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Comment by neallindsay | Hacker News Reader

There's lots of talk about grid-scale batteries to shift cheap electricity from solar panels into the night time. But batteries at the periphery can also help a lot because they can just stop charging (like the example in this article) or even feed energy back into the grid. Electric cars mostly don't have the circuitry to do this yet, but they're becoming a huge resource that will be tappable this way. Most of them are massively over-provisioned for the way that they're used 350 days out of the year.

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Green Mountain Power does exactly this in Vermont: they have a program that'll install a pair of powerwall batteries at customer homes and charge them off peak to draw on them on peak, particularly to avoid GMP having to buy peak-rate power from their upstream suppliers. In return, they leave the batteries charges when the weather is turning bad and the customer has battery backup.

The deal is structured as a 10 year lease, and the total cost is vastly less than that of owning the batteries outright. Their installation allowance is pretty good too; it didn't cover splitting our panel, but it covered everything else.

Not affiliated other than being a very happy GMP customer.

You say they leave the batteries charged when the power is turning bad. Do you have a benefit of hosting the batteries at other times? For instance if the power goes out when the weather isn’t bad, do you typically have enough charge to make it through the outage?

I’m also curious if your neighbors benefit from your battery during outages.

De jure, I think they're pretty free to do with them what they want. De facto they leave the batteries pretty fully charged most of the time.

AIUI, they'd have to have a disconnect somewhere upstream of us to let us back feed the grid during an outage, otherwise they couldn't safely work on the lines. And they'd need a way to enable and disable back feeding remotely[0] to allow them to work on anything between that hypothetical disconnect and us.

At the moment, none of that exists, so only we benefit from the powerwalls. It's also 34kwh in the pair of batteries. That wouldn't add up to too many household-days if you started adding households. You'd have to do some fancy switching to not overwhelm the relatively few powerwalls in an outage.

For context, based on our usage, we're at about three days of backup just for us [1]. It doesn't take much imagination to come up with a scenario where that happens where we are. We are the very last pole.

[0] Which in turn requires connectivity. The cell network here is sparse, to put it mildly. We just got fiber, but that's hanging on the same poles as the power. The fail-safe mode for no grid and no connectivity is to not backfeed, but at that point, you're back where you are today.

[1] It's the fridge, mostly.

You don't need internet for everything... by definition these systems are connected to the grid by wires which can transmit a limited signal. Utilities in countries such as NZ have managed load for decades by turning hot water heaters in customers' homes off and on remotely with ripple control units which transmit a signal over the power line itself. [0]

[0] https://en.wikipedia.org/wiki/Zellweger_off-peak

This is correct, an added benefit is if the power poles are actually down then the communication over the powerlines would be down, but that’s fine as power couldn’t be sent over the lines anyway in that case. What I wonder about/have concerns in regards to, is as someone else mentioned the relays required to turn on and off backfeeding in terms of electrical Utility workers having to de-energize a line to perform work. I’m not too sure that these workers can entrust their lives to the reliability of various (multiple) relays to not sporadically switch back on once the line has been confirmed as de-energized (in other words depending on the relay not to malfunction and re-energized while the workers are working upon the line )

I assume there will be some types of tools to monitor / alarm the workers for exactly this scenario (ie something they can attach to the line while it is being worked on and if it becomes re-energized an alarm will sound).

Generally grid backfeed capability for these systems is predicated on the presence of a stable voltage and frequency already on the grid - this is both a safety measure and a practical necessity, as the inverter needs to synchronize with the grid frequency.

Just to add the terms: a "grid following" matches the grid's voltage/frequency, so it only works when connected to the grid. A "grid forming" system can set its voltage/frequency independently and can only work off-grid

It sounds like mauvehaus is talking about a hybrid system that has both grid following and grid forming capabilities: switching to grid-forming as it disconnects. But that means that you can't power your neighbors.

I wonder why it is that real world systems don't use a GPS receiver to obtain a 1 Hz signal that's synchronized to the GPS clock and then generate a local 50/60 Hz clock for grid synchronization.

I'm just an EE with no experience in real power systems, so this may be absurd to someone who knows how this stuff works.

