What BTU rating should I look for in a heater for an above-ground pool?

Get a heater rated for at least 100,000 BTUs, and you’re safe for 99% of above-ground setups. The sweet spot is 100,000 to 150,000 BTUs — 100k works for most, but bump to 150k if you’re in a colder climate or want faster warm-ups. Oversizing isn’t wasteful; it just heats faster and shuts off sooner.