How long does it take to heat up a 250 gallon hot tub? I just bought an inflatable hot tub from Meijers.?

Question

I just bought a portable hot tub from Meijers and was wondering how long it takes to heat it up to 104 degrees. I have the filter and heat on to 104.The size of the heater is 1000 watts. The tub only cost $500 and holds 250 gallons. I have had the pump and heater running for at least 10 hrs. and the temperature is only 65 degrees. One person told me it could take about an hour a degree. Is that true? HELP!!

Answer 1

1000 watts equals 3400 BTU per hour.
1 BTU will heat a pound of water 1 degree F in 1 hour.
A gallon of water is 8.33 pounds.
You have 2082.5 pounds of water in the tub.
It will take 2082.5 BTU/hour to raise all the water 1 degree F per hour.
It should take about 40 minutes to raise your tub 1 degree.
This does not take into account heat loss through open top, heat loss around sides, heat transfer losses, etc, so it may take longer.

Answer 2

That's what they don't tell you when you buy one of those tubs. They take forever to heat up and use a tremendous amount of energy to maintain temperature. A friend of mine had one thinking he could take it to parties and provide a tub experience for everyone. He soon found out it took literally days for the tub to heat up to a usable temp. Ambient temp, amount of insulation, original water temp and other factors determine how long it will take to heat but you can expect a couple of days at least. 1kw of heat is also not enough to maintain your temp for more than a few minutes once you start using the tub. It will lose heat quickly. These tubs are good for summertime use only and then only if you don't expect 104 deg. Be happy if you get it to 98.

If you want to use it anytime soon you might consider hooking a hose to your water heater after lowering your water level and filling it from there about 30 gal at a time so the water heater can recover. You will raise the temp faster and probably save energy in the process.

Good Luck!