The equation should count the fact, the temperature, the driver habit, the winter tire (If any), your need for heat or comfort in the cabin. Here's in Quebec we started new at 160km range and with -20c it's barely 105km (this is almost a 6 month old car) So we lost about 30% (btw i didn't change any driver habit since the EV came in my life).
I feel with what i've read in EV group, it's kind of normal. Li Ion have that particular reaction to cold. What i believe that what speak more is the SOH State of Health of the battery, it would be good to do a check on the battery after a year old.