I have a spa that's 1,600 gallons. What size of BTU heater should I get. want a electric one 240v. Thanks

For a 1,600-gallon spa, you’ll generally want a heat pump around 6,000 – 10,000 BTU, depending on your climate and how often you use it. You can learn more about how to size a pool or spa heater here: hvacdirect.com/size-pool-heater.