This blueprint drives a Hoymiles microinverter (through OpenDTU / OpenDTU-OnBattery) so it delivers what your house is using and doesn’t export to the grid. I built it for a battery-fed setup (48 V LiFePO4 → HM-1200NT), but it works with any inverter that exposes a non-persistent absolute power-limit number entity.
Full build log, Home Assistant package, ESPHome configs and real-world numbers: GitHub - jakeshake/zerospill: Battery-buffered zero-export solar: Hoymiles + OpenDTU-OnBattery + Home Assistant. Feeds only what your house uses, shifts solar into peak TOU hours. DIY build log, not a UL 3700 plug-in kit. · GitHub
How it controls
- Cuts fast when the grid goes negative. It acts immediately on a raw meter reading of more than 150 W export, or on export in a 3-reading median.
- Raises slowly. The target has to stay above the current limit for 20 s, each raise is capped at +400 W, and it waits 30 s between raises. Short load spikes (dryer, kettle) don’t chase the inverter up.
- Waits for settled readings. After each change it ignores grid readings taken before the inverter could respond, so a stale meter value never fakes a load spike or a dip.
- Applies a learned correction factor between the commanded limit and actual AC output.
- Turns the inverter off when the target drops below 40 W, or when the target sensor has been unavailable for 5 minutes.
What you need
- A grid power sensor (W, + import / − export). I use an Emporia Vue Utility Connect flashed with ESPHome. It updates every few seconds and only works with supported smart meters.
- A 3-reading median of that sensor (
filterplatform,median,window_size: 3) - A target power sensor: what the inverter should deliver right now. Usually house load (grid + inverter output) minus a small buffer, plus your own battery/time-of-use rules. The repo’s package has a full version with peak-hour pacing, Solcast-based overnight reserve and SoC floors.
- OpenDTU entities: AC power, non-persistent absolute limit, producing, and the turn-on/turn-off buttons. Don’t use the persistent limit, which writes to the inverter’s flash every time.
- Three helpers:
input_numberlimit correction (0.8–1.4, start at 1.0),input_numbermax power (W), andinput_booleanraise-pending.
Set max power to what your DC side can safely carry. Mine is 1,150 W, which keeps a 48 V bus at about 24 A on a 30 A breaker/fuse.
Results
On sunny late-October days (6 × 200 W panels, 5 kWh battery, SCE TOU-D-5-8PM), solar + battery covered 35–41 % of the house with export effectively zero. The only export is brief spikes of about 1 Wh when the AC compressor shuts off, because the inverter takes a few seconds to apply a new limit. Screenshots are in the repo.
Here’s the Home Energy dashboard from the repo running in the HA companion app (live flow, today’s totals, last 7 days). It’s built to fit a phone with no sideways scrolling:
Please read before copying the hardware
This is not a UL 3700 plug-in (“balcony”) solar kit, and it doesn’t fall under California’s SB 868 or similar plug-in solar laws. My inverter is on a dedicated 240 V circuit and runs from a DIY battery bus. The repo’s Safety & Legal page (docs/safety-and-legal.md) covers what that means, plus the DC gotchas I hit: pre-charging inverter input caps, and reversed polarity when feeding MC4 Y-splitters backwards. The blueprint itself is just control logic and works with any inverter setup.
Blueprint
blueprint:
name: Zero-Export Inverter Controller (OpenDTU / Hoymiles)
description: >
Drives a microinverter's non-persistent power limit to follow a target
sensor without exporting. Cuts fast on export, and raises slowly only after
the target has stayed above the limit for 20 s. It acts only once grid
readings have settled after its last change, and caps each raise at +400 W.
Controller only: you supply the target sensor (house load minus a buffer,
plus your own battery/time rules) and three helpers. The full system with
forecasting is in the repo's package.
https://github.com/jakeshake/zerospill
domain: automation
source_url: https://github.com/jakeshake/zerospill/blob/main/home-assistant/blueprints/zero_export_controller.yaml
input:
target_sensor:
name: Target power sensor (W)
description: What the inverter should deliver right now. Unavailable for 5 min turns the inverter off; below 40 W turns it off.
selector:
entity:
domain: sensor
grid_sensor:
name: Grid power sensor (W, + import / - export)
selector:
entity:
domain: sensor
grid_median_sensor:
name: Grid power median (3 readings)
description: A filter-platform median of the grid sensor.
