition was never a safety property.

Why target_grid_w is not zero

The deadband is a one-way ratchet: any resting point inside it holds until something disturbs it. Import and export are separate registers on the meter, so a rest point of +14 W is billed for every second it holds and no amount of export cancels it - 14 W all day is 0.34 kWh.

Biasing the target below zero moves that residue into the export register, which is not billed. The resting band becomes target ± deadband, so:

target_grid_w	resting band	worst billed leak	export given away
0	-15 … +15 W	~15 W (0.35 kWh/day)	none
-10	-25 … +5 W	~5 W (0.12 kWh/day)	~10 W
-15	-30 … 0 W	none	~15 W (0.36 kWh/day)

Set it to -deadband_w if injection is worth nothing to you and you would rather give the energy away than buy it back. Set it to 0 if you are paid properly for export, or if you are debugging and want the loop centred.

⚠️ This is a billing knob, not a speed knob. If import is arriving in bursts rather than as a trickle, the cause is tracking lag, and this will not help - see "Why the tuning is what it is".

Maintenance

option	default	meaning
maintenance_enabled	false	Enable the monthly cycle
maintenance_interval_days	28	Minimum gap between cycles
maintenance_start_hour	10	Hour of day a due cycle begins
maintenance_discharge_w	2000	Drain rate (exports the surplus). Above max_w it is clamped to max_w — the drain phase SETs the setpoint and the arbiter bounds it, saying so on the status page (limited by supervised(max_w)). Warned about, not refused: the cycle still completes, just slower
maintenance_charge_w	2000	Charge ceiling, capped again by peak headroom. Must stay at or below max_w or the cheap-window shaping (hi = -maintenance_charge_w) contradicts the supervised limit (lo = -max_w), the arbiter resolves it to 0 W, and maintenance silently never charges in a cheap window — the add-on refuses to start
maintenance_soc_floor	11	Drain target — stay just above the inverter's own floor
maintenance_soc_target	99	Charge target
maintenance_hold_min	120	Hold at full so the BMS can balance

Tariff (all optional)

option	meaning
peak_forecast_entity	Quarter-hour demand forecast, for capacity-tariff markets. Empty = no cap
peak_cap_w	The site's capacity-tariff target
price_now_entity, price_avg_entity	Dynamic tariff. Empty = never force a paid grid top-up

On a capacity-tariff site the maintenance charge is capped by the headroom left under peak_cap_w, and if the forecast goes over the cap the charge-only clamp is dropped so the battery can shave the peak instead. Money outranks the maintenance schedule.

Capacity-tariff exposure of the grid-following loop

⚠️ This section described the exposure BEFORE SAFETY-07. The loop is now capped — see "The capacity-peak guard" below — and what follows is kept because it is still the clearest statement of WHAT is being guarded and why the number is worth what it is.

⚠️ peak_cap_w caps MAINTENANCE charging. It does not cap the loop. The grid-following loop is bounded by max_w and by the device rating, and by nothing else. That is deliberate — the loop exists to reduce what crosses the meter, so under every healthy condition it lowers the peak rather than raising it — but it means one thing is true and worth writing down:

If the meter lies, the loop will happily buy max_w from the grid for as long as the lie lasts, and no cap in this add-on stops it. A meter frozen at a large export reads as "the house is exporting hard", the loop charges the battery to correct it, and the correction is a grid import. At the schema maximum max_w: 5000 — which is what this house runs, and is also the device rating — that is a 5 kW unattended import.

The bill is not the energy. In the Belgian capaciteitstarief the month is billed on its highest quarter-hour average, so fifteen minutes of this sets the whole month's peak. A measured case: one 4998 W quarter moved a monthly peak from 4832 W to 5013 W, and every day of that month was billed at the higher figure.

What exists today, and what does not:

max_w bounds the magnitude	✅ — but the exposure IS the magnitude
Maintenance charging capped under peak_cap_w	✅
Loop capped under peak_cap_w	✅ — SAFETY-07, on every meter_source but off
Frozen meter detected	✅ on homewizard_local only, alarm only
Frozen meter stopped	✅ — SAFETY-07 forbids importing while the meter is frozen
SoC guard on the loop	❌ — the BMS is the only energy backstop

On the legacy meter_source: off path there are no P1 telegrams, so there is no quarter-hour average to guard, and the status page says NOT COVERED. There the mitigation is still operational: set max_w no higher than the loop actually needs (the tuning was measured at 2000 W and a 1.78 kW load step is tracked fine there), fit the e-stop, and watch for the alarm.

