2026.4.4
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WattTime

The WattTime integrationIntegrations connect and integrate Home Assistant with your devices, services, and more. [Learn more] allows users to get real-time emissions data for a latitude/longitude from WattTime.

Registering an account

You need a WattTime account before you can set up this integration. Registration is done via the WattTime API. The simplest way to register is by using cURL on the command line:

curl -X "POST" "https://api.watttime.org/register" \
     -H 'Content-Type: application/json' \
     -d '{
       "username": "<USERNAME>",
       "password": "<PASSWORD>",
       "email": "<EMAIL>",
       "org": "<ORG>"
     }'

The org value can be anything you like. It does not need to represent a real organization.

Configuration

To add the WattTime service to your Home Assistant instance, use this My button:

Manual configuration steps

If the above My button doesn’t work, you can also perform the following steps manually:

  • Browse to your Home Assistant instance.

  • Go to Settings > Devices & services.

  • In the bottom right corner, select the Add Integration button.

  • From the list, select WattTime.

  • Follow the instructions on screen to complete the setup.

Sensors

Note

The sensors available to you will depend on the type of WattTime subscription you have. You can reach out to WattTime to upgrade your subscription via their website.

Name Subscription Level Meaning
Marginal Operating Emissions Rate Pro The currently measured amount of lbs of CO2 per MWh
Relative Marginal Emissions Intensity All A percentage between the lowest (cleanest) and highest (highest) MOER values observed in the past two weeks

You can learn more about the data that WattTime collects in the WattTime API documentation and on the WattTime solutions page.