Is conserving energy something to do on a day-to-day basis, or over the week?
All other things being equal and provided the commute is no more than an hour you should be able to recover in full for the next day. 

I reckon that with decent food and rest you will always recover in time.

That said if the week is long and tiring and you don't get enough rest you may be slower on the Friday than on the Monday.