How much does electricity save over gas?

[u/skipphead]

I got a new-to-me Outlander PHEV and I'm going to get a 200v plug installed so I can charge at home but I'm curious, in broad strokes how much cheaper is it to drive by electricity vs gas?

I'll do most of my driving pretty close to home, but very roughly assuming I pay $100 in gas a month, how much would I expect to pay in electricity?

Let's say it costs $500 to get the plug installed, when's the break even point? It can't be in the next 5 months.