I didn't take power systems either (EE that went CE), but even if your clock was accurate and the system was tuned wouldn't you still likely be out of phase? I don't remember enough about the whys (like, does the type of load modify the frequency? gone down the memory hole) but I remember a guest lecturer mentioning that the actual frequency frequently had small deviations from nominal, too

Yeah that's what the synchronization is for - the precise frequency doesn't matter except for consumer devices that use it as a clock signal. If the hot line is at 120V and you're a quarter cycle out of phase at 0V, all of that energy is just going to flow directly to your circuit and destroy something. Since the frequency represents the spinning of large turbines, a power plant going online out of phase is essentially slamming their turbines into a massive external force (things go boom).

If you use GPS-based synchronization you have a reference of when zero crossings should occur. This does not mean that you have to output exactly that waveform.

Once you have a reference you can use a control algorithm. like a PID, to adjust the phase of the grid that you are generating locally.

If you sense that the grid is running out of phase from what your GPS clock says is the true reference you can increase/decrease your power output a bit to increase/decrease its frequency and catch up with the phase error.

It would be analogous to a type 2 PLL. The 1 Hz GPS clock would be the reference clock, the 60 Hz grid would be the "PLL output" and the VCO would be the power turbine, or AC inverter.

Ok, potentially stupid question, but if you're already using the grid as a control signal what do you need the external clock for?

From the comment I replied to:

> Generally grid backfeed capability for these systems is predicated on the presence of a stable voltage and frequency already on the grid.

You are using the reference clock to know precisely how misaligned the grid is and you use the reference to make small corrections to the generator power or inverter phase to restore phase alignment.

If you have an external stable reference clock (GPS) you know what the grid *phase* should be and it should be easier for network of multiple small inverters to keep the grid stable and to bring it up by themselves if there's a large blackout.

Bless, thank you for helping me take that one full circle.

It doesn't help under normal operating conditions.

It takes roughly 16ms at the speed of light to cross the US. 16ms is also coincidentally one entire cycle at 60Hz. So, who should sync to GPS and at what phase?

In addition, when the grid begins to get overdrawn, the phase begins to slide due to the physical nature of generators.

Global sync doesn't really matter; local sync is what's important.

Back in the 90s, I interacted with a home intercom system that ran purely on the electric wires. Just plug in the devices into any electric wall sockets, and they just worked. Voice wasn't too bad either.

Question: when an actual power outage happens, does the powerwall backup take over immediately without loss of power to the household? Or if not how long does it take to switch the grid interlock? Just wondering if this would be suitable as a UPS for my computers.

It's entirely transparent. The app will notify after the power has been off for some amount of time to avoid nuisance notifications for flickers or brief outages.

I wonder how the lease is funded. Usually these sorts of incentive programs have a big catch.

That happened a lot with solar panel leases, so now people have solar panels on their roofs that are effectively owned by a bankruptcy courts, which can make it hard to sell the house. (There's no one to contact to transfer the lease to the new owner.) Since GMP is a power company, that's probably less of a risk.

Anyway, the other features you mentioned are pretty standard. Enphase does all those things, and I'm pretty sure powerwalls, lg systems, generac, etc do too.

This page has info on the GMP program:

https://greenmountainpower.com/news/gmps-request-to-expand-c...

So, $55 / month for a lease of two powerwalls (26KWh total) which is $6600 over 10 years. They'll also provide a $10,500 incentive if you purchase your own battery. A powerwall costs $9300, so it'd be $8100 out of pocket to buy them instead of leasing.

(The above doesn't include installation.)

I wonder what happens at the end of the lease. Either way, the lease looks like a better deal, even if you assume a zero percent interest rate.

Utilities can have huge capital budgets, and programs like this are weighed against the cost of building new power plants or contracting with external power sources. It's money that was already going to be spent - programs like this redirect funds.

> Electric cars mostly don't have the circuitry to do this yet

Electric cars do have the circuitry to do this. It's built into the CCS protocol which nearly every EV speaks (US and EU).

And it's not hard to imagine how this would work. Two big connectors on EVs can ultimately be hooked pretty much directly to the battery. When you plug in, you'll hear a giant "cachunck" which is the relay switching to DC charging.

If you want to turn that into a vehicle providing power, the action is exactly the same, "cachunk" the relay which completes the circuit and have the charging station convert that DC power to AC.

That's where the actual equipment gap exists. AFAIK, it's basically only ford that's producing a V2H charger. Enphase has one announced since last year, but I've not really seen anything about it since the announcement.

Tesla has a V2H/V2G (Powershare is the name Tesla uses) available for Cybertruck owners included as part of the vehicle purchase. I am still waiting on mine, despite receiving my Cybertruck almost 6 months ago.

