In practice you'd never allow your operator to drain you to 0, so 2 cents is very much on the high side.
In the California Tesla VPP trial, they pay 50 cents per kWh.
(correction: 20cents wear, not 2cents)
$12,000 (Model Y bat replace cost) * 300(miles for full drain)/300,000(total miles per pack)
= $12 per cycle
Edit: or 18 cents per kWh
Dunno where I got my 2 cents from, that calculation was done 2 months ago.
That is interesting, that means for home-charging your electric cost (per mile) is about equal to the battery degradation cost.
Thats 2x cost than most think.
In any case I'm getting 10-20 cents depending on battery pack size and chemistry.
What about the remaining 10X? The calculation you’re doing isn’t the right one, because the battery wear isn’t directly related to miles driven; Tesla’s battery warranty is pricing in a “full stack” picture of battery degradation while actually driving.
Your computation implies that the battery has 0 value after ~1000 cycles, but battery manufacturers commonly warranty 3,000-5,000. In addition, cycle count is only one variable affecting degradation, others include the depth of discharge, the charging and discharging profiles, the thermal management, etc.
(This is one reason why a 10-year-old Tesla has noticeably different battery degradation than, say, a 10-year old Nissan Leaf, which has no thermal management and a very poor BMS)
Finally, even when battery degradation occurs, it doesn’t remove the battery’s entire capacity, so degraded batteries can still be used for stationary storage applications. While an extreme degradation like 50% is very bad for an automotive application, it doesn’t matter so much for small-scale grid storage, since space is usually not the limiting factor.
The $12,000 battery pack replacement cost is current market price, including any recycling or potential reuse of old pack.
Edit: actual battery replace including labor is $16,550 from a receipt https://www.currentautomotive.com/how-much-does-a-tesla-mode...
Edit: from the paper:
> We assume the home charging power as 1.92, 6.6, 22, and 1.92 kW for small, mid-size, large BEV, and PHEV, respectively
I don’t think the 22kW assumption is reasonable, but the others are comfortably within current L2 AC charging rates.
On US ebay I see model 3 batteries for $5k
A BMW engine (the b58) is about $5k used, about $10k rebuilt, and somewhere above $20k new.
Regardless, if you do have a high mileage ICE car that you want to save, the used engine is probably the way to go, and won't suffer a crippled range of a used battery.
In general, I like the idea of electric cars, but battery packs are not on the same level as an ICE engine in terms of replacement. If you're in the unfortunate position of owning something like a Volt, odds are you literally will not even be able to get replacement battery- and if you could, it would cost more to buy and install than the car would be worth when you were done. That exact scenario hit the news at least twice in the last year.
And using batteries to smooth out the leaks will allow greatly reducing the peak size of equipment for T&D.
Additionally, look at wholesale markets for electricity, such as Texas', and you will see price swings during a day far far in excess of 18 cents/kWh. This indicates that storage is extremely economical today.
Lifepo4 batteries > 50kwh should easily handle 500,000 miles.
Higher performance lithium ion will degrade at a rate faster than any expected return from a scheme like this.
At least in Northern California it’s now cheaper for me to run solar+battery off grid than to pay pge. Lifepo4 pushes it over the edge into profitability.
If off-grid is competitive, selling at peak prices is a no brainer.
New LFP chemistries that are heavier but more stable are ideal for stationary storage and high cycle counts, but the evidence shows in general that these packs are built for longevity (with very occasional early failures). You could probably do well buying a salvage Tesla and shucking the pack for working modules and coming out ahead economically (safety warning, do at your own risk, etc) if you don’t want or can’t get dedicated stationary storage (although it comes with generous federal, state, and utility subsidies in California).
I installed stationary LFP batteries (from Enphase) on my house in CA 1.5 years ago, but I then discovered that the state and utility subsidies [1] only apply if you are in a very low income (for CA) bracket, have a health condition that requires backup power, or live in a high fire risk zone.
I don't qualify for the first 2 categories, and my luck is that the high fire risk zone starts about a mile away from my house, so good from the fire risk perspective, but not for the subsidy. Still got the 26% federal tax credit (with IRA, it's now back up to 30%).
1. SGIP: https://www.cpuc.ca.gov/industries-and-topics/electrical-ene...
I'm particularly interested in whether you're doing any load-shifting with them, and if so, how easy it is to do with the software. I'm paying $.90/kWh at summer peak, so while I'm still on net-metering, I'm somewhat interested in going ahead and fully arbitraging during peak.
I'm mostly happy with them. The batteries are pretty much set-and-forget, but I change the reserve level by season (90% in winter, 30% in summer). The system automatically decides how to do load shifting to optimize for your particular rate structure. I will say the monitoring software can be janky at times. It's gotten better, but sometimes it is very slow to connect to the system.
