ZapMap have a handy calculator – https://www.zap-map.com/tools/journey-cost-calculator/
I compared the DS3 electric with my current Alhambra over a year & it came to a saving of around £1200 even with my electricity at 14.9 pence per kW.
I did these sort of calculations some time back & have been keeping an eye on electric cars ever since, the simple equation is that it must save enough over a petrol or diesel to fund the extra AP.