I also have the Ford equipment from when I got my Lightning, however finding a competent installer has been impossible. Right now it's collecting spiders in the corner of my garage.

Do you have anyone that does home battery installations? It should be pretty much the exact same process to install one of these. It may be somewhat new tech, but ultimately it should look identical to battery controller install.

Don’t forget about airplanes, you can fly in competent installers, some may enjoy the trip :)

A Lightning and a CyberTruck? Have either touched dirt? :)

The Lightning has plenty of times since I am confident I could get it repaired or replaced easily. The Cybertruck... not so much.

Good! I had to ask. I’ve seen multiple Cybertrucks driving around my neighborhood and I’m pretty certain none of them will ever touch dirt. I hope you enjoy both vehicles!

In Switzerland it's also forbidden (as of now) to even think using your EV as external battery. The energy companies are fighting tooth and nail against people becoming independent from the(ir) grid.

Is it in the CCS protocol? My understanding was that the F150 used a custom extension in order to do its thing where it will power your house. And even they don't feed back into the grid, which would require synchronizing the A/C.

If there's already a protocol built into CCS for vehicle-to-grid then that's great news, but manufacturers would still need to enable it.

There have been some test deployments of vehicle-to-grid in the US from Leafs since they use CHAdeMO.

> Is it in the CCS protocol?

Yup [1]. It was an early proposal before CCS was ratified and has been there since the start.

> My understanding was that the F150 used a custom extension in order to do its thing where it will power your house. And even they don't feed back into the grid, which would require synchronizing the A/C.

Both the F150 and CT have onboard DC->AC inverters. This, IMO, is a bad move. It makes way more sense for the inverter to be a part of the house. However, the onboard inverter does make it easier to integrate with generator switches in panels.

If I were to guess, the reason we've not seen a charger/generator combo has more to do with the complexity of battery voltage platforms. Unfortunately, CCS does not specify pack voltage which means any inverter would need to handle anywhere from 600->900V from the car.

[1] https://www.greencarcongress.com/2009/09/emobility-harmonize...

> Both the F150 and CT have onboard DC->AC inverters. This, IMO, is a bad move. It makes way more sense for the inverter to be a part of the house. However, the onboard inverter does make it easier to integrate with generator switches in panels.

Having the inverter in the truck makes it useful for construction sites where you need electrical equipment and utility power isn't connected for whatever reason (a good one is construction hasn't gotten there yet; but also sometimes 240v tools are needed and there's no convenient access to 240v), and makes the truck a drop in replacement for a portable generator that people may already have.

Agreed, I should be clear that I think it's a bad idea for a general V2H solution.

The problem with both of these is their capacity will be determined by the manufacturer. CT has a max output of like 3kW, which is unfortunately quiet low.

These batteries on pretty much any EV sold (including phevs) should be capable of spitting out 15->50kW.

I think it's appealing to nerds to believe that a long-tail disaggregated phenomenon like EV V2G is going to save the grid, but the apparent truth is that the grid will be saved by central planning and top-down command and control. We see this in California. We have a million EVs registered in the state, but our grid-scale, CPUC-regulated battery stations are still larger in terms of energy storage, and unlike the EV fleet the availability and responsiveness of battery energy storage stations is assured.

Load shedding like that in the article is a vanilla feature of electric grids everywhere. Large consumers get discounted power in exchange for agreeing to disconnect during grid emergencies. Because the number of such customers is small, that feature is easy to regulate and you can ignore the game theoretic shenanigans that would emerge from widespread V2G with millions of individual participants.

Tesla will come to the utility and say we can offer you 3000 MW of demand response in any granularity you want for $x/hr.

$x is usually not very big since the modus operandi for the bulk electric system in North America has been everyone can use as much power as they want whenever they want, so we have had lots of supply.

But a couple of times per year $x could be thousands of dollars per MW per hour, for a few hours. So not worth the effort really.

Maybe Tesla will offer the demand response more geographically so distribution utilities can also use it for peak shaving on their substations. But that is pretty brave area to be operating in for a utility, depending on Tesla to avoid overloading transformers or risk a localized black out.

There would have to be a serious penalty for bidding in the demand response but then not performing as well.

I agree it does seem far fetched at this time.