> I'm paying $.90/kWh at summer peak
Whoa, where is that? That's 2x more expensive than California or Hawaii. You must be on a wholesale rate plan with very low off-peak rates if you are considering arbitrage. It's also good that you waited until this year, because before the IRA, the residential battery tax credit was only available if you charged it with on-site renewables, not from the grid.
I don't do any grid arbitrage in the sense of buying low and selling back to the grid from my batteries when rates are high. That's not possible for homeowners in CA, is it in your area? However, several places in Southern California already have home-battery based virtual-power-plants that you can participate in, and I think it integrates with Enphase batteries. In those programs, the arbitrage is managed by a 3rd party company which then compensates the homeowner.
However, my evening loads during the peak rate hours do draw on my battery until it hits its reserve level, so what I do is more like peak-rate avoidance than arbitrage.
My batteries also don't charge from the grid, just from my PV array. With subsidized net-metering 2.0, the difference between peak and off peak for me is only $.07/kWh, so there's really not a ton of economic value there, maybe like $70-80/year at most.
My off peak rate for charging the car went from net $.15/kWh to $.36 during the summer.
It’s news to me that load shifting (if you’ve got batteries and solar) isn’t allowed by the CPUC, that does take the wind out of my sails a bit. But the peak rates are so high that just zeroing out my peak consumption is still probably worth it.
Does the system come with a “disconnect from the grid during emergencies” shunt?
I’ve heard conflicting reports about the availability and legality of those systems.
I live in the same service area. The peak EV2A rate (including both generation and distribution) is currently $0.55/kWh, and the off-peak is $0.24/kWh.
https://www.pge.com/en_US/residential/rate-plans/rate-plan-o...
Not sure where you are getting $0.92/kWh, but would be curious to learn.
> It’s news to me that load shifting (if you’ve got batteries and solar) isn’t allowed by the CPUC, that does take the wind out of my sails a bit. But the peak rates are so high that just zeroing out my peak consumption is still probably worth it.
Load shifting in the sense of shifting your load to different times to consume cleaner/cheaper electricity from the grid, is fine and even encouraged by the CPUC. There are all kinds of programs to encourage this. You can achieve this by simple behavioral changes, timed appliance runs, or by using battery storage.
What you can't do as an individual homeowner, AFAIK, is arbitrage power by buying low from the grid and selling back high to the grid later.
> Does the system come with a “disconnect from the grid during emergencies” shunt?
> I’ve heard conflicting reports about the availability and legality of those systems.
The only "emergency" that causes a disconnect is a power outage. That's no different than what solar inverters already do. The difference with the batteries is that when that happens, they form an isolated microgrid on your premises, thereby providing backup for that scenario.
What other sort of emergencies were you imagining? If you mean minimizing grid load during peak grid load events, then that's what the virtual peaker programs do, and those are completely legal, and active participants in the CAISO energy markets.
My peak generation charges were a further $.31/kWh.
I don’t pay the NEM number until end of year, but I just paid it and it was another $500 of accumulated NEM charges.
The other strangeness for me is the recommendation to stay between 50 and 90 for daily use.
Studies of li-ion have shown 80-20 to be the optimal usage pattern for maximizing usable watts over the life of the battery.
So why isn't the utility managing the storage directly then? Aren't they best suited to do this???
Or is this article just saying that EV car batteries could?
They don't have a million EV batteries, purchased outside the scope of this program, sitting around idle and connected to the grid.
Their customers do.
From the abstract:-
> Participation rates fall below 10% if half of EV batteries at end-of-vehicle-life are used as stationary storage.
Half seems conservative to me. There are already lots of startups wanting your end-of-life EV battery.
But more capacity is better, and getting things online sooner is better. And in 2030 almost all the capacity is going to be in non-retired packs in their original cars.
Also, I'm not sure what components would wear out in an EV before the battery such that it would total the car out. If the EV batteries in totaled cars can be repurposed for grid use, then great, but I would expect them to get recycled and put back into cars unless strapping them to the grid is cheaper than recycling (seems maybe plausible?).
Way more important for battery life is the charging rate (again, LFP are more resilient there too). Which wouldn't be an issue for grid use.
The only complicating issue is calendar life of the battery when it is above 80%. Over time a battery loses capacity just because it exists, which I'm calling calendar life. The closer your battery is to 100% the calendar life decreases at a roughly quadratic curve (a battery at 80% has about 1/8 the calendar life loss of one at 100%). AKA you lose 8x more capacity per year at 100% than 80%. Temperature has a similar effect above room temperature or so.
So if your frequent charges keep the battery above 80%, that would reduce calendar life (increase capacity loss per year) on its own. LFP has far greater calendar life than lipo, but also cycle life too, so I think it's just as important to keep your EV at 80% or below, whenever convenient, regardless of chemistry, unless your usage will cause cycle life to end the battery usefulness before calendar life is significant; i.e. multiple full cycles per day. But also at multiple full cycles per day you probably won't spend much time above 80% even when charging to 100%.
