That's quite a complex equation to balance, @agentgeorge.

Let's try and separate out the different points.

On the face of it, a year's free charging is quite a draw; based on my historical driving, that would save me about £1,400 for the year. However, it's not quite that simple. I'm aware you have solar panels and I have to assume you have a battery too. As such, any time you're charging the car during a sunny day, anything you generate will go into the car before the grid. That's great for most of us but in this particular scenario that's free energy you're not taking from the grid and free energy you're generating that isn't earning you 15p/kWh. You may well be able to align the charging cycle with night-time only in which case fuel-wise you're saving a good chunk but not being able to charge during the day without losing money does somewhat reduce the value of the offer.

Next, the range. The BYD Dolphin with a 60kWh battery has, according to Which, a tested range of about 220 miles. That sounds like a lot but if you stick with the recommendations for looking after your battery that means not generally charging it above 80% or letting it discharge below 20% which leaves you with a practical working range of slightly over 130 miles. My car tested at about 210 miles range (working range 126), so is very much comparable and I can say that that leaves me with plenty for the usual running around and a safety buffer to boot, but not all that much extra that I'd want to sacrifice back to the grid - bear in mind that you're not being paid for the energy exported back to the grid since you're instead being given that free charging.

My car with a bit of judicious use of home automation logic combined with the solar PV produced is, by my sums, saving me about £850 per year on my automotive fuel bill, so the net benefit of that free charging deal is not £1,400 so much as £550 per year.

Let's also factor in that this V2G scheme is via a tariff add-on (Power Pack) that is not compatible with their Tracker, Agile or Intelligent Octopus tariffs - exactly the tariffs that can provide you with a lot of savings in other ways. It's also the case that you have to commit to (for 20 days a month) keeping the car plugged in for 12 hours a day. If, like me, you need to clear off for work at around 7am - ish then that means not using your car in the evening before after about 7pm, and that's exactly when quite a bit of our running around happens.

The EV rental scheme they have doesn't have the BYD Dolphin yet so I can't see the typical monthly cost, but do bear in mind that it is a rental - you don't own the car at the end of it all. However, £300 seems to be the practical starting point to work with (around £380 for a few extra bells and whistles), meaning £3,600 per year. Under normal circumstances I'd suggest it's more cost effective to buy a car outright and then run it into the ground but EV technology is evolving rapidly enough that you may feel it's worth a small cost penalty specifically to avoid locking yourself into one car and instead have the flexibility to chop in and get something with fancy new tech in a couple of years. Certainly not a clear-cut choice here.

V2G is still not available yet, with you instead needing to join a waiting list. The only cars compatible with Octopus' V2G scheme are currently relatively short range models and, whilst I am very much interested in V2G in general I personally think it'd only be practical for me with a car with 300+ miles range. When you add in all the other restrictions and caveats I've highlighted, it's not currently an attractive proposition for me at all. However, it's not about me, it's about you; I'd be interested what you think.

@majordennisbloodnok 

your summary is along same

lines as I was thinking, pcp on a car is for those who can afford it and dont want to own a car but want a new one every few years.

i used to be like that, but since retiring several years ago, Ive been slowly adopting green tech

Heat Pump, UFH, Solar PV, as much as roof can hold, with battery and insulating every wall, floor and roof space.

i have a Pug 308, real world miles 150, depends on weather.

Does me as a local run around. As you spotted, the V2G Dolphin is on a wait list, probably being rolled out in the autumn.

There are a couple of V2G vehicles already, think Hyundai 9 and Porsche Taycan but if you’re not being paid to export to grid, theres not much incentive to sign up.

i was looking at Off Grid possibilities, my current PV system needs a big upgrade to achieve that, so getting an EV that charges at 7p kWh and supports the house during the day would be a better option than supporting the grid.

early adopters dont get the best equipment, first gen leaf could do 70 miles, the latest they're hoping for over 200.

i also read about new Sodium batteries, abundant supply in sea water unlike lithium, used as huge storage farms to store excess power, unlike current system on a windy day, turbine owners are paid an obscene amount of money to not generate; but thats another topic

@agentgeorge, I was also more interested in using a car’s V2G capabilities as an extension to the home battery than as an exporter to grid. That’s why I went for a VW. Still not quite a mature enough scheme yet, though.

For me the exciting prospect is v2g for our 'second' car.  Currently a petrol fiesta, it spends most of the time on the driveway rusting away and doing nothing useful, because we prefer to drive our e-niro.  If we could replace it by a 10 year old high mileage 30/40kWh leaf, available for 5k, which most of the time is used as a home battery it could really earn it's keep.

My hunch is that enough people have second cars sitting on the drive for most of the time for this to make a real dent in our need for local network expansion.  However if it relies solely on new cars then it won't cut it.

@jamespa 

I have a friends EV parked on my drive for the summer as he likes to drive his MX5 when its sunny. If I could hook that up to charge at 7p and export at 15p, I could make £3.50 a day. Is it worth that amount?

Posted by: @agentgeorge

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If I could hook that up to charge at 7p and export at 15p, I could make £3.50 a day. Is it worth that amount?

As has been discussed on other threads, trying to justify a purchase based on the difference between import and export tariffs that may well not exist in a year’s time is a bad idea. Playing the differentials is better seen as a bit of beneficial opportunism.

Thinking about it financially, the battery - whether a home battery or a V2G car - will serve you better if it’s filled for free or very cheaply and then used to provide power for appliances that must be run during expensive times. Buying a kWh for 7p and selling for 15 will only make you 8p. That same kWh bought at 7p and used to power the ASHP during the expensive period will save you far more, and if the heat pump needs to run it’s a kWh that still needed to be consumed.

Id also add to this thread that V2G (Vehicle to Grid) is not necessarily the same as V2H (Vehicle to Home).  Allowing an energy provider to offtake your car charge to support the grid, wont necessarily allow you to use the car battery to run your ASHP or other home appliances.

V2X (Vehicle to anything) is the real consumer champion, Im assuming thats several tech generations away, not because it cant be done, but because the companies releasing the tech need to see how they can gain the most benefit.  Expect standards wars, government intervention and finally consumer pressure to get the mass market to V2X.

I pray Im wrong.

Posted by: @scalextrix

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V2X (Vehicle to anything) is the real consumer champion

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I agree, but a word of caution. V2X is also sometimes used in a different context making for quite a confusion. My VW ID3 supports V2X in the sense that it as a vehicle talks to other vehicles (the X meaning any other vehicles) to share information about speed, position, traffic incidents and so forth. This is a far cry, of course, from V2X in the sense of bidirectional charging. If you’re researching V2X compatibility, double and triple check which V2X the document is referring to.

General comment on battery care... I guess if ev is on a contract for say 3 or 4 years then charging to 100% and discharging to maximise imports/exports is less of an issue. The degradation will mostly land on the next owner?

Not ideal but if that's how contracts are designed then they are likely to be used.