The way back can feel longer because it has less discovery to spend.

Time is measured by how much is new. The outward journey is full of things you have never seen, so attention has plenty to do and the distance passes quickly; on the way back the same road offers nothing to work on, and every kilometre is felt. Nothing about the route changed. What changed is the amount of noticing available.

You can put some of it back deliberately. Take a different road home, or look for one specific thing you missed on the way out, or travel back at a different hour. And when a stretch of life feels long and flat, the shortage may be novelty rather than energy.