Only as big as needed and NO BIGGER. There is no such thing as “bigger is better” when it comes to pool pumps. With variable speed pumps, owners can maximize efficiency and get the power (for spa jets, water features, cleaning systems etc.) they need for special circumstances. When the pool is filtering, we actually want the lowest horse power possible so that we have the greatest efficiency. We do NOT want the filter pump running at high speeds or high horsepower.