Using my 90D as emergency power for my house?

Using my 90D as emergency power for my house?

I'm not super interested in buying the new Tesla powerwall since it is actually not in my interest to store day solar energy to power my house at night. I benefit others (and my bill) more by sharing it during the day when it can be used by others.

But, I would be interested in having my car that's already plugged into a 50A circuit, be able to power my house if I lose power for some reason.
Obviously this would be rare, so it wouldn't be much of a burden on the car's batteries since it would only happen once a year at most.

I realize there are load and inverter considerations, but quite frankly 50A 240V is _more_ than enough to power all my house and 90Kwh is about 3.5 days' worth of electricity for my house without any load shedding.

Is that something Tesla has been considering at all, or not really?


NKYTA | 22 November, 2015

Not really. Soon, maybe, but probably unlikely.

carlk | 22 November, 2015

There is no reason it can not be done. The powerwall setup is more than half way there of what you want to do already. I think "soon" is probably the most likely scenario.

PBEndo | 22 November, 2015

Considering Superchargers (and often other chargers) are free, I would anticipate some resistance to letting you power your house with those free electrons.

Mark2131@CA-US | 22 November, 2015


What you're asking for is called "V to G" or Vehicle to Grid. Current hardware on Tesla's do NOT support this. However, it is entirely possible that future models WILL do this.

All of the naysayers who claim that electric cars will suck up all of the available electricity out there fail to note that a large fleet of batteries distributed nationwide can actually ENHANCE the electric utilities ability to handle such a load. If you think Tesla has been disruptive to the automobile industry, just wait and see what happens to the Utilities once "V to G" becomes a reality.

We certainly do live in interesting times!

f-tal | 22 November, 2015

I believe the Tesla warantee expressly prohibits using the car as a power source. | 22 November, 2015

Actually, with a little change to Teslas' in-car software, the Model S could do V2G and/or power a house. What is required outside the car is an inverter box to convert the 400V DC to 240 VAC and some critical safety electronics. Tesla could even deal with free Supercharger power with some payback method if you end up using Supercharger power for V2G or powering your home (this is a non-trivial software task).

To power the house when the incoming house power is dead does require additional electronics to disconnect the house mains from the incoming power line. This has to communicate with the inverter to ensure you are not powering the neighborhood (and possibly electrocuting the line workers). All doable, but not a trivial or cheap system.

I do expect we'll see such an option in the future.

V2G systems have the ability to actually make you money from the power utility company. They basically will pay you to use your battery power so they don't have to spin up a very expensive peaker plant during peak demand periods. This is all done by remote control and you can set limits (i.e. set hours, days or State of Charge limits) so that you have sufficient battery SOC when you need it.

prp | 22 November, 2015

Will never happen for two reasons;
Firstly tesla would be paying your home power bill via superchargers, and noting some countries pay over 35c per kwh.
Secondly every cycle takes battery life, so someone that did the home power thing daily would halv the life of the car battery. Press around tesla cars having 4-5 year battery life would not be good.

marc | 22 November, 2015

You all bring good points about the supercharger to house problem, and note that I'm not trying to use my car to power the grid, only to power my house if power is out.
It would be trivial for Tesla to limit this use to 24H and 3 times a year or somesuch. This would stop people from stealing from superchargers. Also, let's be reasonable, but someone who just bought a $100K car probably has better things to do than to steal power 50kWh at a time, which is the full sum of $5 to $10 :)

But, I just realized that it may be harder than I thought to stop the power from the car to go back into the electrical pole and power my neighbors, especially since I already have a system that sends power back to the grid for my solar panels.
I would need to manually disconnect the circuit breakers that feed to the utility pole, and then it be a bit harder to know whether power just came back outside of looking at my neighbours.

As for the others who talked about using my car to shift peak load, I explicitly stated I didn't want to do this since it's a bad use for my car's expensive batteries, and also that's exactly what powerwall is supposed to do anyway.

s.grot | 22 November, 2015

You could install a dynometer in your garage floor that is connected to your house; when the power goes out just jump in your car and set cruise control to 20 mph; the dynometer will generate power for your house

mechapreneur | 22 November, 2015

It seems financially absurd to use a $100k car plus inverters (or you could use the on-board car inverter?) to power a house instead of a $3.5k power-wall battery and inverter.

Even setting aside the costs for a moment, you are going to put additional strain on your vehicle's energy systems by turning your refrigerator on/off, and when you burn out your vehicle's system, you are not only out of power, but out of transportation.

