John Goreham's picture

Tesla owner's garage fire highlights EV charging safety and cost

A recent fire in a garage in which a Tesla was charging is a good reminder that EVs draw enormous current while charging. EV buyers should carefully plan their charger location and include the cost in their budget. Here are some things to consider if you plan to charge at home.

A fire in Irvine California this past month highlights the fact that electric cars use more electricity than any other household appliance. The outlet in your garage was not intended to provide high amperage over a long period of time to charge a car. Like all appliances that draw a lot of current, any outlet that is used to charge an EV should be specifically designed and installed to accommodate that service.

EV Home Charger Wiring Basics
When an air conditioner or other large appliance is added to a home electricians do not tap into the existing wiring circuit closest to that appliance. Rather, they create what they call a “home run.” A home run is a circuit that goes from the single point of use directly back to the home’s main electrical panel. There are no other outlets on that wire. In addition, the circuit breaker that is between the appliance and the electrical supply (which is located in the electrical panel) will be added specifically for the service it will provide and it will be dedicated to just that one line.

A Tesla Model S can come with a battery pack as large as 85 kWh. That is pronounced 85 kilo Watt hours. This unit is a measure of power x time (energy). Take a look at your electrical bill. Mine says that I used a total of 644 kWh in all of November. That means that if I charged a Tesla from empty to full about 8 times, which would be twice per week, I would literally double my total electrical usage in the home. Charging 8 times would result in a range of about 2,000 miles per month. That is a lot of miles, but well within the amount of miles many Tesla owners report driving on forums we participate in. The upshot is that adding a powerful EV like a Tesla can double the amount of power your home’s electrical system handles. We are not trying to play any games here. If you feel the math has a logical error please reply below and we will re-check it.

On its website Tesla says “Most outlets are either standard 110 volt outlets or higher powered 240 volt outlets. Higher powered outlets charge between four and six times faster than standard household outlets. If you plan to install an outlet in your garage, we recommend a NEMA 14-50 240 volt outlet.” That is the type of heavy duty connection that an RV might use. It should be noted that the current rating on that is 50 amps (40 amps continuous draw). In your home there is nothing else that draws that much power. In fact, most New England homes built before the 1980s had only 60 amp service to the entire house. Now 100 amp or 200 amp is the norm. If your house has only 60 amp service you may need to change the entire electrical box. I did that on my home when I added a generator and AC system to my house. I paid about $1500 at the time, 15 years ago.

So far we have discussed the electrical service needs (not 60 amp), electrical panel needs (dedicated circuit breaker), and the wiring (home run to the point of use) for an EV. Tesla can help buyers with the proper in-car charging system (it offers both single and double) and also the type of home connector to use. Tesla also has a special High Power Wall Connector it can provide to owners who need fast, frequent charges. In its section on charging Tesla starts out noting that a “normal” 110 volt wall socket can only add 3 miles per hour of range to a Tesla Model S. Some quick math gives us a required charging time to add 240 miles of 80 hours! Clearly, that is not going to work for people who own these cars. It is just a nice option to have in emergency situations, or when one wishes to simply top off the battery on the road at a hotel.

Plan On an Electrician and Building Permit
If it has not yet become absolutely clear to the reader these electrical upgrades are not a homeowner project. In fact, they are not a handyman-service project either. Adding an EV charging point to a home should only be done by a licensed electrician who has pulled a building permit from the local town or municipality. Here in Massachusetts where I live, that would also result in the electrical building inspector visiting the jobsite after work is complete, inspecting the job to ensure it meets the code requirements for the town, and then the electrical inspector would sign the building permit if all was to his or her satisfaction. Anything less than this and your home-owner’s insurance policy is not required to cover problems like a garage fire that result from work done that was not to code. Here is what Tesla says about preparing your garage for your new Tesla:

“We recommend working with a trusted electrician to install your High Power Wall Connector or NEMA 14-50 outlet before your Model S arrives. All Model S include a Mobile Connector cable and an adapter for the NEMA 14-50 outlet. Depending on your home’s electrical system, installing a high Power Wall Connector at maximum amperage may be more difficult that installing a 240 volt outlet due to power availability. The High Power Wall Connector can be set to any amperage level. While you won’t charge at the rate of 58 miles per hour of charge, you will be able to enjoy the convenience of a sleek, permanently installed Connector.”

