Electric heat pump for pool/spa in South Florida. What to expect?

[ChadJ]

I am adding an electric heat pump (115-130k BTU) to my 15k gallon gunnite pool spa combo in south Florida. The 500 gallon spa has an overflow into the pool but can be isolated. I do not have access to gas and do not want to bury a tank. My current plan is to heat the pool on weekends during winter months but am HOPING to use the spa many nights of the week year round. Specifically, I'd like to know what I can expect for spa performance on around, let's say 70-75 degree days. For those in south Florida or similar climates that are using an electric heat pump, how long does it take to heat your spa and how hot will it get? I know electric is not ideal for a spa but I don't have much of a choice so I would like to know if I'm setting myself up for disappointment in using the spa at around 102-104 degrees. I understand this will be less realistic on days under 65 degrees or so, but those are rare down here.

Thanks for your help!

-Chad

 

[pooldv]

Your best bet would be to have an insulated spa cover made for it and leave it heated all the time.

 

[ChadJ]

I may have overstated what I meant by the spa being able to be isolated. I can isolate the drain and return to only circulate in the spa when in Spa mode, but that means the pool is not circulating, so I don't think that's an option for me to leave it heated all the time. (Not sure I'd be willing to deal with the cover either.) I know an electric heat pump isn't ideal for a spa, generally speaking, but in South Florida with generally warm temperatures I believe it is feasible. Again, just hoping to get confirmation and/or first hand experience from someone in my climate that uses an electric heat pump to heat their spa and how they feel it works. The heater sales reps will probably tell me I could boil pasta in it after 30 minutes, but I want real life experience to set my expectations. Thanks much for any and all input!

 

[pooldv]

Here are some numbers to chew on.
It takes 1 btu to heat 1lb of water 1°f.
500 gal x 8.33 = 4165 lb of water ÷100,000 btu = .042 hours or 2.5 minutes.
A 100,000 btu heater can raise 500 gallons of water 1 degree in 2.5 minutes.

 

[ChadJ]

Vey interesting. So by that math, it would take about an hour and half to heat up the spa if it started at around 70 degrees. I can live with that. Have automation and wireless connectivity. Thanks for the breakdown! Still hoping someone will chime in who has al electric heater on their pool spa combo in my area. If not (either way really) I will be sure to post my result once I install in a couple weeks.

 

[Fins]

I have a 120 MBH heat pump on my 4'x8' spa. Water temperature is running around 78 degrees F. these days. To heat the spa to 95 degrees is taking around 35 minutes. It will definitely heat it but just be prepared for a slower process than with a gas heater. Happy with the performance of the heat pump and it's pretty economical to run. I did not opt for the heat pump that can also cool the water and in hindsight, I should have sprung for it. Water was 92 degrees for most of August and September.

I'm in Boca Grande in SW FL.