I own a Prius (not a PHEV though, just a hybrid) and can corroborate that my mileage goes down significantly in the winter months. It is a combination of a couple factors in my experience.
Needing to run the engine more to heat things up for defrosting and heating the cabin.
Related to the above, I tend to idle a lot more in the winter while cleaning ice/snow off the car, letting it warm up, or clearing the driveway.
Switching to winter tires (Blizzaks) negatively impacts rolling resistance compared to the LRR tires (Ecopias) I use the rest of the year.
I tend to average ~45 mpg in the summer and ~37 mpg in the winter over the past two years.
I own a Prius (not a PHEV though, just a hybrid) and can corroborate that my mileage goes down significantly in the winter months. It is a combination of a couple factors in my experience.
I tend to average ~45 mpg in the summer and ~37 mpg in the winter over the past two years.