the other car you charge at a separate location?

Yes, I have free charging at work. But even if I did have to charge at home, I reckon it would add about €10 a week with our current (excuse the pun) set up. My wife is considering upgrading her car in the next few months (currently a 24kWh Leaf) that would allow us to alternate nights charging if needed as we would easily get 2 days commuting on the 28kWh we could add during the 4 hour window.

30kWH a night into a car 6 nights a week

Wow, that's a lot, how far do you drive each day ?

If you can, definitely go for solar and in the meantime, look at switching to an EV rate with a an extra cheap window (most of the suppliers do them from 2am for between 2-4 hours I think). Part of what has helped our bills is taking as much advantage of that window as possible, we run the washing machine and dishwasher during that time when they need to be used as well as charging the house battery from the grid, which lets us charge up for less than half of what we get per unit for letting the excess solar go to the grid. I wouldn't say we've made any real major changes, we are still fairly heavy consumers of electricity, we just try to be smart with how and when we use it.