I've been trying to work out the answer to this myself - the maths has changed as electricity prices have gone up. I'm tempted by one of these https://shop.openenergymonitor.com/emonevse-wifi-connected-ev-charging-station-type-2/? As I understand it EV charging works by a fairly simple communication between car and charger so the right amount of power is delivered no matter what car you have, where it is in the charge cycle, and how much power the station can supply. So it isn't hard to make a charger that varies how much power it can supply - according to what Solar is available. But - solar is only available in the day - most people park their cars at home overnight and there is still cheap off peak electricity available overnight. We don't do a lot of miles say 2000 per year at about 3 miles per kwh so about 700kwh at 10p per unit (off peak) that's £70 per year - quite a long payback time At 30p per unit it could save £200 per year which makes more sense - but then in summer I usually try to charge in the - my car draws about 3.5 Kw - the panels provide up to 3Kw If the price of smart chargers comes down, electricity prices go up - or somehow I end up driving a lot more while leaving the car on the drive ... then a smart charger could make sense.