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Charging a Tesla Model S Might Be Costing More Than You Think

Published

11 years ago

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Reported Energy UsedWhen you fill up a normal ICE car you know exactly what your costs are for the fuel. With an electric vehicle it is not that simple. There is a charging efficiency factor that comes into play which means that the reported amount of energy used could be understated and lower than the actual energy used. In a previous post I wrote about installing an EKM Digital Submeter on my NEMA 14-50 outlet to measure actual power usage of the Model S against the reported power displayed on the driver’s digital dash display. A month later and armed with more data, the energy loss I’m seeing is larger than I had originally expected.

Test Setup

I charge at home 99% of the time and in the last three months I’ve logged 7,500+ miles driven, one trip to the Supercharger and two visits to the Tesla store’s High Power Wall Connector. I have a professionally installed NEMA 14-50 outlet at home. I’m using the factory supplied Universal Mobile Connector (UMC) as the cable between the outlet and the car. An EKM digital sub meter measures actual draw from the outlet and is accurate to within 1% and does not add any measurable load of its own.

Methodology

On the “anniversary date” of taking delivery of my Model S I recorded all of the pertinent info that was displayed before resetting the Trip A meter. Before driving the next day I record the reading on the EKM meter. That way I’ve got the mileage and the Tesla reported power usage over the period driven. This process will let me see a bunch of information that I plan on tracking over time, as follows:

  • Monthly miles driven
  • Monthly kWh used as reported by the Model S
  • Monthly kWh used as reported by the EKM meter
  • Monthly Average energy used

I plan on using this information to look at how average energy used changes as the months/temperature changes and perhaps as the Model S gets more miles on it. While I don’t drive consistently on any given day (test drives, special trips and the like), the numbers will average out and my driving style is not likely to change much after 30 years of driving (yeah I’m getting old but the Model S makes me feel young again!). I also drive pretty consistent patterns of commuting with a lot of miles to the same places which helps average out the special trips to locations with different terrain/conditions. Basically, while the conditions aren’t perfectly stable over time, the averages and data from this real world testing will be pretty accurate.

The Data

The last period (6/21 – 7/21) was my first full period with both the car and the EKM meter. A month of driving and charging, especially with the miles and kWh’s involved is a decent period over which to look at the results versus the 2 days from my prior blog post. Here’s the data: Actual Energy June-Jul In the above table you can see that the Model S reported 728 kWh used during the period but the meter reported 894 kWh used. This means my charging efficiency is only about 82% and electric usage (and cost) is 23% higher than I may have expected based on the readings the Model S provides. For that month this is an extra $26 of charging cost which is a small number but a notable percentage of the total. The good news is that even using this larger kWh number, the savings versus driving my old ICE car for energy alone comes in at $334 — I’m saving $334/month in gas driving my Model S!

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"Rob's passion is technology and gadgets. An engineer by profession and an executive and founder at several high tech startups Rob has a unique view on technology and some strong opinions. When he's not writing about Tesla

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Lifestyle

Elon Musk seemingly confirms Cybertruck gift to 13-year-old cancer fighter

Diagnosed in 2018 with a rare form of brain and spine cancer with no cure, the teen has undergone 13 surgeries by the time he was 12.

Published

4 weeks ago

on

March 6, 2025

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Credit: Tesla

Elon Musk has seemingly confirmed that he will be sending a Tesla Cybertruck to 13-year-old Devarjaye “DJ” Daniel, a 13-year-old Houston boy fighting brain cancer. The teen was recognized as an honorary Secret Service member by U.S. President Donald Trump during his address to Congress on Tuesday. 

A Chance Meeting

The Tesla CEO’s Cybertruck pledge was mentioned during DJ’s short interview with CNN’s Kaitlan Collins. When Collins asked the 13-year-old what he told the Tesla CEO, DJ answered that he asked for a Cybertruck.

“I said, ‘can you do me a big favor, when you get back to Houston can you send us a Cybertruck down there?’” the cancer fighter stated.

Daniel noted that Musk responded positively to his request, which was highlighted by Collins in a post on X. Musk responded to the post with a heart emoji, suggesting that he really will be sending a Cybertruck to the 13-year-old cancer fighter.

Teen’s Cancer Battle Inspires

Diagnosed in 2018 with a rare form of brain and spine cancer with no cure, Daniel has undergone 13 surgeries by the time he was 12. During his speech, Trump highlighted the 13-year-old’s long battle with his disease. 

