On a 15' pool? You can get great results with no more than a 1/2 hp, uprated. Not only will you
1)save money on the pump,
2)you'll save money on electricity and
3)it will be quieter.
4)and it will filter BETTER than a 1 hp pump, by far.

15'...Even if you have 4' deep WATER that's barely over 5000 gallons. I have 20,000 gallons and use a 1hp pump (full rated) PLUS solar panels--and I mostly run it on low speed (it's a 2 speed) rather than full speed.

Seriously, I would not even CONSIDER anything bigger than 1/2 horsepower UPRATED for your pool.

Horsepower's good in cars, boats and lawnmowers. But in a pool pump too much is BAD, VERY BAD!