Ah, to summarize, I'll repeat my simple advice: I think it's important to keep your EV at 80% or below, whenever convenient.
> I would expect them to get recycled and put back into cars
In that case, you'd also get something in return for not having used those cycles. It's a matter of choice then - do I rent out my battery during use, or do I sell it after 8 years.
> In that case, you'd also get something in return for not having used those cycles. It's a matter of choice then - do I rent out my battery during use, or do I sell it after 8 years.
Yeah, but which is more economical is the salient question.
In fact, the battery management system won't even let you fully charge or discharge the battery for exactly this reason. When it shows 100%, there will still be 1-2 kWh empty and the same for a zero percent charge.
For example, a Toyota Yaris use a tiny (0.7 kWh) lithium ion battery and it gets charged/discharged constantly while breaking/accelerating, but it still last a long time because the charge is kept at about 50%.
Sure, offer variable rates. Offer interruptabke service. But stop wanting V2G, nobody actually wants it.
I would like to use my car battery as a temporary home battery in the inevitable case of a grid outage. This opens the option to bring energy home from another location. Reduce or eliminates the need for a battery in a grid-tied house.
Am I crazy?
Edit: Granted that doesn't mean the energy company can use my car's battery at it's whim. I think compensation would be required and would actually make a lot of sense. It isn't like the electric company could build out a battery system for cheaper. It would need to be a higher compensation than to PV though. Batteries are more expensive and should be compensated as such.
V2L (vehicle to load) is a simpler form that lets you power 115/230V appliances directly from the vehicle. Quite a few EVs (Hyundai, Ford, etc) already support V2L.
FWIW, the F-150 Lightning car to home option only goes up to 40A, which isn't that much more.
Question is "how long?" and "how much?"
Lets take a 100 kWh battery which matches a Tesla Model S battery option and is a nice number for doing conversions from.
https://shrinkthatfootprint.com/average-household-electricit...
> The recent figures, as of 2021, show that the average annual electricity consumption for a U.S. residential utility customer is 10,632 kilowatthours (kWh). If you divide that by 12 months, the average monthly electricity consumption is 886 kWh per month. What about in a single day? That would be 10,715 KWh divided by 365, or 29 kWh. Then the average daily electricity consumption is 29 kWh.
So, hypothetically, 100 kWh would give you 3 and almost 4 days. This can be improved by unplugging things that consume more power. The other part with this is a "once that 100 kWh is drained, you're stuck stuck."
You're going to still need something between the mains power and the circuit breaker box. I'm also going to note I don't know what rate it can discharge.
You might also want to look at a system that is a dedicated whole house battery backup ( https://www.zdnet.com/home-and-office/energy/best-home-batte... )
The zdnet article links to a Lowes worksheet - https://www.lowes.com/pdf/portable_generator_wattage_chart.p...
And from that, look at the "this is what we want" and the question of "generator or battery" becomes interesting.
Then consider also, you can get a 10,000 watt generator (that does a cutover in event of a power outage in 7 seconds) for about $3000 which can provide 10 kW at 40 amps.
Those have the instant on design so that if the power is lost to the house you have a few seconds and its back up and running.
You may need additional equipment or an upgrade to existing equipment to do the power outage cut over. To do this (and not just support an outlet from the vehicle), it is necessary to remove the house from the grid for the duration - suddenly changing phases can damage equipment (e.g. when the power comes back on). Additionally, if you were still connected to the grid, it would mean that your batteries are trying to support the portion of the entire grid (which it will fail badly at).
This also depends on the equipment that you currently have. Not everyone has a battery backup Tesla power wall. If you are plugging the car into 120v or 240v outlets, that doesn't have the circuitry to support isolation of the house from the grid after a power outage and the wiring for the 120v or 240v outlet isn't heavy enough to support the current draw for the rest of the house even if it was isolated.
You may also decide that trying to do it from the car, while possible, is a bad idea. https://electrek.co/2021/02/23/tesla-voids-your-warranty-pow... and https://www.tesla.com/sites/default/files/downloads/tesla-ne...
> This New Vehicle Limited Warranty does not cover any vehicle damage or malfunction directly or indirectly caused by, due to or resulting from normal wear or deterioration, abuse, misuse, negligence, accident, improper maintenance, operation, storage or transport, including, but not limited to, any of the following:
> ...
> Using the vehicle as a stationary power source
The former is pretty straightforward. The latter would need a lot of electrical upgrades to the house. (I'd expect you'd need to do about the same thing that people do when they get solar, which is to replace the meter with something that can measure power flows in both directions, and is smart enough to disconnect the solar panels from upstream power when the power goes out, so you don't electrocute people trying to fix the power lines. If you don't have a local battery, that means basically turning the solar system off in a power failure.)
