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EKM Digital Submeter Measures EV Charging Efficiency

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Electric vehicle owners may now know that 10-12% of drawn electricity is lost during the charging process when AC is converted to DC.

Energy usedThe “Since Last Charge” indicator on the Tesla Model S driver’s console keeps count of distance, energy used and average energy used per mile since the last time you unplugged, but matching this energy consumption to what you’re being billed by your company is more difficult than one might think.

Taking the 10.6kWh Total Energy readout from the dash and multiplying it by my billable electricity rate of $0.1670/kWh, I would think that it costs me $1.77 to drive 35.3 miles. However the actual costs are slightly higher because of the power conversion losses when charging. Charging via a standard 110V wall plug in the US is reported to be much less efficient than a NEMA 14-50 hence you’ll be using even more energy to reach the same state of charge.

Tesla’s charging calculator appears to take into account some of these charging loses. According to the calculator, 35 miles of range added to the Model S requires 11.6kWh of energy although I was able to achieve that with through 10.6 kWh as seen through my dash readout. This could imply a 91% charge efficiency but of course this is a very loose calculation and based on many assumptions such as the speed in which you drive, elevation changes and weather. It’s not simple to calculate how much actual energy you’re using to charge your Tesla Model S.

The EKM Digital Submeter

EKM Meter InstalledThe solution I found was to put a submeter between the EV charge outlet and main power supply. There are many types of meters on the market from basic kWh counters to advanced meters that can broadcast actual use over a wifi network, plot graphs, etc. After doing some extensive research, I decided to go with a metering solution from EKM Metering. My electrician did some independent research and came up with the same brand so I felt pretty good about my choice. I ended up purchasing the 100A kWh EKM digital submeter and enclosure.

My electrician was able to complete the installation in 3 hours with a portion of the time spent on retrofitting the EKM enclosure to accommodate for the larger 240v conduit. Total cost spent for products, labor and materials was $292.

How Does it Work?

The EKM submeter is like an odometer but with an energy readout that continuously increments as power is being drawn. There is no reset button. A blinking red light indicates that 1.25Wh is drawn per single blink of the LED.

Meter Reading

Measuring actual energy consumed over a specific time period requires taking some notes. Here are the the measurements and results of my tests:

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Model S Charging Efficiency

My results indicate that there’s approximately a 85% charging efficiency for my Tesla Model S which is less than the 91% efficiency that Tesla Motors seems to be using in their online calculator.

I’ll be performing several more tests over a longer period of time. I want to look at power draw differences while the Model S is asleep and also analyze variations in energy consumption due to software updates.

Conclusion

Overall the EKM Digital Submeter is a nice addition to any EV charging setup if you’re looking for a true picture of how much energy usage is going into your Tesla Model S / electrical vehicle. Assuming a $0.167/kWh electricity cost and 325 Wh/mile, the cost of the meter plus installation would require 5,380 miles of EV driving to break even.

If you’re looking for a cheaper alternative, simply add 15% to the energy usage readout on your EV to approximate the true energy cost per EV mile driven. Drive clean and drive smart!

 

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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

Lifestyle

Tesla brings perhaps the coolest interior feature to cars in latest update

Tesla adds on to the “fun” aspect of its vehicles.

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Credit: Tesla

Tesla has brought perhaps the coolest interior feature to its cars in a new update that is rolling out to vehicles now.

The feature will require a newer vehicle that has interior ambient lighting, which is present on the new Model S, Model X, Model 3 “Highland,” and Model Y “Juniper.” The Cybertruck also has ambient lighting strips throughout.

Tesla Model Y’s ambient lighting design changes revealed in leaked video

With the Version 2025.26+ Software Update, Tesla is rolling out a new “Sync Accent Lights w/ Music” feature, which is available on the Tesla Toybox:

To enable the feature, you’ll access the Toybox, choose “Light Sync,” and then choose “Sync Accent Lights w/ Music.”

Although it does not improve the performance of the vehicle, it is yet another example of Tesla making one of the coolest cars out there. This is truly a cool add-on that can be used to impress your friends and family.

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xAI, Musk Foundation helps schools near Memphis supercomputer site

Reports of xAI and the Musk Foundation’s work were recently posted by local news media.

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(Credit: xAI)

Elon Musk’s artificial intelligence startup xAI and the Musk Foundation have been supporting Memphis-Shelby County Schools with HVAC repairs and facility upgrades, while also funding youth programs for students in the area. 

