How long does a Nest thermostat take to charge?

When charging a Nest thermostat via USB, it typically takes 30 minutes (about half an hour) for your thermostat to recharge. However, if the battery is fully drained, then it can take up to two hours to recharge. When your thermostat is plugged in via USB, you will see a red flashing light at the top of the thermostat to confirm that your device is successfully charging.