Suggestion: How Tesla could implement Vehicle to Load

[rrolsbe]

Start crazy thinking.

Some Reno homeowners have been without power going on 5 days now with night time temps as low as mid teens. It is a fair bet that at least some of affected home owners also own Tesla vehicles. I know that there are many options for home backup power but none, in my opinion, is better than the following. None of the Tesla vehicles currently have the hardware to support V2L like some of the newer EV's on the market; however, they could produce and sell an external inverter that could convert the HV DC available at the charge port to split phase 240VAC (maybe more than one model). I am sure the Tesla bean counters would be concerned with a accelerated HV battery wear, warranty issues, possible loss of Powerwall sales and other issues. Since Tesla would know how many KWH of energy was exported from the car they could reduce the HV battery warranty miles/time and/or charge an appropriate fee for every KWH exported to cover these concerns. They would also make money on the sale of the inverters. An additional indicator showing a HV battery miles odometer and the reduced warranty period associated with using the car as a stationary power source would also be required. The 90% to 20% energy available on my Model 3 is about 50KWH, that should be enough to get by for at least a week running only essentials devices and supply power to a natural gas furnace. Given the above, owners could make their own decision knowing that their HV battery warranty could be affected and the value of the car when sold could also be reduced. After the HV battery warranty period has been reached, owners would be responsible for any possible battery replacement or reduced value. As a consumer, being able to make informed choices is very important.

End crazy thinking. Thoughts?

 

[RandyS]

Is it doable? Yes, with some software and hardware (the charge port is not currently set up to be bi-directional, along with the limitations you mention with respect to warranty, etc.).

Is it the most elegant solution? Not really, as you mentioned, since Tesla already sells a product that would do this.

A cheaper "available now" solution for low powered lighting and to charge phones/tablets, etc. would be a 12v to 120 VAC inverter that would clamp onto your 12v battery and get recharged by your traction battery. That would give you a few days of low powered backup for essentials and wouldn't cost a lot or require additional charge port hardware or software upgrades...

 

[GSP]

@rrolsbe - I also would like to see Tesla offer V2L and V2G. Your idea to track kWh exported and use it to limit Tesla’s warranty liability should work. Maybe just track battery lifetime total kWh or Ah throughput, and put a limit on that. Either way, make the value accessible on the touchscreen, just like the odometer.

GSP

 

[jkdman123]

Pipe dream, IMO. Elon won't scavenge Powerwall sales, which I'm sure is why this hasn't been done yet.

 

[stopcrazypp]

As others mentioned, not going to happen when it steals Powerwall sales. Also won't happen until Tesla switches to chemistries with higher cycle life (perhaps makes sense for LFP). The Ford Lightning uses a DC to AC solution like you suggested.

Currently the easiest way to use your Tesla for backup power is 12V inverters. For higher power demand, people have clamped to the terminals under the rear seats.

 

[Gauss Guzzler]

• Tesla's onboard AC/DC converter (PCS) is only capable of 48A conversion. To increase this would add cost/weight to every car and slightly reduce charging efficiency.
• Tesla's PCS is only capable of AC -> DC conversion. To do the reverse would add cost/weight to every car.
• The wall charger and its long cord are only capable of 48A...
• Typical home wiring circuits are only capable of 48A...

You generally can't connect your house to a 48A supply. Sure, you might be conscious enough to do it safely, but the general public won't. So the standard installation would involve a second main breaker to be installed with a huge rewiring effort such that some loads could be automatically disconnected when the system switches to battery power. In addition to the main automatic switching system, of course.

So let's say you just happen to get incredibly lucky and just so happen to have a "fully" charged battery (80%) at the time of power failure. And let's say you're willing to risk everything in order to watch Netflix and will fully deplete your battery (20%) if necessary. That gives you 45kWh of energy to use (60% of 75 kWh).

So 45kWh with 90% DC/AC conversion efficiency could supply 4000W to your house for about 10 hours - if the car just happens to be at home and fully charged.

Or you could just buy a Powerwall for about the same price and save your luck for a lottery ticket.

 

[jjrandorin]

So 45kWh with 90% DC/AC conversion efficiency could supply 4000W to your house for about 10 hours - if the car just happens to be at home and fully charged.

Or you could just buy a Powerwall for about the same price and save your luck for a lottery ticket.

I agree with most of what you said, but,

1. The average home is not running at anywhere near a 4kWh run rate per hour, when on grid, let alone during a power outage where people would be trying to conserve. A much more realistic number to use would be 1kWh run rate.

2. Your "45kWh" isnt (1) powerwall, its roughly 3 powerwalls (13.5kWh each)

3. the statement about "risking everything to watch netflix" is obviously hyperbole, and waters down the rest of your statement. People in power outages are usually concerned with things like their fridge.