The capacity-peak guard

What it does. Every cycle the add-on projects the open quarter to its end-of-interval average — from P1 telegrams only, never from the command — and compares it to a ceiling. Over the ceiling it files one claim: a lower bound on the setpoint, at P_PEAK. That single shape is both behaviours §10.1 asks for: a hard clamp on charging while the bound sits above the standing charge, and pre-emptive discharge while it sits above zero. It can never cap discharge or export, because a floor cannot.

The number. excess = 900 × (projected − ceiling) ÷ seconds remaining, and the floor is the measured battery power plus that. The 900/remaining factor is the design rather than an accident: it is 1.0 at the top of the quarter and grows, so the guard is gentlest when its projection rests on the least evidence and becomes aggressive only once the quarter is nearly measured.

The ceiling is peak_cap_w, raised to the month's banked peak when that already stands higher — once a month's bill is set at 5013 W, holding later quarters to 3500 W buys nothing and costs real charging. That relaxation is granted only by an OBSERVED reading: a peak store that cannot be read leaves the ceiling at the cap, so a broken instrument makes the guard stricter, never looser.

When it cannot see, it forbids importing. Three states are not evidence and are checked before the projection is graded: no open quarter (a fresh averager projects a confident 0 W, which is under every ceiling there is), a meter gap longer than meter_max_age_s, and SAFETY-18's frozen-meter conjunction. In all three the claim becomes a floor of 0 W. That is the backstop for the frozen meter: the alarm arrives at meter_freeze_s (300 s) of a 900 s billing quarter and commands nothing, and this stops the import.

It trips, where the freeze detector only notifies, and the captures are why. On the healthy reference day (2026-08-23) it engages on zero of 95 quarters. The action is level-triggered and unlatched — re-derived from a fresh projection every cycle, released the instant the projection drops back — so a false engagement costs one cycle of discharge rather than a parked battery. And it is a LIMIT, so every stop in the watchdog table still outranks it.

Replayed on 2026-08-20, the day the vendor controller failed: the billed quarter measured 5029.8 W, above the inverter's own 5000 W rating, and the guard brings it to 3485 W — under the soft limit, without ever asking for more than the inverter can give. Across both committed days the quarters under the limit go from 189/190 to 190/190. Two days is not thirty and does not close AC 3; it is the comparison two days can support.

What it alarms on is saturation, not engagement. An engagement is an ordinary control action and goes to the action log and the status page. A saturated guard — asking for everything the inverter has while the quarter is still projected over — raises one notification (goodwe_peak_saturated), because that is the one state where the money will be spent and shedding load is the only thing left that changes the bill.

No new option. The ceiling is peak_cap_w, which already shipped. The coverage threshold is meter_max_age_s, the freeze predicate is meter_freeze_s, and the achievable discharge comes from max_w and the device rating — every one of them a key that already exists.

The winding-loop alarm (the output clamp)

Every setpoint this add-on writes is clamped to max_w before it leaves the process, and when that clamp actually engages, it alarms. The clamp on its own is not the feature - this project already clipped, and the clipping is what hid the defect the guard exists for: with the inverter switched off entirely an unclamped integrator climbed ~130 W per 4 s past 10 kW and, pinned at the 5 kW rail, reported 14 768 W. Clipped silently, that is a flat, legal-looking 5000 W hold on every dashboard, and nothing anywhere says the loop asked for three times it.

What "the rating" is. The bound is max_w, and only max_w. It is already validated against the setpoint device's own range at startup - the add-on refuses to start if max_w exceeds what the device accepts (and again once ESPHome is up and the real rating is known), so by the time the loop runs the two numbers agree. The device range is applied a second time inside the write as defence in depth; after a successful validation it cannot bite, and if it ever does, that engagement alarms too and names the bound.

Clamping is not saturation, and the two never share a channel.

	what it means	what happens
clamp	the computed value exceeded the rating	a software bug signal - something upstream is winding. Alarm.
saturation	the inverter is not following a perfectly legal command	a hardware condition - freeze the integrator. No alarm.

A loop can be legally saturated all day: a cold pack, a curtailed inverter, an export limit. Routing the clamp through a saturation-shaped alarm puts the bug signal inside the noise, which is the same silence as clipping quietly. They share no reason code, no notification id, no status row and no counter.

