ev surplus charging automation

EV Surplus Charging Automation

This guide explains how to wire your physical EV charger to follow HSEM's surplus-charging recommendations. HSEM calculates how much power the EV should draw (ev_charger_calculated_power), but the charger itself needs a different signal — it needs to know the grid surplus so it can dynamically adjust.

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Table of contents

1. Concept
2. The formula
3. go-e Charger (MQTT)
4. Easee Charger
5. Zaptec Charger

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Concept

HSEM recalculates ev_charger_calculated_power every 5 minutes (the planner's update interval). It tells you the target AC power the EV should draw right now — e.g. 2900 means "charge at 2.9 kW."

There are two ways to control a dynamic charger with this value:

Option A — HSEM directly controls the charge rate: Feed ev_charger_calculated_power into the charger. The charger draws exactly that amount. Simple, but if a cloud passes between HSEM updates the charger keeps drawing the old target — importing from the grid for up to 5 minutes.

Option B — Charger chases real surplus, HSEM sets a ceiling: Feed your real grid power sensor into the charger's surplus input so it responds to clouds instantly. Use HSEM's value as a maximum current limit so the charger never exceeds what the MILP planned. Requires two automations (or one script) per charger.

Both options are documented below. Choose Option B if your goal is "never import from grid for the EV."

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The formula

For Option A (HSEM direct control), the charger needs to know the remaining surplus after accounting for what it's already drawing:

pGrid = (ev_charger_calculated_power × -1) + current_charge_power

Variable	Source	Example
ev_charger_calculated_power	state_attr('sensor.hsem_workingmode_sensor', 'hourly_recommendation').ev_charger_calculated_power	2900 W
current_charge_power	Your charger's power sensor (W)	2000 W
pGrid	Sent to charger	-900 W

Worked example:

• HSEM says charge at 2900 W → target = 2900
• Charger is currently drawing 2000 W → charge = 2000
• pGrid = -2900 + 2000 = -900

The charger sees 900 W of remaining surplus and increases its draw. When it reaches 2900 W, pGrid = -2900 + 2900 = 0, and the charger holds steady — grid is balanced.

When HSEM says 0 W (no surplus), pGrid = 0 + 2000 = +2000, signaling the charger that it's importing from the grid and should back off.

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go-e Charger (MQTT)

go-e chargers accept pGrid, pAkku, and pPv via MQTT on the go-eCharger/<serial>/ids/set topic. The ids value decays after 10–15 seconds, so it must be refreshed continuously — the charger's PID loop then adjusts the actual charge power to drive pGrid toward zero.

Why pGrid instead of setting amps? The ids topic uses RAM-only registers designed for frequent writes. Setting the charge current directly via config keys like amp/ama writes to persistent storage (flash) on every update. See the go-eCharger MQTT docs for details.

Prerequisites

Entity	Purpose
sensor.hsem_workingmode_sensor	HSEM hourly recommendation with ev_charger_calculated_power
binary_sensor.go_echarger_<serial>_car	on when car is plugged in
sensor.go_echarger_<serial>_nrg_12	Current charging power in watts

Option A: HSEM direct control

Single automation — HSEM's ev_charger_calculated_power directly drives the charge rate. The go-e charger sees remaining surplus and ramps up/down to match the target.

alias: go-e Surplus Charging from HSEM
description: >-
  Sends grid surplus to go-e charger so it dynamically follows HSEM's
  EV charging recommendation.
triggers:
  - trigger: time_pattern
    seconds: /3
conditions:
  - condition: state
    entity_id: binary_sensor.go_echarger_222819_car
    state: "on"
actions:
  - data:
      qos: "0"
      topic: go-eCharger/222819/ids/set
      retain: false
      payload: |-
        {% set rec = state_attr('sensor.hsem_workingmode_sensor', 'hourly_recommendation') %}
        {% set target = rec.ev_charger_calculated_power | int(0) if rec is not none else 0 %}
        {% set charge = states('sensor.go_echarger_222819_nrg_12') | int(0) %}
        {
          "pGrid": "{{ (target * -1 + charge) }}",
          "pAkku": "0",
          "pPv": "0"
        }
    action: mqtt.publish
mode: single

Option B: Real surplus with HSEM ceiling

Two automations working together:

1. Surplus signal (every 3s) — feeds real grid power into pGrid so the charger's PID loop chases actual surplus second-by-second.
2. HSEM ceiling (on state change) — sets number.go_echarger_<serial>_pgt (grid target in watts) to HSEM's ev_charger_calculated_power. The charger will never exceed this, but will draw less when real surplus is low.

