With the 3.6 & 7.2kW chargers they are “destination” chargers & are fairly cheap & don’t push out vast amounts of electricity. If you are parked for an hour you’ll only put in 3.6kW on your car, so at say 15p/kWh, so 54 pence worth. If you drive a fossil you can get 10p off per litre which adds up to a whole lot more, & that’s why Tesco can do these destination chargers for free.
When you use a 22kW AC, or a 50kW+ DC charger it’s a different scale, my Pug e-2008 will suckle 100kW upto 27% & then 72kW up to 54% and then drop to about 52kW to 72% & then I head for the next stop as it slows right down. I wouldn’t expect a supermarket to subsidise these much larger amounts of power & these types of charger aren’t meant as destination chargers, they’re for topping up as part of a longer journey. Tesco have one of these 50kW chargers at one of their stores in Crawley, just down the road from Gatwick airport of course, which makes good sense as people can pick their car up after a holiday, plug it in & pop in the garage shop to get milk/bread etc., & then have enough charge to get them home 100 miles plus away.
I tried using one of the Tesco PodPoint posts at Guildford but the app was still trying to connect when I came out of the store so had stopped after the 15 minutes. I’ve used the posts at a couple of Asda stores, they do 3.6kW & 7.2kW, so I used the 7.2kW sockets with success, they are on Polar so probably do cost a connection charge unless you use a Polar Plus card, which I have as I use Polar ultra-rapids quite often (150kW chargers). And I’ve used some Waitrose chargers, again they were Polar but all newer 7.2kW all round. If I’m somewhere shopping & there’s free electrons being offered of course I’ll plug in as currently it tells the owners (the supermarkets) how frequently these posts are used & the more they are used the faster they will roll more of them out.