This week, Nintendo released a fairly substantial update for the Switch 2, with one of the major new features being Handheld Mode Boost. Thanks to this, you can now play games from the original Switch on the Switch 2 in handheld mode with the same resolution and performance as if you were playing in docked mode.
This is obviously great news, but cranking up the performance naturally takes a toll on the battery. A Reddit user has now investigated this and played the 2019 version of Doom on the Switch 2 with Handheld Mode Boost, reporting that it caused the battery life to "go from 5 hours and 5 minutes to 3 hours and 43 minutes." In other words, a fairly significant reduction in battery life.
This is still welcome news but it might be a good idea to skip using the feature if you won't be able to charge for several hours or don't have a power bank.