Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Winter energy use for my Model S in Boston area

David29

Supporting Member
Aug 1, 2015
2,239
1,880
DEDHAM, MA
This winter, I tried to track my car’s energy use, to quantify just how much more energy the car uses in winter. We live in the Boston area, so it gets reasonably cold here, but not nearly as cold as in the upper Midwest or Canada.

I started tracking my energy use in November. Meteorologists seem to consider winter as being December, January and February. But we had a fairly mild February and March was quite cold, so my statistics are based upon the four months of December – March.

As background, I am retired, so I have no daily commute and consequently my mileage is relatively low in the winter. Also, I do a lot of short trips, so that tends to reduce efficiency and increase energy use. My car is parked outdoors, so I tend to use preheating a great deal.

Key results:

  • Over the four months, the car traveled 3230 miles and reported that it used 1234.9 kWh.

  • The average energy use per mile (as reported by the car) was 382.3 Wh/mile. The rate varied from 358.4 in March to 408.7 in January.

o This contrasts to my 2-year average of 323 Wh/mile.​

  • Average temperatures for the month varied from 29F in January to 38F in February.
  • Over the 4 months, I was billed for 1909 kWh by the utility, 55% more energy than the car reported using. (The car reports only the energy used from the battery, so energy used for preheating is not included while the car is plugged in.)
  • The excess energy reported by the utility was probably because of:

o Preheating the car – probably the main reason for the excess.

o Energy losses in the AC to DC conversion process, and some losses in the electrical system itself. (I have seen estimates that these losses could be as much as 10% of the energy used.)​

  • Using the local price for gas and the cost of the purchased electricity, the cost/mile for the power was equivalent to the cost of approximately 23.6 miles/gallon over the period, with variations of 20.1-26.7 mpg over the four months.

Although the total energy use (energy bought from the utility) is quite high, I was pleasantly surprised that the energy consumption reported by the car was not higher. Sometimes I see energy use displayed in the energy app in the 400-600 Wh/mile range, but that is for short periods. These data more accurately show what the car uses overall.

I was, however, startled by how much more energy I purchased than what the car reportedly used. I plan to track this through the warmer months as well, and hope to see a big drop in how much energy is used beyond what the car reports.

See the attachment for more detail.
 

Attachments

  • Summary_winter energy use Model S 70D.pdf
    129.1 KB · Views: 14
  • Like
Reactions: chjch

Warbird

Member
Oct 6, 2017
192
178
Boston
Nice! Might you post your spreadsheet? I'd like to see how the Excess formula works. Are you aware of the TexLab app that while more than tracking trips in detail, provides a breakdown of energy usage, including Phantom Drain (energy used while parked).
 

cmaster

Member
Dec 4, 2014
240
76
United States
This is what I had experienced in NH. I know many members in this forum think that driving a Tesla in subzero weather (this past January 2018 cold spout for several weeks) costs less than a gas car. I'm thinking to myself after hearing their defense, "Did they check their utility bill?"

For the month of January, I spent about 200$ in energy (cost of charging the car, preheating, etc...) vs $40 for my Honda Civic.
 
  • Informative
Reactions: David29

David29

Supporting Member
Aug 1, 2015
2,239
1,880
DEDHAM, MA
Nice! Might you post your spreadsheet? I'd like to see how the Excess formula works. Are you aware of the TexLab app that while more than tracking trips in detail, provides a breakdown of energy usage, including Phantom Drain (energy used while parked).
I did post the spreadsheet above. But the upload process did not "see" my xlsx files, so I assumed they were not allowed. Did I make a mistake?
And there really is no fancy math behind the calculation of what I called excess energy. I just subtracted the car's reported energy use for the month from what my utility meter said was used. I then calculated what percentage that was of what the car reported.
 

Warbird

Member
Oct 6, 2017
192
178
Boston
I did post the spreadsheet above. But the upload process did not "see" my xlsx files, so I assumed they were not allowed. Did I make a mistake?
And there really is no fancy math behind the calculation of what I called excess energy. I just subtracted the car's reported energy use for the month from what my utility meter said was used. I then calculated what percentage that was of what the car reported.

The forum probably fears XLSX file macros. You might try uploading it with .TXT extension.

How did you calculate:
- "Cost/Mile of Purchased Power"
- "Approx.Equivalent in MPG Regular"
 

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top