Just get solar/power-wall.

marc | 22 November, 2015

mechapreneur, I already have solar :) and power wall is too small. 7Kwh? My panels make that in 1.5 hours or so.
Powerwall is fine for load shifting, but not for powering your house should you need to once a year or so.
As for having yet another set of batteries that need to be conditioned, and only use them once a year at most? That feels wasteful to me :)

And I'm not sure why using up to 2Kw would put much strain on a battery system that puts out a lot more and is designed for rapid accelerations (i.e. power delivery).

But ok, fine, I'm an engineer, I think too much and I like for all things to be used to the best of their abilities. I'm guessing there isn't enough demand and maybe Telsa has bigger fish to fry than to cater to that use case (but please prove me wrong, I'll be happy to eat those words :) ).

s.grot | 22 November, 2015

Marc, don't worry about being wasteful with the powerwalls; I figure those powerwalls are made up of used MS batteries anyway | 22 November, 2015

Just cut to the chase and use the MS as your emergency house.:-))

Linus | 22 November, 2015

>>> Also, let's be reasonable, but someone who just bought a $100K car probably has better things to do than to steal power 50kWh at a time, which is the full sum of $5 to $10 :)

If that was true then why do we have a thread with a gazillion posts about locals (ab)using SCs?

plafor | 22 November, 2015

Having the option for the Models S/X to produce standard 120 Volts AC power would be another significant advantage over ICE cars. A NEMA 5-20 plug (120 V, 2 Kw) could power appliances during camping trips or at home using an extension cord (no risk of affecting the grid). It could also provide emergency charging to other EVs with low state of charge.

A NEMA 5-20 plug would not be able to power a whole house and therefore reduce the risk of people overusing the Superchargers. Anyway, Tesla could include extra cost for use of Superchargers (another $2K may be) in the price of a NEMA 5-20 plug option.

I would not be surprised if the other car manufacturers includes such an option in their future long range EVs as it is relatively easy/cheap to produce. So it would be advantageous for Tesla to come up with the option first rather than eventually play catch up with the other car manufacturers.

NKYTA | 22 November, 2015

@george, here in earthquake country, that's where I keep my computer backup! ;-)

Red Sage ca us | 23 November, 2015

Tesla Motors has no interest in V2H or V2G systems at all. As someone who grew up in a place that had lots of bad weather and tons of power failures, I'd rather the energy were still in the car, so I could drive a State or two West before Tornado/Flood Warnings came to fruition. Would you really siphon gasoline from your car to run a generator at home? Of course not.

Tesla-David | 23 November, 2015

@marc There are two versions of Powerwall, 7kW and 10kW. The 10kw version is for backup incase of power outages. I have one ordered for my home. If 10kW is insufficient buy two or more, whatever you need to comfortably run your home during an outage. | 23 November, 2015

Actually I heard JB talk about V2G several years ago (sorry, no idea where). Tesla clearly has some interest in this, but I suspect the added costs and possible reduction in battery life has shifted them away for it for now (and created the Powerwall instead).

I have maybe one power failure every 3 years, usually lasting less than 3 hours. I had a generator at one time, but never used it (and I'm sure the gas went bad if I had needed it). V2H (Vehicle to Home) still would be slick, especially for infrequent events.

I like the idea of having it limited to 3 times a year so such, which limits any Supercharger abuse and shouldn't affect battery life. Clearly if you need V2H for many times a year, then Tesla would need some type of reduction in the warranty and some way to prevent Supercharger/Local charging from being used to power houses without compensation.

I'm sure it can be done by Tesla, but likely not worth Tesla's effort now that they have the Powerwall. The owner's cost might still be $1-2K for the extra inverter, so perhaps few would buy it.

marc | 24 November, 2015

@s.grot, yes I know powerwalls are made out of used batteries, but as I and others mentioned, I feel a bit silly buying even that if I'm going to use it once a year, or less.
It's actually not even sold to run your house off the grid last I checked, but only to do load shifting and benefit from time of use pricing (which is exactly what I already do with solar panels, and my bill is already negative, so more load shifting with a powerwall is just going to be a net loss for me).

Tesla-David | 24 November, 2015

@marc, as I stated above there are two versions of Powerwall, see the last sentence pasted from Powerwall link. "Each Powerwall has a 7 kWh energy storage capacity, sufficient to power most homes during the evening using electricity generated by solar panels during the day. Multiple batteries may be installed together for homes with greater energy needs. A 10 kWh weekly cycle version is available for backup applications"

marc | 25 November, 2015

@Tesla-David: I understand what the powerwall does, but I think you don't understand that I would be losing money if I did that (not counting the price of the powerwall), at least in California where I live due to time of use pricing, I make more money selling the electricity when I produce than storing it and using it at night when it's worth 2/3rd less (more or less).
I understand you may live elsewhere and this may not be true everywhere, but in my case the powerwall is a double net loss of money (price of powerwall and price of money lost by storing my electricity instead of selling it back to the grid).

