If you're going to have to lay new lines, then cheapest approach is surely to just put cable in the gutter, and then protect it with something similar to those rubber speed-bumps you can bolt into the ground. Downside is the low profile prevents great big connectors/supply units - but would be fine for the equivalent of the domestic-plug....
...I'm meandering now, but wonder if you could retro-fit drain covers to contain chargers...