If you aren't planning on selling storage capacity to your local utility, maybe all you really need is an automatic shutoff switch to disconnect your house from the grid when the power goes out.
Either way you'd need some sort of power inverter to convert DC to AC. That could be built into the car, or it could be attached to the house.
Utilities really want V2G, so it's probably going to happen one way or another. It's probably less applicable to an individual homeowner, but commercial and other fleet operators are going to find this appealing at the right price.
For example: https://www.proterra.com/press-release/massachusetts-electri...
It's possible I suppose that cities and school districts could have busses that have more capacity than they strictly need, and so it makes sense to use any surplus capacity for grid storage (while maintaining a reasonable margin in case a bus has to make an unexpected trip because some other bus had a flat tire or something).
There are only idle for 2 or 3 hours during the day.
(Field trips can add another usage in the middle of the day as well)
Plenty of people are willing to drive 200 miles of Uber as a second job. V2G is a lot more appealing than that I think.
I haven't noticed any range loss ... yet. I know on mine the physical capacity is 14.4 kWh but it'll only let me use a band in the middle (?) of ~11 kWh (it eats 12 kWh charging and I'm assuming a 90% charging efficiency) (I also don't know if the chargepoint chargers report delivered or stored energy). This is all what I'm presuming to be enforcing no full charge/discharge cycles to lengthen the battery life.
I doubt the hourly price will ever truly be fair to individual car owners. Maybe we'll start to be asked whenever we plug in our phones to tip the owner of a car our electricity is coming from.
The aesthetic vibe of having an autonomous energy trading bot in my garage is attractive to me.
~1,500 cycles per $16k battery replacement. Shouldn't sell a full cycle for less than ~$15. Don't arbitrage a 1% point of battery life unless it yields at least $0.15. Might just set it at $0.20 per 1% for healthy margin/price-in hassle of battery replacement.
It's also not super clear how much wear small charge discharge cycles does on a normal battery if it's not in the bottom or top 20% of the battery.
If it's not fair to them, then they won't participate, and the market will adjust.
Indeed as this becomes more of an option I trust that car producers could look at engineering their batteries with this in mind.
The extra regulatory and technological stuff to make the Tesla power the neighbors house through the city grid is just overkill.
I also wouldn't want the battery level timed around the grid vs my own transportation needs. What if there is suddenly a heavy demand on the grid, and now I can't take my sick family member to the hospital, because the charge was sold to the grid?
Battery swapping is already a thing. In China. Nio[1] sells luxury cars and there are lots of more utilitarian vehicles that use battswap, but get no press outside China.
In the west, Ample[2] is working with manufacturers to modularize batteries and make them swappable between vehicle brands, so a "gas station" business/industry model will work.
Edit: I believe that EV manufacturers that don't offer battswap will confine themselves to the luxury niche of the market. The mass market wants low sticker prices on its vehicles.
Very interesting what happens to car depreciation when decoupled from any particular battery pack.
Come to think of it - a harder part is how super local the grid is and energy pricing should become. In my somewhat affluent neighborhood in high summer the voltage rises too high and the supply of solar falls. And tragedy of the commons - we are still installing solar because it’s massively incentivized (2 years before investment returns itself). To solve this with EVs requires very granular prices. There might be clouds 50 km away. But again, those are software solvable issues. (I’m not holding my breath. It’s like IoT-superplus.)
I envision a future where individual appliances (including EVs) can opt in to spot pricing for the electricity they consume (or produce). That would naturally incentivize charging during off-peak hours and discharging during peak hours, all without requiring any government incentives or coercion. It could also be useful for other major appliances which could benefit from the lower prices afforded by load shifting, such as hot water heaters.
I remember when high speed internet was coming into being and there were a lot of pundits talking about how high speed bandwidth would be sold as a commodity on the NYSE. If someone needed say an hour of high bandwidth for a video conference, they could do what you're saying, buy an hour of high speed access. Of course, high speed internet eventually became so cheap and so readily available, those ideas faded pretty fast.
I might be remembering this wrong, but wasn't Enron doing what you're talking about?
When 1,000 devices jump on the grid the moment electricity hits $0.01/kWh, the demand spike will cause more generators to come back on line and increase the price back to $0.05/kWh -- thus causing the 1,000 devices to drop-off the grid.
Rinse, lather, repeat.
How do you compensate for the potential grid instability?
Assuming instability does actually become a problem though, that sounds like a very straightforward technical problem with many possible solutions. Just off the top of my head, the simplest market-based solution would likely be futures trading. If all these appliances reserve their electricity usage 10 seconds in advance, then sellers can know exactly how much demand there'll be and adjust their production accordingly, maybe even bidding on that capacity so they know in advance exactly how much they'll need to produce. I imagine the high-frequency trading industry probably has tons of experience with this sort of thing.