Tâm | 25 November, 2015


There is no reason that you cannot do what you described.

Because you can indeed, so there is a

Warranty exclusion:

"Using the vehicle as a stationary power source;"

marc | 25 November, 2015

I think I need to change my user name. There are too many @marc users. (Posted by the @marc use who did not start this thread).

compchat | 26 November, 2015

You should have bought sunny boy inverters for your solar power. They allow you to draw off 1500 watts per inverter during a real or simulated grid outage. There's a drop down switch/plug that you turn on during a power outage. Then you plug in your emergency load. I expect you could send the load to a subpanel for distribution to your emergency load; however that is not how it is configured out of the box.

I'm still awaiting my installation. I'm buying an 11 KW system which would give me a total of 3000 watts during a grid outage. This would be at 110 volts which calculates to around 34 amps AC (single phase) using a power factor of .8

I(A) = P(W) / (PF × V(V)) | 26 November, 2015

@marc & @s.grot, "yes I know powerwalls are made out of used batteries"

I think s.grot was saying they may be used, not that they are. I've never heard this before and I strongly doubt it.

Tesla would have to state that the batteries are not new and I doubt they have so many used batteries in just the right condition for the Powerwall. When you create a pack (car or Powerwall) you really want all the cells in a module to be almost identical, otherwise you get imbalances that shorten the life of some cells.

Because of the different use case, the cell chemistry may be different than the Model S as well, so used Model S batteries may not make for an effective Powerwall.

bp | 27 November, 2015

We are considering a 10KW PowerWall for our house - to help with both long (hurricane) and short power outages.

If there is a hurricane, we could be without power for several days - and while it's tempting to use the 85KW battery in our P85 to power the house - if we may not be able to easily recharge our P85 for several days - we'd probably want to conserve every bit of power in the car - for as long as possible - and not risk depleting the power and getting it stuck at home until power is restored.

erickd1 | 27 November, 2015

I wonder how long it will take to catch the spammer(s)/hacker(s)? And I wonder if it is a disgruntled member who got pissed at someone on the forum?

marc | 28 November, 2015

@Teslatap: you are correct. I assumed powerwall would be used batteries, but maybe they're not.
That said, it's orthogonal to my main query :)

If you used 10KWh from your P85, you'd have 70KWh+ left in your car. Whether you'd want to use more or not during an outage is up to you. All I'm saying is that it'd be good to have the option.

Again, I can't justify buying a 10KWh battery which I will use virtually never (actually keeping lithium batteries charged forever without even using them, isn't that good for them), when I have a perfectly good 90KWh battery sitting in my garage and could use it very occasionally without damaging it or shortening its life for its main purpose.

@compchat: yes, it's regrettable my solar inverter cannot partially power my house when utility power is gone

simon | 16 July, 2016

in Adelaide Australia we have a high dependence on wind power and as such we have frequent and inconvenient
power outages. To use my Tesla as as a back up power unit for my home would be fantastic.
If Tesla are not looking at this someone else should .

rharris | 16 July, 2016

I don't know if this has already been posted, but I did see a EV model from BYD that allowed you to do just this. The car had a 240v outlet that you could use to draw from the battery pack.

Caterham7 | 13 September, 2017

Wish I could of used my $100,000 Model S this week to power just my AC after Hurricane Irma

radami2 | 16 June, 2018

It seems some enterprising electrical engineer like a young Elon or JB Straubel could design an interface between the inverter of the Tesla and a 240v outlet anywhere on the car such as in the frunk. THE inverter could send out a const 60hz at either 240 or 120. The inverter already gets its energy from the battery. Good ole Rich from Rich rebuilds could show him how it's done. It seems like there would be big money in an aftermarket product since Tesla won't do it. It would actually be superior to power wall for a power backuo since it would have many times the reserve. It would also be cheaper since it doesn't require a new battery or inverter. Just requires a competent installer like Rich and an EE.

SO | 16 June, 2018

I’d rather just buy a separate $500 generator vs hooking up my expensive car as a power source.

murphyS90D | 17 June, 2018

The inverter generates variable frequency 3 phase power at high voltage. Tesla won't do it because the cheapskates among us would charge their car at a supercharger and then use it to power their house.