Automation B1 — Real-time surplus signal:

alias: go-e Surplus Signal from Grid Power
description: >-
  Feeds real grid power into go-e charger's pGrid so it dynamically
  follows actual solar surplus second-by-second.
triggers:
  - trigger: time_pattern
    seconds: /3
conditions:
  - condition: state
    entity_id: binary_sensor.go_echarger_222819_car
    state: "on"
actions:
  - data:
      qos: "0"
      topic: go-eCharger/222819/ids/set
      retain: false
      payload: |-
        {
          "pGrid": "{{ states('sensor.power_meter_active_power') | int(0) }}",
          "pAkku": "0",
          "pPv": "0"
        }
    action: mqtt.publish
mode: single

Automation B2 — HSEM ceiling:

alias: go-e Surplus Charging from HSEM
description: >-
  Simple automation to update values needed for using solar surplus with go-e
  Chargers
triggers:
  - trigger: time_pattern
    seconds: /3
conditions:
  - condition: state
    entity_id: binary_sensor.go_echarger_222819_car
    state: "on"
actions:
  - data:
      qos: "0"
      topic: go-eCharger/222819/ids/set
      retain: false
      payload: |-
        {
          "pGrid": "{{ (state_attr('sensor.hsem_workingmode_sensor', 'hourly_recommendation').ev_charger_calculated_power | int(0) * -1 + states('sensor.go_echarger_222819_nrg_12') | int(0)) }}",
          "pAkku": "0",
          "pPv": "0"
        }
    action: mqtt.publish
mode: single

Notes:

• Replace 222819 with your charger's serial number.
• Replace sensor.power_meter_active_power with your actual grid power sensor (negative = export, positive = import).
• pgt expects a negative value for surplus (export), so HSEM's positive watt target is negated (target * -1).
• The pAkku and pPv fields are set to 0 because HSEM manages the home battery separately — the charger only needs the grid surplus signal.

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Easee Charger

Easee chargers are controlled via the Easee EV Charger integration. The integration exposes a easee.set_charger_dynamic_limit service that sets the maximum charging current in amps.

Unlike go-e, Easee does not use a grid-surplus signal. Instead, you convert HSEM's power target directly to amps and set it as the charger's dynamic limit.

How it works

1. Convert HSEM's ev_charger_calculated_power (watts) to amps
2. Call easee.set_charger_dynamic_limit with the amp value
3. Use time_to_live so the limit expires if HA stops updating

Amps formula:

amps = ev_charger_calculated_power / (voltage × phases)

For a typical European 3-phase setup: amps = power_w / (230 × 3) ≈ power_w / 690. For single-phase: amps = power_w / 230.

Prerequisites

Entity	Purpose
sensor.hsem_workingmode_sensor	HSEM hourly recommendation with ev_charger_calculated_power
binary_sensor.easee_<id>_cable_connected	on when car is plugged in
sensor.easee_<id>_power	Current charging power in watts (for diagnostics)

Note: You also need an Easee Equalizer (HAN/Nevion) installed for dynamic current limiting to work. Without it, the charger ignores dynamic current commands.

