Undeniably doable, but might be less worthwhile than it first seems.

Consider as an example, a battery that provides 25 kwh on discharge. There will be small but real losses in the charger, in the inverter, and in the battery itself. So to provide 25 kwh of electricity output might require about 30 KWH of input.

Then consider the cost of the battery and the depreciation thereof. If the battery lasts for 2,000 cycles, and costs £10,000 then each cycle costs about £5, IN ADDITION to the energy cost of charging.

So if the cheap electricity to charge the battery costs 10 pence a unit, it will cost £3 per charge, plus another £5 for battery depreciation, or £8 in total.

The 25kwh produced on discharge will therefore have cost in total about £8. That is about 32 pence a unit. Slightly more expensive than the capped domestic price of about 30 pence a unit.

Wot 'e said.

At some point, on some TOU tariffs, it might be worthwhile, but the maths needs to be done properly or as broadgage says there will be unhappy people when time comes to buy a new battery earlier than expected. To be fair, it is worth noting that battery life is defined arbitrarily and it doesn't stop working at all beyond the nominal cycles, but you will be beyond warranty and capacity will have fallen, which might well be a big deal for the primary use of the car. Or not if you only drive round the block anyway.

For commercial / utility scales this arbitrage with batteries it is already being done as part of the "revenue stack", because the price differential between demand peak and trough is somewhat greater and they're not paying to wrap their battery in a car.

Also don't forget that it turns your site into a generator so G98 / G99 required, and not all car chargers can do it.

broadgage said:

Undeniably doable, but might be less worthwhile than it first seems.

Not just doable, but done: https://octopusev.com/powerloop

When energy companies offer you preferential rates for electricity, in return for the use of your vehicle batteries (and perhaps when it gets going fully, solar "self-consumption" batteries), it is likely to be the best option (perhaps you will pay through the nose for energy unless you have this flexibility for your energy vendor).

broadgage said:

Undeniably doable, but might be less worthwhile than it first seems.

Not just doable, but done: https://octopusev.com/powerloop

When energy companies offer you preferential rates for electricity, in return for the use of your vehicle batteries (and perhaps when it gets going fully, solar "self-consumption" batteries), it is likely to be the best option (perhaps you will pay through the nose for energy unless you have this flexibility for your energy vendor).