This very interesting, but how many charging bays are being applied to each store? As on average most people spend around 45 minutes shopping. So my point is you would need at least 20 bays.
And lets not forget that electricity comes from power stations, unless this is all wind powered electricity?.
I see Tesco jumping on this so as they can get in first to market and win over customers. It works with the supermarket petrol stations with lower fuel prices and discount vouchers.
Just a last thought what would stop a non shopper just using to top up?
Rant over lol