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Seasonal Variation in Efficiency 2013 SV in Seattle

Posted: Wed Mar 02, 2016 4:59 pm
by jjgilham
I've attached a plot of my miles per kWh for my 2013 SV. I drive about 1300 miles a month (40 mile round trip commute + errands). I meter my L2 EVSE and I manually add infrastructure charging kWh on a monthly basis. The plot in blue is "from the wall" and the red plot is from Carwings (which also matches the car +- .1 mile/kWh, which I reset monthly). It represents a carefully collected data set.

Using carwings I get about 4.0 in the middle of winter and 5.1 in the summer and "from the wall" I get about 3.5 in winter and 4.5 in summer. There is a pretty strong correlation with the season. Efficiency has not varied much with age. I did notice an abrupt 3% or 4% loss in efficiency when I replaced the tires (OEM ecotopias to replacement ecotopias) but that did not really appear to persist beyond a month or two.

I have had not yet lost a bar and I have about 38K miles and 2.5 years on the car. The Pacific Northwest is a gentle climate for EVs. I find the efficiency differences surprisingly large given Seattle's benign climate. I use the AC and heat sparingly but I use the seat heater all winter. I do need to use defrost/defog functions frequently from Nov - March or when I have multiple people in the car.

I'm curious if others have similar data from other climates?


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Re: Seasonal Variation in Efficiency 2013 SV in Seattle

Posted: Wed Mar 02, 2016 5:18 pm
by Reddy
great set of data. The 20% difference (4-5 mi/kwh) is probably about right given the additional water on the roads in the winter. A couple of years ago there was a good summary of all EVs and the range loss in winter. Below 0 F the range was easily cut in half.

Re: Seasonal Variation in Efficiency 2013 SV in Seattle

Posted: Wed Mar 02, 2016 5:31 pm
by jjgilham
Are you suggesting that wet pavement is the principle factor?

I certainly don't approach "summer" efficiency on dry winter days. I always favored temperature as the larger factor, although I suspect it is a combination of a lot of different factors.

1) Temperature (cooler air is denser so wind resistance is larger)
2) Climate control (wipers, heater, defrost)
3) Wet pavement
4) Traffic patterns (generally better in summer )
5) Usage patterns ( I give my kids rides to school in the morning during the school season)