Battery life varies by use and configuration. The Apple TV app movie playback test measures battery life by playing back HD 1080p content with display brightness set to 8 clicks from bottom.
Testing conducted by Apple in October 2020 using preproduction 13-inch MacBook Pro systems with Apple M1 chip, 8GB of RAM, and 512GB SSD.1TB = 1 trillion bytes actual formatted capacity less. Intel-based models are available with up to 32GB memory and up to 4TB storage.