How much will I save when I go EV?

Not in this case where the op is facing large repair costs for his current car.

You must be driving a 3.0L diesel if you're just getting an average of 35mpg. All my cars were & are diesel for longer than I care to remember and only a Toyota Landcruiser jeep I had fell below your average mileage - 45 to 55 mpg is what you should expect on long motorway journeys if you cruise at under 70 miles per hour.

Regarding saving money if you go electric - rest assured that will not happen. The only way you could possibly save money is if someone gifted you an electric car and took away your current ICE car without any money changing hands.

Say the value of you current car is €9,000 and repairs would cost €2,000 to make it roadworthy and pass NCT etc. Diesel costs + repairs = €5,6550

Buy an electric car for say €40,000 - the minute you drive out of the garage forecourt the value of your car will drop at least 10% - that €4,000 of you finest euros. That saving alone would pay for your diesel for 14 months! and that depreciation will continue - the percentage annual drop will depend on the market, the economy etc.

If you have to borrow to purchase new there's the added costs of interest rates etc. on the other hand if you have €40k in savings and invest it wisely it could earn you an nice nest egg while your current car does the business and owes you nothing by now except fuel & service. Bear in mind that your all new shiny tin box with an electric motor will require service & repairs too.

The moral of the story is that it's the original capital outlay that's expensive in the long run and not just the fuel & service. If you decide to get rid of you current vehicle my advise is to buy a good used model with lowish mileage, let some other fool, who has more money than sense, take the hit on the new one and believe it's a big financial hit.

But at the end of the day and in the final analysis it's your hard eared money and how you spend it is entirely your business.

All new cars are expensive now. EV’s aren’t particularly expensive anymore.

Regarding saving money if you go electric - rest assured that will not happen. The only way you could possibly save money is if someone gifted you an electric car and took away your current ICE car without any money changing hands.

This and similar arguments get trotted out every time somebody posts about changing their car. And although on the face of it, it seems to make sense, in actual fact it doesn't.

Firstly the OP has a big repair bill coming on his existing car. If he keeps it, that has to be paid and there's no guarantee there won't be further big bills down the road. There comes a time when it's not economic to continue and the OP has decided that this is the time.

Secondly, we all know that cars are depreciating assets. It could be argued that they're not assets at all and actually liabilities with constant expenditure and depreciation. At some point a new (either new to the OP or brand new) has to be purchased to replace the existing one. That's just a fact of vehicle ownership and there's no escaping it. How often that happens is down to the individual owner and their particular circumstances.

There are things the owner can do to mitigate some of the costs. Buying second hand is one way; a one year old low mileage or ex-demo is one way of doing this. But once the decision is made to change (for whatever reason), trying to mitigate costs is valid and possible. EVs will reduce running costs (all else being equal), so it's a valid question to ask how much of a saving in those costs can be made.

It's been pointed out on this thread that the OP could make an annual saving of ~€3,000 pa on diesel v electric, there's also road tax savings and likely service and maintenance costs (many EVs come with free servicing for the first 3 years). So at the very least, the OP could see a saving of ~€10k over three years vs his current car.

Do you own the diesel or do you have a loan/PCP finance for the diesel or is it debt free?
Will you be getting a loan/PCP finance for the EV?

Had the OP posed the following question ''I am about to buy an new car and have a budget of €40,000 should I buy ICE or electric?'' - then it could be argued that you have made some valid points. But his/her major concern was the annual fuel cost of current diesel vehicle and pending repair bills. Of course all cars that have clocked up high mileage will incur some high repair costs - the fact that the OP's car will cost a third of it's value to repair is not, on it's own, a reason to bin it. Spending say €2k on a car worth €6k should prolong it's life for an extra 3 to 6 years with just the normal service & minor repair costs in between. Diesel engine cars, provided serviced regularly, can clock up 250,000 to 350,000 miles without major issue - based on the OP's annual mileage, his/her car should be motoring away for 15 to 18 years. In the meantime had the OP purchased a new vehicle be it ice or electric it would have depreciated considerably in that period.

As an aside the average lifespan of the battery in an electric car is from 9 to 12 years and the cost of fitting a new battery would be 4 to 6 times the value of the car depending on model etc. But after the first 3 years the range of the battery decreases incrementally as the range anxiety of the owner increases !

The real-world battery lives of EVs are proving remarkably resilient. I wouldn't worry about that at all (and indeed I don't having now switched to fully EV with 2 cars - and having researched it in detail). As one example, Richard Symons recently plotted UK real-world data to show this on his YouTube channel - nothing under c. 90% including cars with >200k miles

That’s a substantial saving but if you hadn’t traded down and bought the equivalent BMW i5, it would be a different story.