In the EMS Web Portal, the thermostat serial numbers are available on the thermostat data files.
Steps to Finding the Serial Numbers
1. Log into your EMS Web Portal account at ecobee.com.
2. Open the Thermostat widget and select the thermostat for which the serial is needed.
NOTE: Users with multiple thermostats will need to select one thermostat at a time. The steps listed below will need to be repeated for each device.
3. Open the All Report widget and in the HVAC tab select "Download Data."
4. Select a date range (minimum three days up to three months) then select "Download." A CSV file will be saved to your computer.
5. Open the CSV file in excel, click on cell D1 and the serial number will show in full in the formula bar. Write down the serial number or copy/paste it into a separate file.