The Nest app can set the cooling temperature from a Flow, but there is no way to read it or to notice that it changed. A Flow can push a value into the thermostat and never get it back.
Cards today:
- When — Target temperature changed · Temperature changes · Humidity changed
- And — Thermostat mode is … · Eco-mode is enabled
- Then — Set temperature · Set cool temperature · Set thermostat mode · Eco-mode on/off
So target_temperature.cool has an action but no trigger and no condition. The thermostat mode has a condition but no trigger. The HVAC state has neither.
The values are already on the device — nothing extra has to be fetched from Google. This is a HomeyScript dump of a thermostat paired through the official app:
target_temperature = 22 (Heating temperature)
measure_temperature = 25.3 (Temperature)
nest_thermostat_mode = cool (Thermostat mode)
target_temperature.cool = 25 (Cooling temperature) ← no Flow card
nest_thermostat_hvac = cooling (HVAC) ← no Flow card
HomeyScript can read it, but a script has to be polled from a timer, so it can never be a WHEN card — a Flow reacts to a setpoint change late, or not at all.
Why it matters: in cooling season the cooling setpoint is the setpoint, and the heating one is inert. Mirroring the setpoint onto other climate devices, nudging fans or blinds when someone turns the temperature down, logging or notifying on changes — none of it has anything to attach to for half the year.
What I’d like:
- When — cooling setpoint changed · thermostat mode changed · HVAC state changed (each with the new and previous value as tokens)
- And — cooling setpoint is above/below … · HVAC state is …
- optionally a Then Read the cooling setpoint returning a token, for Advanced Flow
One detail worth flagging for whoever implements it: a thermostat in heating mode reports target_temperature.cool = null and flips back to a number when the mode changes. That should read as unknown rather than falling back to the last number — don’t fire the trigger when it becomes null, and let the comparison be false while it is unknown. A cooling setpoint is known condition makes that guard explicit.
I hit this myself and built a small read-only app as a workaround — it subscribes to a thermostat paired through the official Nest app and mirrors the values onto its own device so they gain Flow cards: GitHub - moKorean/com.lomohome.nest: Mirror a thermostat's cooling setpoint (target_temperature.cool) into Homey Flow · GitHub
It works, but it is the wrong shape: an extra device per thermostat, for values that are one card away from being usable already. It is MIT-licensed, so the capability mapping, the null handling and the card definitions are there for the taking if any of it is useful.