I say this as someone who has 2 powerwalls along with the associated equipment, etc. it would be nice to be able to use my car to supplement that, which is something I think tesla will eventually do, but one thing I dont think they will ever do is enable straight V2G. They might put a 15v outlet in teslas at some point, but the only way I ever (ever) see tesla implementing any sort of backfeed from the vehicle is in the situation where someone already has powerwalls (and all of the associated auto switching hardware).

Or, Tesla goes out of business and is bought by some other company.

Those are the only two situations I ever see any sort of "run my house off my car" implemented from tesla (powerwall install supplement or tesla sold as a company). No amount of people wishing for it is going to change that imo.

 

[davewill]

• Tesla's onboard AC/DC converter (PCS) is only capable of 48A conversion. To increase this would add cost/weight to every car and slightly reduce charging efficiency.
• Tesla's PCS is only capable of AC -> DC conversion. To do the reverse would add cost/weight to every car.
• ...

This isn't how I forsee it being done. If it were done, I would expect the AC inverter to be external to the car, professionally wired into the house. The only change inside the car would be software to allow the external inverter to be connected directly to the HV battery through the charging inlet. Doing it through an existing wall connector would be insufficient as a feeder like this would need a transfer switch and other safeguards against feeding power outside the house when the power is out.

I also agree that Tesla would never support this, unless maybe they were required to by legislation.

 

[Gauss Guzzler]

A gas furnace pulls about 1kW but with 50% duty cycle that's only 500W. Add in 150W for a refrigerator, another 150W for Netflix... and I agree with your 1kW power consumption estimate. But with electric heating/cooling/cooking/cleaning and common lighting loads of 500W per room several kW is not unrealistic. Certainly not as unrealistic as the assumption that the car will happen to be at home and amply charged at the time.

Extended power outages often coincide with escape-worthy events, so whether it's Netflix or a refrigerator or just basic warmth that you need, there's the issue that you are tapping into escape power to get it. Maybe you'll drain your battery during a wildfire, then have to evacuate unexpectedly and end up waiting 6 hours in a supercharger line in the middle of the night. Or maybe you'll power your house for 3 days during a snowstorm that knocks out power for 2 weeks.

So is it worth it? There's expense, there's hassle, there's risk, and a whole lotta luck needed. And remember, it's not up to you - hundreds of thousands of people would need to be willing to pay many thousands of dollars for this feature in order for it to be economically viable to produce.

@davewill Indeed the car could likely supply 400VDC output with software. But a dedicated external inverter would be very expensive, as would the ~100A wiring run to the breaker panel and associated high power switching system needed to make DC power worthwhile. Nevermind all the UL, NEC, and insurance concerns with grandma getting her Buick snagged on a long pile of 400VDC cables. This would appeal to an even smaller market than a 48A limited system.

 

[davewill]

@davewill Indeed the car could likely supply 400VDC output with software. But a dedicated external inverter would be very expensive, as would the ~100A wiring run to the breaker panel and associated high power switching system needed to make DC power worthwhile. This would appeal to an even smaller market than a 48A limited system.

As you pointed out yourself, that would require fitting an AC inverter inside the car, which is not cheaper than an external one. Trying to then feed the house through a standard WC install, ignores the need for protecting the feed from going outside when the power is out. In short, it's not even an option.

I also see no reason why an external inverter would have to generate 100a AC, or why it would need any more HV switching than already exists in the car. I also know this is how the various existing V2G devices (for other cars) work.

Suffice to say, they are both equally unlikely.

 

[UCIBtheG]

I wonder if Tesla could lock it down so that their vehicles could only transfer energy to PowerWall(s). That would eliminate the PowerWall sales cannibalization that V2X presents, and would actually incentivize homeowners who already own a Tesla vehicle to buy a PowerWall, if they don't have one already.

 

[Gauss Guzzler]

@davewill
The existing 48A inverter could be made bidirectional with some minimal extra hardware and would be vastly less expensive than an entire dedicated external inverter. And the existing wall charger could be made bidirectional with little more than software changes. So if Tesla is to make an economically viable V2G solution, this would be the likely approach.

So if external DC -> AC conversion is more expensive, your motivation would likely be the need for more than 48A. Much more. Probably ~100A so that you don't have to rewire your whole main panel.

Yes, of course any V2G system has to be connected properly, I didn't suggest otherwise. In fact I repeatedly noted that this is a huge and necessary expense that greatly detracts from the cost/benefit equation.

