A 1/4 HP pump is usually enough for a flat pool cover.

Yes. For most flat pool covers, a 1/4 horsepower pump is the sweet spot.

Flat covers don’t hold much water on top — they’re not like safety covers that can build up inches of standing water. A 1/4 HP pump will clear a flat cover in a reasonable time without being overkill or leaving you waiting forever. A 1/3 HP works too if you want a little more speed or a longer hose run, but 1/6 HP? That’s too slow for anything but the smallest wading pools.

Match the pump to your hose length and how often you plan to use it. If you’re just using it after heavy rain, 1/4 HP is plenty. If you’re leaving the pump on all season, same thing.

The real mistake people make is buying a pump that’s either tiny and takes all day, or way too big (like 1 HP) for a cover that can barely hold an inch of water. Don’t overthink it.