> I estimated that 1 minute of artificial tanning is comparable to the 10-15 minutes of sun a day that is recommended.

That doesn't seem right. If you only tan in a strong tanning bed for 10 min (or 15 min in a weaker one), it's equivalent to only about an hour in the real sun around noon. I.e. if you've only been going to a tanning bed, you'll start to burn outdoors shortly after that. (And I'm talking about high-UVB bulbs that develop the long-lasting tan that protects against sunburn, just like the sun itself generates.)

So the difference factor is more like 4-6x, not 10-15x. Honestly, 15x would be insane. Tanning beds aren't as strong as some fearmongerers suggest. And that's assuming full-body exposure.

When you say you artificially tan at home for 1 minute, how? Did you buy your own entire tanning bed? Because if you use the small portable devices (like a Sperti), they're providing only a tiny fraction of what a tanning bed provides, since they're so small.