Mi75d | 17 June, 2018

Dear Tesla, I would absolutely pay money for this option. Elon, here’s what you need to do: have an engineer design a special wall option that interfaces the house electrical panel with the car and with Tesla. When the power goes out, the owner hooks the car up to the house, powering it. When the owner goes to the Supercharger, the power is paid for by the owner at the usual rates.

I would pay for this as long as I cost less than a small in-house generator.

Yodrak. | 17 June, 2018

"When the owner goes to the Supercharger, the power is paid for by the owner at the usual rates."

The "usual rates" being zero for many (most?) Model S and X owners, you expect Tesla to pay for the electricity to power your house during a utility power outage?

radami2 | 17 June, 2018

All you folks who want a small gas generator have obviously never used one. You only need them once or twice a year so when they are needed, half the time they won't start, they stink, they have to be outside unless you're a fan of asphyxiation, they are very limited in what you can do with them because you need a ton of extension cords. As far as the battery warranty is concerned , they will start running out in a couple years with the batteries still full of useful life. I can charge at home and I would trade my free supercharger use for the convenience of being able to use the battery as a backup or an off-grid power buffer. All that stuff about 3-phase variable blah blah is all software controlled so the basic stuff required for a domestic power source is still there.

EVRider | 17 June, 2018

Since Tesla already sells a way to power your home from a battery -- the Powerwall -- I don't see any incentive for them to let people use their car's battery pack for this. Sure, it would be nice in a pinch, but not likely to happen.

barrykmd | 17 June, 2018

murphyS90D | June 17, 2018
Tesla won't do it because the cheapskates among us would charge their car at a supercharger and then use it to power their house.

Especially at JFK.

ss2017 | 3 November, 2018

This feature should help Tesla remain competitive (what-if tomorrow Jaguar or Porche provide this feature - maybe fairly simple to implement as an emergency feature)
Tesla has the visibility to how their car batteries are used. So they can easily control the abuse.
If this is an upgrade - frankly I may pay a few thousand (3-6k - something less than a power pack) if my Model X can be upgraded.

billUK | 3 November, 2018

The vehicle warranty specifically excludes use as a stationary power source.
In this country it is illegal to use take power from a PV solar panel system when the mains fails, the system must shut down.
The Tasla Powerwall adverts specifically say that the system can not be used to power a house in the event of a mains failure or if a house is off the grid
If you use a UPS or other system to obtain power it must not be connected to the mains.

I suggest that you forget the idea, it is a great theory, but is specifically excluded. Buy a generator and stick it outside with what ever you want to run plugged into it directly or via a waterproof extension lead
Nissan is talking about allowing the use of Leaf batteries to supply power to the grid through special systems. However you should note the different warranty period for leaf and Tesla batteries.

lilbean | 3 November, 2018

If this was possible, all the cheapos would be supercharging constantly just to power their homes. Tesla isn’t responsible for powering anybody’s home for free.

bill | 3 November, 2018

It should be possible for Tesla to know if the power in the battery came from a Supercharger (by knowing how it was charged to its current level) and charge you for the power drained.

If other manufacturers start adding this feature then you may see it.

ss2017 | 3 November, 2018

BillUK, Of course I do have a generator that uses gasoline. 3 year old. Ran once. I am not sure it will run again when I need it next time. But I know I have 100 kWh battery sitting idle in my garage :).

If Tesla does not add this feature because of regulations, they may be okay. But having a product like powerwall should not be the reason for not adding this feature. Because then other ev manufacturers will add this feature to their car and that will hurt Tesla.

ss2017 | 3 November, 2018

BillUK, Of course I do have a generator that uses gasoline. 3 year old. Ran once. I am not sure it will run again when I need it next time. But I know I have 100 kWh battery sitting idle in my garage :).

If Tesla does not add this feature because of regulations, they may be okay. But having a product like powerwall should not be the reason for not adding this feature. Because then other ev manufacturers will add this feature to their car and that will hurt Tesla.

sly | 7 March, 2019

Nissan all ready come out with a V2G system. In the US is Fermata Energy who done a pilot program and I believe by now its ready for the public. Tesla should do the same. Model 3 owners dont use free Super chargers and probably for Tesla would be easy to monitor and make to pay for the V2G use of any TESLA.

akikiki | 7 March, 2019

Why should Tesla do the same?

murphyS90D | 8 March, 2019

A whole house generator running on natural gas or propane is a whole lot cheaper than a Tesla.

acegreat1 | 8 March, 2019

Akikiki why not?