Many people owns Smart home devices, either Google Nest, Amazon Alexa, Apple or other brands. One of the important platforms (beside HomeKit) to help end users manage all the various IoT devices at one place would be Home Assistant. You’d wish setting up Nest devices in Home Assistant is pretty easy, but it’s not easy and not free.
In order to get access to Nest devices in your Home Assistant instance, you’ll need to follow this guide from Home Assistant: https://www.home-assistant.io/integrations/nest/. Google changes their mind pretty often, so these are most likely need some updates every couple months.
The current setup strongly suggest you to have a Home Assistant Cloud (Nabu Casa) subscription. It costs $65 USD but can save lots of hurdle and the support is pretty fast.
In short, you’ll need to have a Google Cloud Platform account, setup a project, enable some Smart Home APIs and also pay a $5 fee for “Smart Home API”. Then you’ll also need to configure your HA instance to connect to Google, or it’s no use. After all these, you might see existing Nest devices shown up in your HA instance.
My new Google Home devices aren’t showing up! What should I do?
Now, this is where I feel dumb… I’m continuously adding new Nest devices to my home, and I’ve come to the realization that the new devices won’t show in Home Assistant instance because … you might guessed it … you did not authorize Nest to expose those devices.
It turns out that since the program have sandbox and commercial applications, and Home Assistant basically guided you to apply for a sandbox version (without Google “authentication”). This means the access is LIMITED and you actually need to manually grant each new devices to the HA instance by going to https://nestservices.google.com/partnerconnections/ and click on the project, check all the checkmarks next to the items you wish to share to Home Assistant instance.
It’s obviously not ideal, but … unless Google and Home Assistant decide to partner up and help all users, you’ll need to live with it.