Tesla was once optimistic about V2G as well, but I suspect they concluded with the same cost/benefit drawbacks:

Smarter Charging | Tesla

www.tesla.com

 

[rrolsbe]

Good discussions everyone! For a power outage backup solution only, I could live with a 2 to 2.5KW inverter for other times a 4KW unit could come in handy. My natural gas furnace pulls around 900W so 1KW taking into account an inverter efficiency. I would set the thermostat to around 56F so my furnace should run no more than 20 min/hr (keep the pipes from freezing). We have a gas fireplace in our master that will operate with no power, so can be nice and cozy in there. We also have a wood stove which would supply some heat while cooking on its top surface (do not currently have a large supply of wood). The only other thing that would require power is the fridge; however, ice chests keep outside or in a cold garage would also keep food from spoiling. I have read about connecting a 12V inverter to the terminals under the backseat but that is not the most elegant solution and would only supply maybe 1.5KW max continuous power. Currently, if Tesla detects this setup it could void parts of your warranty; however, after the warranty period who knows what there stance might be (disable supercharging?) I also agree that Tesla doing what we are discussing is unfortunately a pipe dream but you can also hope.

Regards

 

[jkdman123]

I wonder if Tesla could lock it down so that their vehicles could only transfer energy to PowerWall(s). That would eliminate the PowerWall sales cannibalization that V2X presents, and would actually incentivize homeowners who already own a Tesla vehicle to buy a PowerWall, if they don't have one already.

That's not a bad idea. You should tweet it at Elon and see what he says. He may just hire you on the spot!

 

[ucmndd]

Yes, of course any V2G system has to be connected properly, I didn't suggest otherwise. In fact I repeatedly noted that this is a huge and necessary expense that greatly detracts from the cost/benefit equation.

I don’t think it’s a “huge” expense nor insurmountable hurdle. Tesla’s energy gateway for Powerwall installs has probably 90% of what’s required already. We’re basically taking about a semi-intelligent automatic transfer switch.

Ford has more or less figured this out with the Lightning - as I recall it’s about $4k for the home charging station with the built in brains and ATS to make this happen.

Expensive? Sure. Expensive within the context of an $80k truck or in comparison to ~$20k for two powerwalls with a fraction of the energy? Nah.

 

[MP3Mike]

This isn't how I forsee it being done. If it were done, I would expect the AC inverter to be external to the car, professionally wired into the house. The only change inside the car would be software to allow the external inverter to be connected directly to the HV battery through the charging inlet. Doing it through an existing wall connector would be insufficient as a feeder like this would need a transfer switch and other safeguards against feeding power outside the house when the power is out.

And that is exactly how the Ford Pro Power system works to provide power to a home. Their wall connector has the capability to pass the DC through to a inverter/transfer switch, which of course you have to buy/install as well. I think it even includes a small battery to help run things when the grid is out until you get your F-150 Lightning hooked up. (And I think the total cost for that comes in around $7k.)

 

[father_of_6]

I just want to add that during the recent heavy blizzard, our power went out for about one day. The temperature dropped down to about 40°F in our house. We weren't concerned for survival, but it wasn't pleasant either. We're not a good candidate for solar, and last I checked they weren't selling powerwalls without solar panels.

It was a bit sad knowing that we had a Model 3 sitting in the driveway at 60% charge, but no electricity available to power our gas boiler to heat the house.

 

[rotarypower101]

People that are interested in V2L (ignoring all the outside factors of why it's not include), assuming your purchase price is not extravagant already, how much "dollar" value would that add to a EV to have V2L functionality built right in? Especially if it was intelligently integrated/managed through the same home charge point to make a brief home outage virtually invisible to the end user even if restricted/or a modest output?

Furthermore when traveling or camping having that power avalible for whatever purpose might be needed.

 

[BigNick]

I just want to add that during the recent heavy blizzard, our power went out for about one day. The temperature dropped down to about 40°F in our house. We weren't concerned for survival, but it wasn't pleasant either. We're not a good candidate for solar, and last I checked they weren't selling powerwalls without solar panels.

It was a bit sad knowing that we had a Model 3 sitting in the driveway at 60% charge, but no electricity available to power our gas boiler to heat the house.

Rochester, NY would be a better candidate for wind power, with Lake Ontario just to the north.
Provided the turbines don't freeze up from lake-effect snow!

Tesla being chiefly a California company thinks every place has abundant sunshine 12 hours of the day.

 

[jkdman123]

I just want to add that during the recent heavy blizzard, our power went out for about one day. The temperature dropped down to about 40°F in our house. We weren't concerned for survival, but it wasn't pleasant either. We're not a good candidate for solar, and last I checked they weren't selling powerwalls without solar panels.

It was a bit sad knowing that we had a Model 3 sitting in the driveway at 60% charge, but no electricity available to power our gas boiler to heat the house.

There are other companies that make home batteries. You're not relegated to only using Powerwall.