hubitat-heat-only-thermostat

name	hubitat-heat-only-thermostat
description	Capability profile and architecture patterns for heat-only thermostat drivers (electric floor heating, baseboard heat) on Hubitat.
domain	groovy
confidence	high
source	earned

Context

This skill applies when writing a Hubitat driver for a heat-only thermostat device — one that heats but does not cool and has no fan. Examples: SunStat/SunTouch electric floor heating, Stelpro baseboard heaters.

Capability Profile Decision

Declare Thermostat (combo) — not individual thermostat capabilities.

The Thermostat capability is required for:

• The Hubitat dashboard thermostat tile (setpoint +/− controls)
• Google Home / Alexa thermostat discovery
• Rule Machine thermostat-specific triggers

Individual capabilities (ThermostatHeatingSetpoint, ThermostatMode, etc.) alone produce a generic device tile and miss voice/RM integration.

Constrain the combo surface with attribute initialization:

sendEvent(name: "supportedThermostatModes",    value: JsonOutput.toJson(["heat", "off"]))
sendEvent(name: "supportedThermostatFanModes", value: JsonOutput.toJson(["auto"]))

Set these in installed(). Hubitat's dashboard and voice integrations respect these lists and hide unavailable modes.

Standard Capability Set (heat-only)

Capability	Include?	Notes
Actuator	✅	Required base
Sensor	✅	Required base
Thermostat	✅	Full combo for dashboard/RM/voice
TemperatureMeasurement	✅	Ambient temperature attribute
Refresh	✅	Manual state poll
Initialize	✅	Re-register polling on hub restart
ThermostatCoolingSetpoint	❌	Heat-only — skip
ThermostatFanMode	❌	No fan — skip
ThermostatSchedule	❌	Hubitat's shape is undefined; leave to Rule Machine

Thermostat Mode Guidance

Minimum mode set for a heat-only device:

["heat", "off"]

• Add "auto" only if the device exposes a schedule-following mode through the API as a distinct state.
• Do not use "emergency heat" for timed boost/override — use a custom setBoost(minutes) command instead. "emergency heat" carries HVAC-system semantics that confuse voice assistants on single-zone electric devices.

ThermostatOperatingState Values

For a heat-only device: "heating" and "idle" only. Never emit "cooling", "fan only", "pending heat", or "pending cool".

Custom Attributes for Dual-Sensor Devices

Many electric floor thermostats have both an ambient sensor and a floor probe sensor. Use:

attribute "floorTemperature", "number"   // floor probe
// "temperature" (from TemperatureMeasurement) → ambient

Temperature Unit Handling

Always emit temperature events with the hub's configured unit:

sendEvent(name: "temperature", value: convertedTemp, unit: location.temperatureScale)

Convert API values (typically Celsius) to Fahrenheit if location.temperatureScale == "F".

Examples

• drivers/sunstat-thermostat/sunstat-thermostat-child.groovy (planned v0.1.0 scaffold)

Anti-Patterns

• Declaring ThermostatCoolingSetpoint or ThermostatFanMode on a heat-only device.
• Using "emergency heat" mode instead of a custom boost command.
• Omitting supportedThermostatModes initialization — leaves the dashboard showing all mode options.
• Emitting temperature without specifying unit: — Hubitat may display wrong unit in dashboard.