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“Joining us in the gallery tonight is a young man who truly loves our police. The doctors gave him five months at most to live. That was more than six years ago. Since that time, DJ and his dad have been on a quest to make his dream come true,” Trump stated.

Daniels officially received an honorary badge from U.S. Secret Service Director Sean Curran, to much applause during the event.

Surprisingly Partisan

While Daniels’ story has been inspiring, Trump’s focus on the 13-year-old cancer fighter has received its own fair share of criticism. MSNBC host Nicolle Wallace, while referencing Daniels’ love for law enforcement, noted that she is hoping the 13-year-old never has to defend the U.S. capitol against Trump supporters. “If he does, I hope he isn’t one of the six who loses his life to suicide,” Wallace stated.

Anti-Musk and Trump accounts on X have also thrown jokes at the cancer fighter’s honorary badge, with some dubbing the 13-year-old as a “DEI hire” that should be looked into by DOGE.

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Tesla owner highlights underrated benefit of FSD Supervised

Published

2 months ago

on

January 31, 2025

By

Credit: Tesla

Elon Musk has been pretty open about the idea of FSD being the difference maker for Tesla’s future.

If Tesla succeeds in achieving FSD, it could become the world’s most valuable company. If it doesn’t, then the company would not be able to reach its optimum potential.

FSD Supervised’s safety benefits:

  • But even if FSD is still not perfect today, FSD Supervised is already making a difference on the roads today.
  • This was highlighted in Tesla’s Q4 2024 Vehicle Safety Report.
  • As per Tesla, it recorded one crash for every 5.94 million miles driven in which drivers were using Autopilot technology.
  • For comparison, the most recent data available from the NHTSA and FHWA (from 2023) showed that there was one automobile crash every 702,000 miles in the United States. 

FSD user’s tale:

  • As per an FSD user’s post on social media platform X, FSD Supervised was able to help him drive a relative to a medical facility safely even if he was exhausted.
  • During the trip, the driver only had to monitor FSD Supervised’s performance to make sure the Tesla operated safely.
  • In a vehicle without FSD, such a trip with an exhausted driver would have been quite dangerous. 
  • “This morning, Tesla FSD proved to be an absolute godsend. I had to take my brother-in-law to the hospital in Sugar Land, TX, which is 40 miles away, at the ungodly hour of 4 AM. Both of us were exhausted, and he was understandably anxious about the surgery.
  • “The convenience of sending the hospital’s address directly from my iPhone to my Tesla while still inside my house, then just a single button press once inside, and 40 miles later we were precisely in front of the hospital’s admissions area.This experience really underscores just how transformative this technology can be for society,” Tesla owner JC Christopher noted in his post.

Don’t hesitate to contact us with news tips. Just send a message to simon@teslarati.com to give us a heads up.

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Lifestyle

Tesla Optimus “stars” in incredible fanmade action short film

Published

3 months ago

on

January 14, 2025

By

Credit: @SoKrispyMedia/YouTube

There are few things that prove an enthusiast’s love towards a company more than a dedicated short film. This was highlighted recently when YouTube’s SoKrispyMedia posted a 10-minute action movie starring Optimus, Tesla’s humanoid robot, as well as several of the company’s most iconic products. 

The video: 

  • Shot like a Hollywood action flick, the video featured a rather humorous plot involving a group of thieves that mistakenly targeted a Tesla Model 3 driver. 
  • The Model 3 driver then ended up speaking to Tesla for assistance, and some high-octane and high-speed hijinks ensued.
  • While the short film featured several Tesla products like the Model 3, Superchargers, and the Cybertruck, it is Optimus that truly stole the show.
  • Optimus served several roles in the short film, from an assistant in a Tesla office to a “robocop” enforcer that helped out the Model 3 driver.

Cool inside jokes: 

  • The best Tesla videos are those that show an in-depth knowledge of the company, and SoKrispyMedia definitely had it. 
  • From the opening scenes alone, the video immediately poked fun at TSLA traders, the large number of gray Tesla owners, and the fact that many still do not understand Superchargers.
  • The video even poked fun at Tesla’s software updates, as well as how some Tesla drivers use Autopilot or other features without reading the fine print in the company’s release notes.
  • The video ended with a tour de force of references to Elon Musk products, from the Tesla Cybertruck to the Boring Company Not-a-Flamethrower, which was released back in 2018.

Check out SoKrispyMedia’s Tesla action short film in the video below.

Don’t hesitate to contact us with news tips. Just send a message to simon@teslarati.com to give us a heads up.

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