Reports of xAI and the Musk Foundation’s work were recently posted by local news media.

xAI’s school visits lead to facility repairs

Representatives from xAI visited John P. Freeman Optional School, Fairley High School, and Westwood High School, all of which are located near its Colossus supercomputer site, to assess HVAC systems, plumbing, gym facilities, and athletic fields. The visits resulted in a list of priority repairs, some of which were completed in April and May.

In addition to the repairs, xAI also shared a number of initiatives that are planned for students in the area, as stated in a Commercial Appeal report.

“xAI is working on providing STEM workshops for local students, donating equipment to technical training programs, and supporting job fairs to boost employment opportunities. These initiatives reflect xAl’s commitment to fostering education and economic growth in Memphis,” xAI noted in a statement.

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Musk Foundation donation

Apart from xAI, the Musk Foundation also donated $350,000 to the Boys & Girls Clubs of Greater Memphis, enabling the reopening of two club sites located at Booker T. Washington High School and Westwood High School. Both locations had closed earlier this year due to lapses in funding. As per xAI, the Musk Foundation’s donation allows clubs to reopen for almost 1,000 students. 

The donation will fund staffing, supplies, and transportation, among others. “Kids are the future of humanity,” Elon Musk said in a statement, adding that students need “every chance to shoot for the stars.”

“We’re honored to support the Boys & Girls Clubs of Greater Memphis in reopening these sites, giving kids in underserved communities the tools to build brighter futures,” Musk said.

The gift was praised by local officials, including Boys & Girls Clubs board chair Michael Garriga, who stated that the “commitment will ensure the youth of our community have the opportunities they need to develop their skills and talents to become successful students and future citizens.”

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EV fans urge Tesla to acquire Unplugged Performance for edge in fleet and security industry

Unplugged Performance has built a name for itself by producing performance upgrades for Tesla vehicles.

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Credit: Unplugged Performance

A growing number of Tesla enthusiasts and longtime community voices are calling on the electric vehicle maker to acquire Unplugged Performance, a California-based aftermarket company best known for tuning Tesla vehicles and developing specialized government fleet solutions under its UP.FIT division.

The idea was once considered a niche proposal among EV fans, but it is now gaining serious attention not just as a performance play but as a strategic move to deepen Tesla’s roots in the fleet and security industry. 

A strategic fit

Unplugged Performance has built a name for itself by producing performance upgrades for Tesla vehicles, from track-optimized components to visual and aerodynamic upgrades. But in recent years, its UP.FIT division has pivoted toward a more functional future by outfitting Tesla vehicles like Model Ys for police, military, and government use.

That work has sparked growing calls for closer collaboration with Tesla, especially as the EV maker increasingly leans into autonomy, AI, and fleet services as core components of its next chapter.

“I posted this four years ago, but I think it’s more true now than ever,” wrote Whole Mars Catalog, a well-known Tesla investor and FSD Beta tester, on X. “Tesla should buy Unplugged. But not just as a Performance division. What they are doing with UP.FIT unlocks large government and commercial fleet purchases that can improve utilization.”

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Tesla fans such as shareholder Sawyer Merritt echoed the sentiment, calling Unplugged a “great fit within Tesla.” adding, “They are literally located directly next to Tesla’s design studio in Hawthorne.”

Enabling the next wave

Supporters of the idea noted that integrating Unplugged into Tesla’s corporate structure could help accelerate the adoption of autonomous technologies in government sectors. With UP.FIT patrol cars already in use across some U.S. police departments, Tesla fans envisioned a future where self-driving Teslas could potentially revolutionize law enforcement, search-and-rescue, and public service logistics.

“Just imagine how autonomous patrol cars could transform policing and bring us into a safer future,” the veteran FSD tester wrote.

The benefits could also extend to Tesla’s existing consumer base. “They also have some incredible products in the works that I think will appeal to many ordinary Tesla drivers — not just those looking for performance or mods. Stuff that’s so good it should have come straight from the design studio next door,” Whole Mars Catalog noted.

Unplugged Performance, founded in 2013, shares not just a product vision with Tesla, but also geography. Its Hawthorne headquarters sits directly adjacent to Tesla’s design studio, and the two companies have maintained a close working relationship over the years. The aftermarket firm has long positioned itself as a “mission-aligned” partner to Tesla.

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In response to the recent calls for acquisition, Unplugged Performance acknowledged the support from the community. “Our very existence is to support the Tesla mission with @UpfitTesla and @UnpluggedTesla,” Unplugged CEO Ben Schaffer posted on X. “We love working with Tesla and are grateful for the community’s support since 2013!”

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