lizprius2006 — The colder weather has a very considerable effect on fuel consumption. This applies, of course, to all internal combustion gasoline engine vehicles, not just hybrids. I don't know whether this is what's causing your current bad fuel economy (FE) numbers, but before you conclude that there's something wrong with your Prius, I suggest that you conduct an experiment. Take a decent return trip of say at least 50 miles each way. Have the vehicle warmed up before you start. Look at your trip's FE figure. If it's closer to what you were getting before (it won't be quite as good because of the colder air temperatures), I'd conclude that there's nothing wrong. If not, perhaps you do indeed have a problem.

Stan