What size heater do I need for an above-ground pool?

100,000 BTUs is the sweet spot for most standard above-ground pools up to 24 feet round (10,000-15,000 gallons). It heats the pool in 12-24 hours without being overkill or short-cycling. Bump to 150,000 BTUs only if you live in a cold, windy climate or want to swim in early spring or late fall. A 100,000 BTU heater with a solar cover feels like cheating.