So this is intended to be more of a basic explanation to beginners to help them understand the Wh/mile metric specifically in regards to winter usage. It hopefully will show them that their usage is either normal, or give a reasonable explanation for their higher usage.
So your Wh/mile rating is high and you either want to know why, or you want to know if it is "normal". There are many reasons this can happen, and many ways to deal with it.
TL:DR(too long, didn't read). If you really want a TL:DR, here is my attempt but you really should read the rest, it's not that bad. Short trip and by extension multiple short trips are worse than long trips. This is because the energy use that goes into the Wh/mile(efficiency) value is better averaged over long trips. That's pretty much it, you'll have to read the rest to get more detail.
First things first. Where does the Wh/mile number come from. This accounts for all the energy used while in a driving mode(everything but PARK). In the winter when you have the heat on, and you are stopped at a light, all that heating energy will be added into your Wh/mile average and will decrease your efficiency(higher Wh/mile value).
So quick list of things that will cause lower efficiency(higher Wh/mile value):
Speed - The faster you go the more aerodynamic drag there is and even more power is required to overcome that drag force. In short, if you are going over 75-80 mph please don't complain about low efficiency.
Wind - This adds to, or subtracts from, your drag due to air resistance as discussed under Speed. For example if you are going 70mph and have a 10mph headwind, your car is going 80mph in terms of air resistance.
Rain/Snow - Rain and Snow increase rolling resistance. In these conditions you will have a measurable decrease in efficiency.
Outside temperature - I am only mentioning this to discount it technically. Outside temperature in and of itself doesn't really do anything. You can make some generalizations about temp vs air density but that is getting into the weeds for this discussion.
HVAC settings - So here is probably the biggest reason for increased power usage and decreased efficiency, especially in the winter time. The A/C during summer will have an effect as well but not near as much as your heat usage in the winter. When you get into a cold car, lets say 30F(cabin, outside temp...) and turn on your heat to whatever you decide, the heating element(or heat pump in newer cars) turns on to the max. Now the Heat pump(newer vehicles 2021) is drawing far less power than the heating element in the older cars(2017/18/19/20) and I don't have any numbers on the heat pump but this will still be a big draw at the beginning. So where you can help out is if you are able to have your car plugged in at home then before you leave for work or wherever, take out the App and turn on your climate. This will preheat the cabin and prevent that energy from being accounted for in your efficiency number.
The amount of energy required to maintain your desired cabin temperature is dependent on your desired temp, the Outside Temperature, as well as the heat loss caused by the outside conditions and how you are driving. Sitting still with no wind will have less effect than going 70mph down the road.
The other thing that can increase your cabin heat usage is not being on Auto and having the fan setting too low for the conditions. If for example you get into the car and turn on the heat but set the fan setting to a 1, then you will draw more power for a longer amount of time. This is because you may not be providing enough heating air flow to overcome the heat loses, and it will just take longer because of low air flow.
NOTE: I have a 2018 LR RWD which does NOT have a heat pump. If you have a Tesla with a heat pump, things work a bit differently and the efficiency hit for using the heat isn't as bad but it is still there and doesn't negate the concepts I am talking about.
So, those are some of the big reasons for decreased efficiency, but how can that relate to your specific driving patterns? Well there are two main driving conditions in my mind. Short trips and Long trips. The definitions of those are pretty wide and don't really matter too much but we can show some things with examples. I hit my character limit so please continue reading the first post below about Short Trips vs Long trips to finish this tutorial up.