Expect runtime to change with the workload
Steam Frame has a 21.6Wh battery. Locally running Beat Saber drained it in about an hour, while roughly two hours of streamed non-VR play ended with about half the battery remaining.

Watch the tested local-versus-streamed battery comparison.Playing this video connects to YouTube.
Charge correctly and extend the session
- What charger should I use?
- Use a Steam Deck charger or another USB-C charger rated at 45W or higher. No power supply is included, while Valve offers a 45W power supply for $29.
- How can I keep playing for longer?
- Route a cable from the rear USB-C port to an external battery. In testing, a 36Wh pack added an entire hour, while a 100Wh pack powered a 2.5-hour session and charged the headset.