Back in the '70's, we saw that sort of thing here in the US for some time, and not just gas stations.
Same here today -- Not just gas stations but many stores, especially smaller ones, put a minimum spend on a credit card.
What to you guys pay per kwh??
At the current exchange rate of £1 = $1.98 my rates are:
Day usage: First 197 kw/h per 3 months, 38 cents per unit, then 22 cents for the remainder.
Night usage (Midnight - 7 a.m. winter / 1 a.m. - 8 a.m. summer): 4.6 cents per kw/h.
All plus 5% tax, no other service charges.