It is an alarm, not a trip. The clamped value is written and the loop keeps running - this is not the sign-disagreement failsafe, which commands 0 W. You get a persistent notification (goodwe_output_clamp, replaced rather than stacked), an ERROR in the log with the reason code OUTPUT_CLAMP, a row in the event list, and a red status banner while it is engaged. Once it clears, a warning row keeps the engagement count so the evidence does not vanish with the condition. Consecutive engagements share one event row carrying the exact count, because the event list keeps only 40 rows and a row per cycle would flush every other guard's entries out of it.

There is nothing to configure, deliberately. The bound is max_w, which you already set; giving the guard a limit of its own would be a second number that can disagree with the first, which is exactly the failure the startup validation exists to prevent. The alarm's cadence - first engagement, then re-asserted every 30 s while it persists, cleared after 3 clean cycles - is fixed for the same reason RAIL_FRAC is: it describes the notification bus, not the plant.

WARNING: on a default install the engagement you will see is the integrator's, not the output's. The control law bounds the integrator to max_w and then derives the command from it, so the command itself can never come out over the rating unless integrator_max_w has been deliberately raised above max_w. Both are watched. A guard that watched only the emitted value would be silent on every standard configuration.

The frozen-meter alarm

A meter that has died is easy — it stops answering, the sample age climbs past meter_max_age_s, the reading becomes missing, and the add-on and the ESP32 both command 0 W. A meter that keeps answering 200 OK with a document that never changes is the hard one: every freshness mechanism in the stack reads it as healthy, because it really is arriving on every poll. The loop then integrates a constant error and winds to the rail, in 75–360 s at max_w: 5000.

The add-on alarms when both of these are true at once:

• the meter's own document (power figure and both kWh registers) has not changed for meter_freeze_s — 300 s by default; and
• the command standing on the wire is at the rail, within 5 % of max_w.

Neither half is usable alone. A bare "unchanged for N seconds" rule false-trips at the exact operating point this controller aims for — at a converged −10 W a 1 Wh register legitimately takes about six minutes to move — and a bare "at the rail" rule fires on any genuinely large load. Together they are safe in both directions, because a real railed condition means kilowatts still crossing the meter, and a kilowatt advances a 1 Wh register every 3.6 s.

It is an alarm and nothing else. It does not command 0 W, does not latch, and does not claim the actuator. A false trip here parks the battery; a false notification costs an alert. Turning it into a trip is a separate decision that needs data from a real install — and an answer to "what should the loop do instead", given that 0 W is itself an import of whatever the house is drawing.

When it fires you get a Home Assistant persistent notification (goodwe_meter_frozen, replaced rather than stacked on a repeat), an ERROR in the add-on log, an entry in the UI's event list, and a red banner on the status page. The loop keeps running. If the meter really is stuck, stop control from the add-on UI.

⚠️ Only meter_source: homewizard_local is covered. It is the only transport that reads the meter's own document; on ha_dsmr, mqtt_p1, ha_signed and off there is no signal to threshold and the status page says NOT COVERED rather than pretending the guard is armed.

option	default	meaning
meter_freeze_s	300	Seconds of an unchanged measurement, while the command is at the rail, before the alarm

Why 300 s: over 2399 s of this house at the converged operating point (mean grid −14.2 W, 1194 polls, 735 of them repeating the previous reading) the largest unchanged_s any sample sees is 8.0 s, and the longest interval serving no distinct reading at all is 15.4 s. There is also a structural reason not to lower it much: at 300 s the slowest a healthy register can tick and still look unchanged is 12 W, which is inside the 15 W deadband — so the command there is parked at 0 W and the two halves of the rule cannot both be true. At the schema floor of 60 s that figure is 60 W and only the margin is left.

Site

option	meaning
estop_fitted	Whether the RS485 e-stop is installed. Drives the warning banner
log_level	trace/debug/info/warning/error

The Web UI

The ingress panel shows live values, why the controller is commanding what it is, and a Commissioning checklist that names any problem in words. It also carries the three buttons: start/stop control, force a maintenance cycle, and abort one.

Status entities

If an MQTT broker is available the add-on publishes setpoint, grid power, battery power, state of charge, maintenance phase and controller status by MQTT discovery. This is observability only — the controller works fine without a broker, and MQTT problems can never affect control.