A few years ago I searched for a website that would allow me to compare total cost of ownership of any two vehicles given my estimated costs. Not finding anything, I put together a spreadsheet and shared it on Google Drive.
I've now updated it to allow plug-in hybrids, and fixed other minor issues. It's now capable of comparing any two vehicles that use petrol, electricity, or a combination of both. It also provides lots of other data such as fuel or electricity cost per mile.
Make sure you enter values in each cell even if the number is 0, or you don't know what to put. You can skip some of the fields by entering 0 and still get a relative cost difference between vehicles. You can enter info for just 1 vehicle if you only want to know the total cost of ownership, but aren't interested in a comparison with another vehicle.
Since this is a public sheet, some fields are locked to prevent the formula or description getting messed up. I recommend downloading it so you have full control to modify, and won't accidentally fight someone else who is using it at the same time.
Let me know if there are errors, I need to clarify something, or add features.
Note that the "Estimated % of miles driven on battery alone" field must be answered. If the vehicle is petrol only, enter 0. If it's EV only, enter 100. If it's a plug-in hybrid, estimate what percentage of miles will be run on battery alone.
Here it is:
https://drive.google.com/open?id=1rb...2dCJSLxp5ne6Q4
The link is in my signature too.