selector:
entity:
domain: sensor
inverter_power:
name: Inverter AC power sensor
selector:
entity:
domain: sensor
inverter_limit:
name: Inverter non-persistent absolute limit
selector:
entity:
domain: number
inverter_producing:
name: Inverter producing
selector:
entity:
domain: binary_sensor
inverter_on:
name: Inverter turn-on button
selector:
entity:
domain: button
inverter_off:
name: Inverter turn-off button
selector:
entity:
domain: button
correction:
name: Limit correction (input_number, ~1.0)
selector:
entity:
domain: input_number
peak_power:
name: Max power (input_number, W)
description: Hard ceiling. Size it to your DC fuse/breaker/wire (80 % rule).
selector:
entity:
domain: input_number
raise_pending:
name: Raise-pending flag (input_boolean)
selector:
entity:
domain: input_boolean
mode: single
max_exceeded: silent
variables:
t_ent: !input target_sensor
g_ent: !input grid_sensor
gm_ent: !input grid_median_sensor
p_ent: !input inverter_power
l_ent: !input inverter_limit
prod_ent: !input inverter_producing
on_ent: !input inverter_on
off_ent: !input inverter_off
corr_ent: !input correction
pmax_ent: !input peak_power
rp_ent: !input raise_pending
triggers:
- trigger: time_pattern
seconds: "/20"
- trigger: state
entity_id: !input target_sensor
- trigger: state
entity_id: !input grid_sensor
actions:
- condition: template
value_template: >
{% set A = states[p_ent] %}
{{ not (A is not none and A.state in ['unknown','unavailable'] and (now() - A.last_changed).total_seconds() < 600) }}
- variables:
tstate: "{{ states(t_ent) }}"
target: "{{ states(t_ent) | float(0) }}"
corr: "{{ states(corr_ent) | float(1.0) }}"
pmax: "{{ states(pmax_ent) | float(1000) }}"
cmd: "{{ (([[target * corr, 30] | max, pmax] | min) | round(0) | int) }}"
cur: "{{ states(l_ent) | float(0) | round(0) | int }}"
since: "{{ (now() - states[l_ent].last_changed).total_seconds() }}"
stale_for: "{{ (now() - states[t_ent].last_changed).total_seconds() }}"
producing: "{{ is_state(prod_ent, 'on') }}"
off_age: "{{ (now() - (states(off_ent) | as_datetime(none) or (now() - timedelta(hours=1)))).total_seconds() }}"
on_age: "{{ (now() - (states(on_ent) | as_datetime(none) or (now() - timedelta(hours=1)))).total_seconds() }}"
exporting: "{{ states(gm_ent) | float(0) < 0 or states(g_ent) | float(0) < 0 }}"
settled: >
{% set L = states[l_ent] %}{% set G = states[g_ent] %}
{% if L is none or G is none %}true{% else %}
{{ (now() - L.last_changed).total_seconds() >= 12 and (G.last_reported - L.last_changed).total_seconds() > 11 }}{% endif %}
hard_export: >
{% set L = states[l_ent] %}{% set G = states[g_ent] %}
{{ G is not none and (G.state | float(0)) < -150 and (L is none or (G.last_reported - L.last_changed).total_seconds() > 4) }}
- variables:
cmd: "{{ [cmd, cur + 400] | min if cmd > cur else cmd }}"
- variables:
want_up: "{{ (cmd - cur) >= ([15, 0.04 * cmd] | max) }}"
- if: "{{ want_up and is_state(rp_ent, 'off') }}"
then:
- action: input_boolean.turn_on
target:
entity_id: "{{ rp_ent }}"
else:
- if: "{{ not want_up and is_state(rp_ent, 'on') }}"
then:
- action: input_boolean.turn_off
target:
entity_id: "{{ rp_ent }}"
- choose:
- conditions: "{{ tstate in ['unavailable','unknown'] }}"
sequence:
- if: "{{ stale_for > 300 and producing and off_age > 60 }}"
then:
- action: button.press
target:
entity_id: "{{ off_ent }}"
- conditions: "{{ target < 40 and settled }}"
sequence:
- if: "{{ producing and off_age > 60 }}"
then:
- action: button.press
target:
entity_id: "{{ off_ent }}"
default:
- if: "{{ not producing and on_age > 60 }}"
then:
- action: button.press
target:
entity_id: "{{ on_ent }}"
- if: >
{{ (cur - cmd >= [8, 0.03 * cmd] | max and (hard_export or (settled and (since >= 15 or exporting))))
or (cmd - cur >= [15, 0.04 * cmd] | max and settled and since >= 30
and is_state(rp_ent, 'on')
and (now() - states[rp_ent].last_changed).total_seconds() >= 20) }}
then:
- action: number.set_value
target:
entity_id: "{{ l_ent }}"
data:
value: "{{ cmd }}"
Feedback and improvements are welcome, here or as GitHub issues/PRs.