I feel like I'm getting it for free. When I got the car I made some economies to my home electricity usage, and the upshot was a letter from Scottish Power saying that I had been overpaying, was in credit by over £1,000 and reducing my monthly direct debit by £60.
Yes, I was obviously being too profligate with the electricity before, but I simply swore off using fan heaters (adjusted the central heating to compensate) and the tumble drier - except very occasionally. So that has more than paid for the car's consumption.