Edit: price signals to consumers is probably a better mechanism

> appealing to nerds to believe that a long-tail disaggregated phenomenon like EV V2G is going to save the grid, but the apparent truth is that the grid will be saved by central planning and top-down command and control.

I think this sentiment applies to a lot of facets of the energy transition/preventing climate collapse - perhaps sadly?

A lot of the cooler distributed solutions and demand-side solutions could have been our saviors had we started on them in earnest 10-15 years ago. They should still be pursued as part of a robust and resilient system (everything from re-insulating homes to V2G to cutting out dairy and meat from diets to dispatchable home heating/cooling-appliances etc etc) but the truth is that we are spiraling towards climate collapse and those sorts of solutions are simply put more difficult to implement and maintain, especially because they often involve massive social buy in; at the same time, those solutions don’t tend to address the source energy question in any meaningful way (besides rooftop PV which is not enough even for low energy homes in many climates), so supply-side solutions will always still be needed, and like you said, there are economies of scale in both thermodynamic/physics efficiencies and in management and planning. It would be awesome if everyone stopped eating steak, but the realist in me knows that expecting that to happen at a scale which moves the needle just does not seem realistic.

It’s sad to me in that the “distributed” solutions tend to actually address root causes of climate catastrophe - addiction to energy consumption, “capitalism” writ large, being good denizens of the planet, etc etc in one way or another - and would entail a real improvement to how we understand the fabric of society and modern civilization (I’m speaking broadly here of course, but I think it holds water), whereas the centralized solutions feel in some sense like bandaids that obfuscate our collective responsibility and engagement with the issue (besides tax dollars and utility rates going towards the solutions I guess), but at the timescale of the crisis we are dealing with the size of that lever and its effectiveness is kind of unarguable I think.

Build big solar and wind farms, lots of batteries, start using cleaner steel and cement manufacturing processes, hope that super deep geothermal or micro-reactors progress, hope that we find a better way to sequester carbon coming from either direct air capture or post-combustion carbon capture.

Everything else is just (important) gravy. And I say this as someone mostly focused on the demand side, not supply side! (I’m a building scientist)

California is a bad example of "working power grids".

Thanks to decades of graft, PG&E keeps blowing up / burning down neighborhoods / cities, and then passes the liability cost to consumers.

At this point, we're paying $0.40 / kWh for grid power. National average is $0.08. Our solar + battery system is saving us something like $600 / month for a small, energy efficient house + one small, energy efficient EV.

With the new rates, there's barely any financial reason to connect to the grid at all. You have to get solar + battery anyway, and getting a backup propane generator to keep the batteries from running empty is only an additional $10-20K.

At that point, your house would be off-grid capable. Assuming a 10 year depreciation cycle on the generator, that's an additional $166 / month over the equipment's lifespan.

Finally, assuming people move to battery + solar to avoid paying $500-600 per month ($60K over ten years, which is more than battery + solar cost, so everyone should do that right now), they'll have to raise the rates so that people that are almost never importing power are still paying enough to cover liability + grid maintenance.

$166 / month / house isn't going to cover that. PG&E's screwed.

Personally, I want to buy a direct air capture device that I can plug into my house. Whenever the batteries charge above about 80%, I want it to convert all surplus electricity into little solid carbon bricks, and dump the "waste" air (with low CO2 content) into my house. That + propane generator + close my PG&E account seems ideal.

From a quick peak it looks like most of the gas to solid processes require a non-trivial amount of heat (ignoring turning it into dry ice cause it'd just boil away anyway), but I suppose your capture can be separated from your condensation and cooled separately.

You ever look at what the throughout might be? I was just curious if a homelab setup of what you described was possible but that was as far as I got

> At this point, we're paying $0.40 / kWh for grid power. National average is $0.08.

It doesn't help to exaggerate, that only undermines whatever legitimate point is buried in here. California weighted residential cost was 33¢ according to latest EIA data and the national average was 17¢.

> You have to get solar + battery anyway

Since more than 99% of California homes lack such a system, it is obviously not necessary to own one.

Even lower hanging fruit would be increasing the dispatchability of demand in homes. Simply allowing heating and cooling to be dispatched would be very helpful. In the past this was done with bespoke add-ons to furnaces and AC compressors, but now it's done with smart thermostats.

Dispatched versus random dither are similar;

For most smart thermostats, one of the lesser known quality improvements is the 5 minute + dither time for startup. This is designed for compressor health - but prevents repeat cascading brownouts - where programmable thermostats or manual thermostats would have either a strict 5 minute wait time or none at all.