Home EV Charging Point Cost
The total cost to install a proper EV charging point in a home can start at about $750 for a home-run circuit and appropriate low current rating wall connector. The Tesla High Power Wall Connector requires a 100 amp circuit breaker to get the fastest charge rating. Most houses in New England cannot accommodate that. Adding 200 or 400 amp service, wiring the home run circuit and buying and installing the High Power Wall Connector could cost as much as $6,000.00. Our estimate is based on Tesla Forum discussions that say the electrical work including an upgrade to 200 or 400 amp service can range to as high as $3,000 and the Tesla website which lists the High Power Wall Charger and second on-board charger as a $2,700 adder to the car’s price tag. It should be noted that $6,000 will buy a lot of gas. In fact, it will buy 1,714 gallons of gasoline at today’s price of less than $3.50 per gallon. A 25 MPG car can travel about 43,000 miles on that amount of money. Again, we stress that these are the two bookends of the range one might pay.

The fire in Irvine California seems to have occurred at the connection between the Tesla’s cable and the wall. Here is what one news report summarized the Tesla response as being; "“The cable was fine on the vehicle side; the damage was on the wall side,” Tesla said of the garage fire. “Our inspection of the car and the battery made clear that neither were the source.”" We reached out to the Orange County Fire Authority for a comment and we asked if the job was recorded by a signed building permit, or their equivalent code requirements. They did not reply.

Evs are a part of the automotive present, not future. Those shopping for a new EV, particularly a Tesla, should include the cost to install the charger and make an installation plan including an electrician and building permit.

