Does a plug-in hybrid make sense if I cannot charge every day?

It can, but the benefit shrinks. A plug-in hybrid gets its best efficiency when you regularly drive on battery power; if you rarely charge, you are carrying a heavier battery and often get fuel economy similar to or lower than a regular hybrid. If you can charge most days for short commutes, a PHEV can cover much of your driving on electricity with gas backup for trips. Compare EPA ratings for both modes at fueleconomy.gov.