Tesla batteries as backup to power homes?

Tesla batteries as backup to power homes?

I read an article in Forbes on-line magazine on August 5, which said Nissan had revealed plans to power homes with electricity stored by the lithium ion batteries in their LEAF vehicles. Here's the link: Assuming this is true, that is a really good idea. Is there any reason that Tesla could not offer the same thing? I've been shopping for a backup generator for awhile but being a model S reservation holder this would be a much more environmentally friendly way to keep my home powered for a few hours (or more) during a power outage. Power outages in my area are infrequent ( 1-3 per year) and they typically last 2 -4 hours (one last year was 24 hours). I think this could be a great secondary use for Tesla's battery technology.

Does anyone else see promise in this? For you electrical types out there, what equipment would be needed besides an automatic transfer switch?

VolkerP | 17 augustus 2011

I assume the backup power should kick in on a power outage, when your Tesla is parked in your garage. This setup requires the automated switch you mentioned and a fair bit of control circuitry in the car, as well as a connection between them. The car must detect a power outage. The switch must tell the car that he has isolated the home from the power grid. The car then has to establish what is called an electric "island net" where the PEM controls voltage and frequency and must deliver the required power as needed by your home (e.g. an AC unit is turned on and starts to draw 30 Amps). It must protect the car battery from overheating and from complete discharge.
If grid power returns, the automated switch and the car must work together to disconnect power supplied by the car, then switch back to the grid.
Sounds like additional signal contacts in the charge plug which is usually hard to get them included in updated standards.

Tesla Motors stated on the subject of V2G ("vehicle to grid") that a "life" car battery is much to precious to waste charge cycles on a daily base. Used car batteries may face a second life as V2G or emergency backup units in stationary installations. The Mennekes plug provides signal contacts intended for V2G, I am not sure if they could be used for the "emergency backup" scenario.

TonyF | 17 augustus 2011

Thanks for the insight, VolkerP. Setting this up sounds more complex than I envisioned. I like your idea of possibly reusing old Tesla Batteries for home electrical backup by setting the battery system up somewhere in the home. If we switch out batteries from our car and they still have 40% or 50% of original energy storage, and if we assume that new batteries will be able to store, say 50kwh of energy, that leaves 20kwh or 25kwh of storage which can keep critical things powered for a few hours.

Well, since I plan to keep my batteries for 7+ years, looks like I should get back to shopping for backup generators.

VolkerP | 19 augustus 2011


consider to invest in a roof mounted PV system. It will supply you with "miles out of sun rays" when you charge your Tesla from it. Many Roadster owners do so. I understand that in some federal states there are incentives that make such PV systems pay for them self.

Concerning emergency backup, this is not possible with a standard grid-tied PV system: The inverter cuts off the solar generator if he detects a grid power outage.
However, some people beefed up their systems with a battery bank, an automated mains switch and enhanced inverter to serve as an emergency power supply. You could still run critical things from such system, but plugging in your EV would make little sense. This beef up will add considerable cost to the system, which will exceed the cost for a backup generator and for which you possibly will get neither incentive nor return on investment, though.

Brian H | 19 augustus 2011

Volker: you're going Germanic with your pronouns here and there; in English, "he" and "she" apply to living things only, where you know the sex. All objects and abstract concepts get "it". Unlike Germans, we don't have sexual urges towards every object in the universe.

Brian H | 21 augustus 2011

Volker: you're going Germanic with your pronouns here and there; in English, "he" and "she" apply to living things only, where you know the sex. All objects and abstract concepts get "it". Unlike Germans, we don't have sexual urges towards every object in the universe.

VolkerP | 21 augustus 2011


acknowledged. This chance to improve my English is greatly appreciated.
What is the sex of the statue of liberty? Or USS Enterprise (CVN-65)?
Anyway, thanks for keeping this thread up high in the forum!

Timo | 22 augustus 2011

I think all ships are female, not necessary in official language, but ask any mariner about his ship and he tells you that "she" is this and that. So USS Enterprise would be "she".

Vawlkus | 22 augustus 2011

Exceptions to the rule Volker! :P

Ramon123 | 22 augustus 2011

Well, let's see here. Here we have a suggestion to spend God knows how much to install backup capabilities for your home. We have to assume that Nissan's suggestion was prompted by the desire to wring some more profits out of their Leaf. Some backup battery - a large part of the time the car won't be available at the house (during the hours when most power failures occur) and when it is it will likely be recharging itself, so may be low on electricity. So if power goes out, most likely either the car is not there, or not hooked up as a backup. Yeah, sounds good to me. Especially the added expense.

Brian H | 22 augustus 2011

the dupe post was the result of the hangup of the new spam filter redirect me to a "Maintenance" parking lot. Then I got around it, reposted, and then the original came thru. >:(

As for objects with gender, I can think of a few cases where "she" is used as a kind of sign of affection, but none of "he". Interesting.
As for EV-backup house power, I think the complexities referred to already mean that it's a non-starter. But prob'ly some gubmint money will get poured into it somewhere so some installations will happen. We'll see.

Brian H | 22 augustus 2011

The estimated battery retirement capacity is around 70% at 7 yrs or 10,000 miles. What few numbers have been reported to date say that's realistic, or even a bit conservative.

But I expect LiIon technology to be utterly transformed by then.

VolkerP | 23 augustus 2011


one of your numbers is way off. It is 100,000 miles instead of 10,000. Many Roadsters have passed 10,000 miles, one has passed 40,000miles.

Brian H | 24 augustus 2011

yep, sorry. That's what I thought I typed.