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Typo: "recorded by a singed" -> "recorded by a signed" although I think it would be clearer saying something more like "we asked if the job was covered by a signed building permit and met existing code".
Thanks for the comments Stephen. I caught that typo shortly after publishing and it is fixed. More importantly, we see you are a "frequent flyer" now at Torque News and that makes us very happy! Thanks very much for reading and helping with the proof reading. Frankly, it is my biggest challenge and I will take all the help I can get. Cheers,
Let's not forget that a Tesla S is a $70k MSRP car. Sales taxes are likely more than the cost of upgrading your electrical installation. If you are buying this car to "save" money on gas, clearly you need to rethink your approach. This may be more meaningful for a full electric Ford Focus, which MSRP is half of that. Even there, the math is a stretch and you would need to drive a LOT to even out the initial investment cost.
Thanks David. I tend to agree with you. I'm a geek and I like to run numbers. For me the EV payoff is not as apparent. - - One trend I do notice is that a lot of EV owners compare their new EV to their very old ICE car. When they run those numbers the EVs look pretty good. However, a Leaf compared to a 2014 Prius? Or in the case of a Tesla - compared to a Lexus GS hybrid? I come to a different financial conclusion than some EV owners seem to. - - However, I do respect the EV owners for stepping up for other reasons. Also, I can totally get owning a Tesla just because it is an amazing car.
"Charging 8 times would result in a range of about 2,000 miles per month. That is a lot of miles, but well within the amount of miles many Tesla owners report driving on forums we participate in." -- This isn't fair. It's anecdotal at best. IIRC, the average American car drives about 1,000 miles per month. That SOME Tesla owners drive 2,000 mpm in no way suggests what the AVERAGE Tesla owner does. Of course, it is possible that those who drive a lot are attracted more to long-range electric vehicles like Model S. Although I do not expect to recapture the cost of that expensive car with fuel savings, some might. On a typical day, I drive less than 50 miles. How about you? I can load 50 miles of range into my Model S from my NEMA 14-50 circuit in about two hours, usually from 12:00 - 2:00 AM. I hope Tesla updates its software to let owners specify when they want their charge to END rather than when it should BEGIN as it works today. It's what we call SMOP here in Silicon Valley - a Simple Matter of Programming. My car downloads an update every few months, also while I sleep. Maybe my pet feature will be next?! Electricity costs vary wildly around the country, within a state and even around the clock. I have heard people quote costs as low as $0.07 per KWh. I was paying about $0.34 per KWh until I went on the EV rate. Now I charge my Tesla at night at about $0.10 per KWh. In one year, I have averaged 327 Wh per mile (11,000 miles, slightly below average) for a cost of about three cents per mile. I am pleased with this. Like you sort of say, there is no fire danger from a properly installed, high current charging circuit. Yes, older homes may require more expensive retrofits in order to become EV-friendly. My 50+ year-old home in CA already had a 200A panel. The quoted cost to run the 14-50 circuit was $600 but IIRC it ended up about twice that because there was no more room in the panel and the electrician had to install a small sub-panel on the wall next to the main panel. The inspector signed it off and all is well.
Thanks Rick. I needed to use some round numbers, but in fact we recently ran a story about a Leaf owner that drove 100,000 miles in one year. Under a different story we had a Tesla owner comment that he drives about the same. We also had a huge amount of commentary by EV owners saying that their Tesla is their primary, or only car and that they drive a lot. I drove about 23K this past year. My days alternate between local travel and about 130 miles to visit family a few times per week. - - The most important thing I appreciate about your comment is that it says "Inspector signed off." I was not sure that was required in CA. If I was the homeowner who had the fire I would be very angry and I would find out why my home was almost destroyed. A part failure alone should not have allowed a fire. ---Also, there is a recent story here at TN where EV owners did write in and they claim their EV cost them next to nothing and they did do it for the money. Also, I have read similar comments from Tesla owners on forums who say by their math the Tesla is very affordable. My math is not so rosy, but I respect their move for other reasons. - - Thanks again for taking time to write in.
Any tesla owner and in fact any potential owner will see through this absurdly bias story, and in fact install safe and inexpensive charging systems. This is not even a smart try at knocking EVs.
Thank you for your opinion Tony. Did I not mention that EV charging at home can start at $750 if one has a lot of time? If there is a cheaper setup detail it for us. You can find the cost adder for the wall charger on Tesla's webpage ($2,700). To get to the cost adder for a Tesla simply start the "Order" configurator. The charger mentioned in the story comes up as an adder just after you begin. Be sure you have selected "Cash" rather than finance. Or it will hide the cost of the adders and just show the lease price change. The wall mounted part alone is also sold separately by Tesla ($1200). Here is their webpage link: - Also, you can see the posts from which I took the numbers about home install costs on the Tesla official webpage blog. - You can also visit this website to read the fire report from OCFA. In the report you will see that the homeowner in fact did do the installation as I describe in the article. Here is that link: Electrical work is expensive. Poor electrical work can be even more costly.
Here is a cut and paste from the Tesla configurator. Sorry it loses its formatting: High Power Home Charging Outfit Model S with a second onboard charger and install the High Power Wall Connector in your garage. This combo lets owners charge quickly at home and ensures your Mobile Connector is always in the trunk for charging on the go. •Second onboard charger •High power wall connector Charge at up to 62 miles per hour (80 amps) $2,700
Your article sheds light on the fact that an electric car is not a cheaper mode of transportation, simply an alternative one. If we take a look at the math indicated here, we find that the Tesla will cost no less than .15 cents per mile to fuel, based on your 2000 mile per month average. I'm from Southern Cal, and the PG&E rates are not cheep. Bottom Line: I'm not so damned sure that the Tesla has a lesser impact on the environment than an ecologically sound 40 mpg internal combustion driven auto.. After-all, the power plants in Southern California are Fuel or coal fired. Please demonstrate otherwise...
Thanks Parks. It is nice to know I am not the only one that sees that. I had no idea that CA used any coal plants (or fuel plants). I will say that I love Teslas./ However, when the crazy lease scheme came out I ran the numbers using the Tesla calculator and when I put in my electric rate there was no way the savings offset the high cost of the Tesla. I think the Model S stands solidly in the value category. It is so darn good it is clearly a competitor to an Audi RS 7 or similar car. However, I can't make the math work the way some owners can. Compared to other green choices like a Honda Accord Hybrid, Toyota Corolla LE Eco, or even just a Nissan Sentra, the Leaf and Volt make no sense (financially) to me at all.
Good point about getting a licensed electrician and checked by electrical inspector. At least in my town, that is a legal requirement. But in terms of comparing costs, rather than theoretical, it might be good to see how one Model S owner's energy costs changed. In my case, my husband and I used to spend ~$200/month for gas. But since we drive more often in the Model S now, he spends less than $50/month on gas (he still has an ICE) and our electrical bill is up ~$50 more per month. But this is probably due to the fact that our electrical rate is $0.07/kwh since we get much of our electricity from hydroelectric and wind power.
Thanks Charlotte. How do you charge at home? Would you mind sharing the cost with us of your installation and the type Tesla charger (on the car) you selected? - For those interested, Charlotte is the Tesla owner profiled on our Tesla page. We are proud to have her a frequent contributor.
I did not get the High Power Wall Connector because my home electrical cannot support it, and I didn't think I would need it. I had a NEMA 14-50 installed at my home for less than $900. However, when the electrical inspector came to look, they found a major problem with electrical to the garage that was done before we purchased the home so that cost more, but I think that prevented any problems with heating or fires.
Yes, I think that is very common. When an electrician works to install a new high power line like this they look closely to see if there are other issues. They don't want to be blamed for prior work that causes issues.