Automation

alias: Easee Surplus Charging from HSEM
description: >-
  Sets Easee charger dynamic current limit based on HSEM's
  EV charging recommendation.
triggers:
  - trigger: state
    entity_id:
      - sensor.hsem_workingmode_sensor
conditions:
  - condition: state
    entity_id: binary_sensor.easee_12345_cable_connected
    state: "on"
actions:
  - action: easee.set_charger_dynamic_limit
    data:
      charger_id: "12345"
      current: >-
        {% set rec = state_attr('sensor.hsem_workingmode_sensor', 'hourly_recommendation') %}
        {% set target = rec.ev_charger_calculated_power | int(0) if rec is not none else 0 %}
        {% set amps = (target / 690) | round(0, 'floor') | int %}
        {{ ([0, amps, 32] | sort)[1] }}
      time_to_live: 30
mode: single

Notes:

• Replace 12345 with your charger ID (find it in the Easee integration device list).
• Replace 690 with 230 if you have a single-phase installation.
• The ([0, amps, 32] | sort)[1] pattern clamps between 0 and 32 A (Easee's range is 0–40 A; adjust the upper bound to match your circuit breaker).
• time_to_live: 30 means the limit expires after 30 seconds if HA stops sending updates — a safety net that prevents the charger from getting stuck at a high limit.

Alternative: circuit-level control

If you have multiple chargers on one circuit, use easee.set_circuit_dynamic_limit instead:

actions:
  - action: easee.set_circuit_dynamic_limit
    data:
      circuit_id: 12345
      current_p1: >-
        {% set amps = (states('...') | int(0) / 690) | round(0, 'floor') | int %}
        {{ ([0, amps, 32] | sort)[1] }}
      current_p2: "{{ ([0, amps, 32] | sort)[1] }}"
      current_p3: "{{ ([0, amps, 32] | sort)[1] }}"
      time_to_live: 30

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Zaptec Charger

Zaptec chargers are controlled via the Zaptec integration. The integration exposes a number.<name>_available_current entity on the Installation device that sets the maximum charging current in amps.

Like Easee, Zaptec does not use a grid-surplus signal. You convert HSEM's power target to amps and set it as the available current.

Important: Zaptec recommends not changing the available current more often than every 15 minutes. The automation below triggers on HSEM state changes only.

Prerequisites

Entity	Purpose
sensor.hsem_workingmode_sensor	HSEM hourly recommendation with ev_charger_calculated_power
binary_sensor.zaptec_<name>_connected	on when car is plugged in
number.<installation_name>_available_current	Sets max current for the installation

Before you start: Disable Zaptec Sense (APM/Automatic Power Management) and stand-alone mode in the Zaptec Portal. The charger must be in cloud-managed mode for the current limit to take effect.

Automation

alias: Zaptec Surplus Charging from HSEM
description: >-
  Sets Zaptec installation available current based on HSEM's
  EV charging recommendation.
triggers:
  - trigger: state
    entity_id:
      - sensor.hsem_workingmode_sensor
conditions:
  - condition: state
    entity_id: binary_sensor.zaptec_my_charger_connected
    state: "on"
actions:
  - action: number.set_value
    target:
      entity_id: number.my_installation_available_current
    data:
      value: >-
        {% set rec = state_attr('sensor.hsem_workingmode_sensor', 'hourly_recommendation') %}
        {% set target = rec.ev_charger_calculated_power | int(0) if rec is not none else 0 %}
        {% set amps = (target / 690) | round(0, 'floor') | int %}
        {{ ([6, amps, 32] | sort)[1] }}
mode: single

Notes:

• Replace my_charger and my_installation with your actual Zaptec entity names.
• Replace 690 with 230 if you have a single-phase installation.
• ([6, amps, 32] | sort)[1] clamps between 6 A (minimum most EVs accept) and 32 A (typical installation limit). Adjust to match your circuit breaker.
• If you have multiple chargers on one installation, changing the installation-level current affects all of them.

Alternative: per-charger control

If you need per-charger control (e.g. different cars on different schedules), use the zaptec.limit_current service instead:

actions:
  - action: zaptec.limit_current
    data:
      device_id: abc123def456
      available_current_phase1: >-
        {% set amps = (states('...') | int(0) / 690) | round(0, 'floor') | int %}
        {{ ([6, amps, 32] | sort)[1] }}
      available_current_phase2: "{{ ([6, amps, 32] | sort)[1] }}"
      available_current_phase3: "{{ ([6, amps, 32] | sort)[1] }}"

This sets the current on a specific charger rather than the whole installation. Find the device_id in the Zaptec charger device page.