of course shading a parking lot with solar panels improves the parking lot, but i suspect it won't replace nuclear
(and it's probably more expensive than installing solar on hillsides or in fields, and yields less than installing them in deserts, though those may turn out not to matter)
0.47% of the contiguous usa is covered in solar panels, 13778 square miles, or in modern units, 35680 square km https://time.com/6239651/solar-parking-lots-france-us/ (that's what the article says, anyway; i suspect the number is smaller, because https://www.sciencedirect.com/science/article/abs/pii/S02648... only found 2.2 parking spaces per registered vehicle in a more-urban-than-average county; 5 m times 2.3 m times 2.2 times 278 million gives only 7000 square km of parking spaces, perhaps doubling if the parking lot covers twice as much area as the parking spaces in it)
with 21% efficient panels, the 35680 km² figure would yield 7.5 terawatts peak; at a high 30% capacity factor it would average 2.2 terawatts, though the time article linked above only estimates 0.422 terawatts peak. possibly the discrepancy is due to oblique illumination: you can't get the full 1000 watts per square meter of insolation on a horizontal surface like a parking lot except in the tropics, where the us isn't. i suspect some of the discrepancy is so large due to an allowance for spacing the panels apart so they never shade each other. also the time article has an arithmetic error where it says half of 13778 is 4822
if we use, say, 14000 km² and a more plausible 18% capacity factor, without trying to take into account angling the panels and spacing them out, we get 2.9 terawatts nameplate capacity, 0.53 terawatts average
(and it's probably more expensive than installing solar on hillsides or in fields, and yields less than installing them in deserts, though those may turn out not to matter)
consider the usa, one of the most parking-lot-intensive countries in the world, with 278 million cars, almost one per person https://www.forbes.com/advisor/car-insurance/car-ownership-s...
0.47% of the contiguous usa is covered in solar panels, 13778 square miles, or in modern units, 35680 square km https://time.com/6239651/solar-parking-lots-france-us/ (that's what the article says, anyway; i suspect the number is smaller, because https://www.sciencedirect.com/science/article/abs/pii/S02648... only found 2.2 parking spaces per registered vehicle in a more-urban-than-average county; 5 m times 2.3 m times 2.2 times 278 million gives only 7000 square km of parking spaces, perhaps doubling if the parking lot covers twice as much area as the parking spaces in it)
with 21% efficient panels, the 35680 km² figure would yield 7.5 terawatts peak; at a high 30% capacity factor it would average 2.2 terawatts, though the time article linked above only estimates 0.422 terawatts peak. possibly the discrepancy is due to oblique illumination: you can't get the full 1000 watts per square meter of insolation on a horizontal surface like a parking lot except in the tropics, where the us isn't. i suspect some of the discrepancy is so large due to an allowance for spacing the panels apart so they never shade each other. also the time article has an arithmetic error where it says half of 13778 is 4822
if we use, say, 14000 km² and a more plausible 18% capacity factor, without trying to take into account angling the panels and spacing them out, we get 2.9 terawatts nameplate capacity, 0.53 terawatts average
the us uses 100 quads per year https://www.eia.gov/todayinenergy/detail.php?id=56980 which is 3.3 terawatts. 0.27 terawatts of this is nuclear
so conceivably you could replace nuclear with parking-lot solar, but you'll need a lot more solar than that to power the rest of the economy