Other features like time of use, humidity correction, and fan circulation also drastically reduce energy usage.

Our thermostat seems to apply the delay even when you manually turn it on.

It drives me nuts. (After a power failure or during scheduled transitions make sense; after I push the button: not so much.)

ISTR they did this somewhere (getting a discount on power in return for letting them decrease your cooling remotely at peak times) and the political right threw a national hissyfit.

I signed up for this in Illinois and never heard a single peep of complaint about it (nor did I ever notice it when it kicked in.)

If you don't have a smart thermostat, check whoever your utility is for discounts. I got a 50% discount buying it through them.

My utility keeps sending me google thermostats for free despite having ecobee. I keep giving them away but they keep sending them!

Heating and cooling would be massive. Another one is dishwashers (eh) but also laundry machines (washers and dryers/hot water heaters). Pushing those to random overnight spacing or preferably midday can help at least a bit.

On-demand charging is very much happening today. All chargers communicate the available charging current with the vehicle and some can adjust it dynamically.

As for control, there are proprietary and OSS solutions (shout out to https://evcc.io/en/) that allow you to control the charging process based on price, grid load, local PV generation, etc.

I see the basic version of this already with the Tesla vehicles where if you plug in another appliance on the same breaker the car will decrease its draw to prevent triggering the breaker.

> where if you plug in another appliance on the same breaker the car will decrease its draw to prevent triggering the breaker.

That's alarming. There's no way the car can know that there's another appliance on the same breaker. The only way it can know it should decrease its power draw, is by detecting that the voltage decreased on the circuit, but that voltage decrease will only be noticeable if the wiring is undersized for the load (in fact, that feature is probably designed to protect against overheating undersized wiring on the circuit feeding the car). That circuit is probably severely overloaded, which can be a fire risk.

This feature doesn't exist. The Tesla home charger can share current with other Tesla chargers on the same branch. It can't share current with an electric water heater or some other non-Tesla load

I think the OP was just confusing a feature used by someone with a Tesla from a Tesla specific feature.

They might be using one of these: https://www.chargedfuture.com/240v-outlet-smart-splitter/

There’s also smart breaker boxes that again have nothing to do with Tesla specifically. The breaker box will preferentially shed EV charging first when someone would otherwise trip their whole homes’s connection to the grid. It’s not a perfect solution, but sometimes your local utility doesn’t want to upgrade your connection to the grid because their substation is fully provisioned or whatnot.

I wish it were standard practice to have some kind of house battery (what Tesla calls "Powerwall") for new construction homes. They could smooth out peak usage in this exact way, in addition to making individual homes more resilient to occasional power outages.

It might happen! There's a fair bit of active research into repurposing batteries from cars into such a purpose or similar.

This both extends the usefulness of the manufactured good (the battery) while also hopefully lowering the upfront costs of new electric cars.

IMO this isn't the direction we're going. I'd bet that in 20 years, there will be some form of grid-scale specific battery that is 2-3x cheaper than lithium iron (per joule), but with much worse energy density. Many of the batteries of this type are unsuitable for home installation (because they get more efficient with scale). Some of the potential options for this are things like iron sulfur batteries which require pretty high temps, or some designs for batteries that basically involve physical pumps to pump liquid anodes and cathodes around.

> some designs for batteries that basically involve physical pumps to pump liquid anodes and cathodes around

Yeah in addition to flow batteries there are also grid scale thermal batteries, though these are targeted more towards long duration energy storage: run electricity through a large carbon block in a shipping container form factor to heat it up, then use infrared photovoltaics to convert back to electricity when desired.

I'd be interested in learning more about this carbon block battery that you're describing.

I'm also curious how it compares in cost effectiveness to this battery that's based on sand.

https://tambaynews.blogspot.com/2022/07/worlds-first-commerc...

Antora is one example: https://antoraenergy.com/

In addition to a few hundred mil in funding, they have support from NREL/DoE, eg https://www.nrel.gov/news/features/2024/how-nrel-helps-start... I also was at a conference recently that had some cool feasibility studies done by people at NREL about using TPV for LDTES with Antora product specs used for boundary conditions, but I don’t think that’s published yet.

I’ve also seen FourthPower mentioned a few times but I don’t know much about them or how feasible their tech actually is.

https://gofourth.com/our-technology/

Energy storage is not my area of expertise (but very much adjacent to it).

