Interesting idea but only really viable for people who can charge at home during daytime in summer and do low miles? For me I think Octopus Go is probably still better deal.
www.goodenergy.co.uk
Anyone use Good Energy? How is customer service?

Zap Flash Tariff: Register your interest
Zap Flash provides four hours of free electricity a week, timed for when there’s a lot of renewable electricity feeding into the energy grid. Meaning you can charge for less, while knowing you’re making the most of electricity generated from sun, wind and water.