Is updating a heavy load

Oskar2023 wrote:

Is updating a 2015 MacBook Pro a heavy load?

If you are updating you should always be on power adapter.

Yes I would consider an upgrade heavy load— there is a lot happening having to open, unpack, copy and insert and replace existing code, and verify the entire process was complete as expected.

You should not update your Mac unless it is plugged into power. You should never let your battery drain to 0% and doing so while updating may leave your computer unable to boot.