MQTT discovery: reactive_power device_class with VAR unit rejected by HA 2026.3

[Nosmoht]

Problem

Home Assistant 2026.3 rejects 6 MQTT discovery entities from smahub's HA-MQTT sink because of invalid device_class + unit_of_measurement combinations:

Entity	device_class	unit	HA Error
Reactive power consumption	reactive_power	VAR	VAR is not valid with reactive_power
Reactive power supply	reactive_power	VAR	same
Reactive power consumption counter	energy	kVAh	kVAh is not valid with energy
Reactive power supply counter	energy	kVAh	same
Apparent power consumption counter	energy	kVAh	same
Apparent power supply counter	energy	kVAh	same

The entities are never created in HA. All other SHM2 entities (active power, frequency, apparent power, phase angle) work correctly.

HA Error Log

ERROR [homeassistant.components.mqtt.entity] Error 'The unit of measurement `VAR` is not valid together with device class `reactive_power`' when processing MQTT discovery message topic: 'homeassistant/sensor/SMA-Sunny-Home-Manager-2/Reactive-power-consumption/config'

Root Cause

HA's sensor platform validates device_class against allowed unit_of_measurement values. As of HA 2026.3:

• reactive_power device class only accepts var (lowercase), not VAR
• energy device class does not accept kVAh (volt-ampere-hours are apparent energy, not active energy)

Suggested Fix

For reactive power sensors: Change unit_of_measurement from VAR to var (lowercase). HA expects SI-style lowercase for this unit.

For reactive/apparent energy counters: Either:

• Remove device_class: energy (these are not active energy) and use a generic sensor, or
• Use device_class: None with state_class: total_increasing to keep long-term statistics without device class validation

Environment

• smahub: v1.6.2 (container ghcr.io/anotherdaniel/smahub:v1.6.2)
• Home Assistant: 2026.3.4
• SMA device: Sunny Home Manager 2 (EM/SHM/SHM2, firmware 2.17.4.R)
• MQTT sink: HA_MQTT_ENABLED=true

[AnotherDaniel]

Thank you for taking the time to write this detailed report! I have done the VAR->var change, the latest release should not cause this error any more.

I could not find any entities that have the kVAh - energy-class combination, please let me know it that is a thing still.,