Get a 1.5 HP variable speed pump for a 20,000-gallon pool.

That’s the sweet spot. Most pools in this range do best with a 1.5 HP variable speed. It gives you enough flow to run a cleaner or a solar heater, but you can dial it down for daily filtering and save a ton on electricity.

If you go too small (1 HP), you might struggle to push water through long pipe runs or a high-head setup like a heater or spa jets. Too big (2 HP+), and you’re overspending on the pump, plus you might need to upsize your pipes to avoid cavitation. Oversized pumps also waste energy unless you keep them on low—at which point why pay for the extra horsepower?

Check your plumbing diameter too. If you have 1.5” pipes, a 1.5 HP pump is fine. If you have 2” pipes, you can even handle a 2 HP if you really want, but 1.5 is still plenty. And always, always get a variable speed—single-speed pumps are energy hogs and many states are phasing them out anyway.

Future you will thank present you for the lower electric bill.