Home Backup Power - New Feature Request

Home Backup Power - New Feature Request

Occasionally we'll have power outages to go along with winter weather at my house.

It occurred to me while investigating backup generators for my house that I have an extra 60 kWH sitting in my garage right now, enough for a day or two of backup power. Would it be possible to draw from the battery back through the wall connector as a battery backup? Obviously you'd need to install a transfer switch and shut off the mains in the house so you don't feed the whole neighborhood, but I'm wondering if the charging hardware in the car could function in reverse.

Sudre_ | December 5, 2013

This would be a neat idea but I know each utility provider would have different restrictions. Since a qualified electrician and permit would not be required for you to plug the car in and use it anywhere as a generator, I don't see this idea taking off until NEC (national electric code) is updated with revisions to include BEV doubling as generators.

If you get a generator for your house, technically, you are supposed to get a permit before wiring in so everything is safe and the transfer switch is wired correctly.

With a car your buddy can borrow it. Plug it into his drier outlet and back-feed the grid killing a line worker. "Well I didn't know I had to turn the main breaker off"

Secondly the male metal prongs coming out of the UCM that are normal plugged into the wall would become hot when in generator mode. This is not legal to do. The whole plug system would have to be redesigned.

stephen.pace | December 5, 2013

This is called Vehicle to Grid (V2G) and Tesla offers no support for it. People have asked them about it before and I think it got a 'this is a very low priority option for us' type of answer. See:

Keep in mind that use of the batteries degrades them slightly over time, so if the power company could use your car to load level it might be good for them, but not so great for the long term fitness of your battery.

Note: not the same thing, but plans to offer options for On-Board Power Export Inverters for their trucks. That way your car could power your tools instead of towing or carrying a generator to your work site.

Roamer@AZ USA | December 5, 2013

Nissan has already done it.

The back feed problem could be easily solved with electric meters that incorporate a disconnect relay that breaks the connection if supply line power is not hot.

Just like AT&T stopped phone innovation for years with monopoly control the electrical utilities will stifle innovation until they are forced to open up and compete. After breaking the AT&T monopoly phone innovation exploded, fax, answering machines and ultimately modems and the internet.

The generation, sale and supply of electricity is poised for big changes in the future just like phones and the internet.

Look forward to the day that my Tesla will back power my grid tie solar panel inverters and make power failure or interruptions painless.

Docrob | December 5, 2013

Sudre, your fears are unfounded, of course you would NEVER allow it to feed back into a standard drier outlet. Any such system would rely on a smart interface via a two way inverter that would act as both charger for the car and smart management of any power drawn from the car. The car would detect that it had been plugged in to this device and the device would control the flow of power to and from the car to remain safe at all times.
Anyone with solar panels can have a battery backup that gives them uninteruptible power in the event of a grid failure and allows them to continue to use their solar array output, these "island" solar inverters meet all the relevant safety codes and there is no reason a similar device couldn't be developed to interface with the batteries in the Model S. UPS functionality is one possible role feeding power only back into the home it is connected to in the event of a grid failure. V2G technology however has far more potential that that with the possibility of feeding back into the grid itself at times of peak demand providing a very valuable peaking supply service in return for a financial return to compensate for the extra wear on the batteries and the value to the utility.

stevenmaifert | December 6, 2013

Nice idea but... Read your warranty. Using ModS as a stationary power source is not allowed.

kback | December 6, 2013

This seems a little crazy to me. During power outages, people are often desperately looking for gas to at least keep their cars powered up, and instead you would want to intentionally drain your car battery, and potentially leave yourself stranded, when your house is without power? I went the other way, and bought a generator to power my house and charge my Tesla!

Big T | December 6, 2013

kback, same here. The last local disaster left us without utility power for 2 weeks and gasoline was scarce. A major reason for me to purchase a Tesla was that I can generate all the electricity I need to power my house and charge my car.

Tessnme | December 6, 2013

What if you plugged an inverter into the 12volt outlet and powered some small appliance for a while? Would the 12 volt battery renew itself from the main battery or would you just quickly deplete the 12 volt and be unable to start your Tesla?