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Energy Usage in the cold, with ski racks, with a cargo box

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I've had my MS85 for a year and a half now (Oct 2014) and I know that when driving in the cold I get less mileage per charge. I am also confident that I will have reduced range with ski racks and/or a cargo box on top of my MS. Last week I drove from Boston's North Shore to Killington and I put the ski's and ski racks inside for the long drive then put them on the car once I arrived so I wouldn't be pulling the skis in and out of my car potentially scratching something. Then Friday we drove to Pinkham Notch, hiked to the shelters just below Tuckerman's Ravine, spent the night (w/ son's scout troop) then sledded down the next day. When we got back to the cars I threw backpacks, boot, crampons & snowshoes into the back & fronk of my MS, and it was packed full; plus two adults and three kids.

My point is I'm using my MS as a cargo van instead of using my racks (+rack accessories) due to my fear of reduced range. However, I really don't know actually how much the cold and racks reduce my range. So I am gathering data to figure this out.

I live in Swampscott, MA and work in Salem, NH. I drive up 129 to get onto 95/128S then take 93N to exit 2 in NH. For my experiment once I have merged onto 93N and set my cruise control (pre adaptive CC by 2 weeks grrrr) on 70mph I reset my trip log. As soon as I take the NH exit 2 20 miles later I look down and take note of my Wh/mile for this leg of my commute. When I get to my office 2 minutes later I look at the outside temperature and I log both the temp and Wh/mile in excel. At 70mph I should be able to keep a steady speed moving between the different lanes. Occasionally I'll have to slow down but so far I've spent less than 1 minutes of this 20 minute leg below 70mph. Also by the time I get onto 93N the battery and cabin should be at a steady temperature. My seat heater will be on 2 and the temperature will be set at whatever keeps me comfortable.

Once I have a good baseline I'll put my rack (Yakima Wispbar) on, then later my ski rack, then later my Thule car box.

I'm keeping track here https://www.dropbox.com/s/xbd2z4ip3cyrrc0/Energy Usage.xlsx?dl=0

I would be interested in any suggestions to improve my experiment.

- - - Updated - - -

I was quite disappointed in todays results, as you can see it was 6 degrees cooler when I arrived at work yet I only logged 350 Wh/m as opposed to 365 when it was warmer yesterday. Clearly I missed something. Yesterday I arrived at the office at 7:00 am, today I arrived at 8:30am but I can't see that this time difference would affect the usage.

Thoughts?
 
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Don't forget headwind/tailwind. Of course this is non-trivial given the weather and the curving roads.

Drag is the #1 highway consumption item, so any additional drag will be significant.

Unless you plan on taking 5 people, it would be much simpler to just use 60/40 folding seats to carry your equipment. Tesla needs to double the supercharger density around here to make ski trips easy and carefree, even without adding additional drag.