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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.

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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:

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.

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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!

 

"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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Tesla hit by Iranian missile debris in Israel

A Tesla in Israel absorbed a direct hit from missile debris, and the glassroof held.

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Tesla Model Y glass roof shattered from a piece of falling Iranian missile debris

On March 30, 2026, Lara Shusterman was in Netanya, Israel when Iranian ballistic missiles triggered air raid sirens across the city. While she remained in safety, her 2024 Tesla Model Y did not escape untouched. A heavy piece of missile debris struck the car’s massive glass roof, leaving a deep crater but without shattering. In a Facebook post to the Tesla Israel community the following morning, Shusterman described what happened: “The glass did not shatter into dangerous shards. She stopped the damage and pushed the metal part to the ground.” She closed by thanking Elon Musk and the Tesla team for building what she called “security and a sense of trust even in extreme situations.”

Netanya is a coastal city in central Israel, roughly 18 miles north of Tel Aviv and has been among the areas most frequently struck during Iran’s ongoing missile campaign, following coordinated U.S. and Israeli strikes on Iranian military infrastructure. Falling shrapnel from intercepted missiles is a common occurrence.

Source: Tesla Israel Facebook Group

The incident is a testament to Tesla’s structural engineering. Tesla’s glass roof is designed to support over four times the vehicle’s own weight. That strength has shown up in real-world accidents too. In 2021, a Model Y in California was struck by a falling tree during a storm, with the glass roof holding firm and the cabin remaining intact. In another widely reported incident, a Tesla Model Y plunged 250 feet off the cliff at Devil’s Slide in California in January 2023, with all four occupants, including two young children, surviving.

Disturbing details about Tesla’s 250-foot cliff drop emerge amid initial investigation

Tesla officially launched sales in Israel in early 2021 and captured over 60 percent of Israel’s EV market in the first year. The brand’s foothold in Israel remains significant. Tens of thousands of Teslas are now on Israeli roads, making incidents like Shusterman’s easy to corroborate. On the same week her Model Y took the hit, the U.S. Space Force awarded SpaceX a $178.5 million contract to launch missile tracking satellites, a separate but fitting reminder of how intertwined the Musk ecosystem has become with the realities of modern conflict.

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NASA sends humans to the Moon for the first time since 1972 – Here’s what’s next

NASA’s Artemis II launched four astronauts toward the Moon on the first crewed lunar mission since 1972.

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NASA’s Space Launch System rocket launches carrying the Orion spacecraft with NASA astronauts Reid Wiseman, commander; Victor Glover, pilot; Christina Koch, mission specialist; and CSA (Canadian Space Agency) astronaut Jeremy Hansen, mission specialist on NASA’s Artemis II mission, Wednesday, April 1, 2026, from Operations and Support Building II at NASA’s Kennedy Space Center in Florida. NASA’s Artemis II mission will take Wiseman, Glover, Koch, and Hansen on a 10-day journey around the Moon and back aboard SLS rocket and Orion spacecraft launched at 6:35pm EDT from Launch Complex 39B. (NASA/Bill Ingalls)

NASA launched four astronauts toward the Moon on April 1, 2026, marking the first crewed lunar mission since Apollo 17 in December 1972. The Artemis II mission lifted off from Kennedy Space Center aboard the Space Launch System rocket at 6:35 p.m. EDT, sending commander Reid Wiseman, pilot Victor Glover, mission specialist Christina Koch, and Canadian astronaut Jeremy Hansen on a 10-day journey around the far side of the Moon and back.

The mission does not include a lunar landing. It is a test flight designed to validate the Orion spacecraft’s life support systems, navigation, and communications in deep space with a crew aboard for the first time. If the crew reaches the planned distance of 252,000 miles from Earth, they will set a new record for the farthest any human has ever traveled, surpassing even the Apollo 13 distance record.

Elon Musk pivots SpaceX plans to Moon base before Mars

As Teslarati reported, SpaceX holds a central role in what comes next. The Starship Human Landing System is under contract to carry astronauts to the lunar surface for Artemis IV, now targeting 2028, after NASA restructured its mission sequence due to delays in Starship’s orbital refueling demonstration. Before any Moon landing happens, SpaceX must prove it can transfer propellant between two Starships in orbit, something no rocket program has done at this scale.

The last time humans left Earth’s orbit was 53 years ago. Gene Cernan and Harrison Schmitt of Apollo 17 were the final people to walk on the Moon, a record that stands to this day. Elon Musk has long argued that returning is not optional. “It’s been now almost half a century since humans were last on the Moon,” Musk said. “That’s too long, we need to get back there and have a permanent base on the Moon.”

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The Artemis program involves 60 countries signed onto the Artemis Accords, and this mission sets several firsts beyond distance. Glover becomes the first person of color to travel beyond low Earth orbit, Koch the first woman, and Hansen the first non-American astronaut to reach the Moon’s vicinity. According to NASA’s live mission updates, the spacecraft’s solar arrays deployed successfully after liftoff and the crew completed a proximity operations demonstration within the first hours of flight.

Artemis II is step one. The Moon landing and the permanent lunar base come later. But after more than five decades, humans are heading back.

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Elon Musk

Tesla Optimus Gen 3 is coming to the Tesla Diner with new ambitions

Tesla’s Optimus robot left the Hollywood Diner within months of opening. Now Musk is planning its return with a bigger role and a major Gen 3 upgrade underway.

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Tesla Optimus Gen 3 [Credit: Tesla]

Tesla’s Optimus robot was one of the most talked-about features when the Tesla Diner opened on Santa Monica Boulevard in Hollywood on July 21, 2025. Dubbed “Poptimus” by Tesla fans, the Gen 2 robot stood upstairs at the retro-futuristic, drive-in theater and Tesla Supercharging station, scooping popcorn into bags and handing them to guests with a wave.

The diner itself had been years in the making. Elon Musk first floated the idea in 2018 with a tweet about building an “old-school drive-in, roller skates & rock restaurant” at a Hollywood Supercharger. What eventually opened was a unique two-story neon-lit space, with 80 EV charging stalls, and Optimus serving as a live demonstration of where Tesla’s ambitions were headed.


But Optimus did not stay long, and was gone by December 2025.

Now, the robot is set to return with a more demanding job. Musk has ambitions for Optimus to take on a food runner role in 2026, delivering meals directly to cars at the Supercharger stalls. While the latest Gen 3 Optimus is likely to initially take on its previous popcorn-serving role, it wouldn’t be out of the question for Optimus to see a quick promotion. With improved  hand dexterity that features 50 total actuators and 22 degrees of freedom per hand, and significantly more powerful processing through Tesla’s latest AI5 chip that includes Grok-powered voice interaction, Musk described Optimus at the Abundance Summit on March 12, 2026, as “by far the most advanced robot in the world, Nothing’s even close.”

That confidence is backed by a major manufacturing shift. At the Q4 2025 earnings call in January, Musk announced Tesla would discontinue the Model S and Model X and convert those Fremont production lines to build Optimus. “It’s time to basically bring the Model S and X programs to an end,” he said, calling for a pivot that reflects where the Tesla’s future lies.

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