I think I'd prefer having new large-ish developments (20+ homes?) install a single house-sized building filled with batteries so individual homeowners don't have to sacrifice space or deal with maintenance, replacement, insurance, etc.

What if Your Town Doubled as a Private Power Grid? Around the country, developers are building microgrids — energy-resilient communities that act as their own energy source.

https://www.nytimes.com/2023/08/07/realestate/microgrid-sola...

> ...

> The couple liked that each house came with a three-kilowatt rooftop solar system, which would reduce their carbon footprint and cut their utility bill by a third. But as they toured the 31-home community, they discovered that they were looking at North Carolina’s first residential “microgrid” development.

> A microgrid is a network of buildings that essentially acts as a miniature power grid. It can operate outside of the larger municipal electrical system by ensuring backup power for the entire development, which can be produced by a solar array system and stored in a battery.

> ...

> At Heron’s Nest, the 62-kilowatt solar system and 255-kilowatt-hour battery are maintained by the local utility, Brunswick Electric Membership Corporation. Homeowners get a monthly energy credit on their utility bills by signing an interconnection agreement with the utility, which controls their hot-water heaters and thermostats when there’s high power demand. If the local power grid is stressed and the utility believes a power outage is necessary, residents here will be able to keep their lights on.

It depends on the situation. That approach doesn’t seem great for rural areas where outages are most likely.

This is the ideal. I think a happy medium -- which some companies are already working on -- is adding batteries to appliances. This allows them to charge when electricity is cheaper or provided locally (i.e. solar) and act as a buffer for outages.

So you want to make one of the most unaffordable assets a person can buy even more unaffordable by mandating a big extra investment to prop up underinvested infrastructure?

Perhaps for building blocks (if US ever densifies away from single family homes) would make sense.

Its a drop in the bucket relatively speaking, more like insulation in terms of upfront cost to provide a benefit and reduce long term costs.

It's... really not if you tried to actually build it.

The building materials aren't what's causing housing to be unaffordable. It's single family zoning and land speculation. The best thing to do to lower housing costs is to drastically reduce single family zoning (some cities have like 90% land area zoned for detached single family houses only!) to allow for infill development of SFHs into denser housing, and to implement an unimproved land value tax to discourage profiteering on land.

Sure, but slapping a 20-30.000$ on top doesn't help at all.

There are a number of industries that also do this where they'll be voluntarily shut off or pulled back during times where the grid nears brownout/blackout because their processes are interruptible with minimal cost which for battery charging stations is pretty true unless they're entire stock is at a very low charge.

I wouldn't want to participate during emergencies, though.

If a hurricane or a winter storm is coming, I want my car at 100% in case I need to evacuate, drive around to get food, etc. On top of that, who knows when I'll be able to charge the car again.

If we rely on cars to help stabilize the grid, it's not ideal that people will opt out just when it's needed the most.

Wouldn't you want to reduce the number of charge/discharge cycles on your EV battery? Using it for household needs outside of an emergency seems wasteful.

A modern battery far outlives the rest of the vehicle when you look at the charging cycles. So you can afford to use some of it for home electricity storage. AFAIK some cells types easily last 3,000 cycles at >80% capacity. Assume 400km/charge you’d be looking at 1.2mil kilometers of driving just based on the battery.

Also, there is a a natural limit to how much you’re using, considering you also want to use your vehicle for driving as well.

Not every charge/discharge wears on the battery the same. Staying at 0% or 100% is worse than staying around the middle. Charging and discharging extremely quickly wears more than slow charges/discharges. And high temperatures are bad for battery health in general.

Electric car batteries are tuned much more conservatively than phone batteries and are massively over-provisioned because US consumers are nervous about exactly the thing you're talking about. That's not too surprising because to a large degree the car IS the battery, but battery wear is generally very well mitigated (with the exception of the Nissan Leaf).

Early Nissan Leafs. At this point, the newer used ones include battery health management, and should be similar to other used EVs.

Note that getting an old one with a dead battery makes even less sense than you'd guess: It'll burn out any replacement battery just as fast, assuming you can actually get one.

If I was able to use my EV as an external battery for my home, I could potentially save ~$100 per month on my power bill, and that would represent <1/2 additional charge cycle per day. I'm pretty sure that would be worth it. This is going to depend on the power rates in ones particular area though.

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