What size pump should I get for a 20,000-gallon pool?

Get a 1.5 HP variable speed pump. It’s the sweet spot—enough flow for a cleaner or solar heater, but you can dial it down for daily filtering to save electricity. A 1 HP may struggle with long pipes or high-head setups, while a 2 HP+ is overkill and wastes energy unless kept on low. Always choose variable speed; single-speed pumps are energy hogs and being phased out.