What is the lowest temperature I should maintain during the week when I'm not using hot tub?

[newtubuser413]

I just got a hot tub a month ago and things are going well.  It heats up 1.5 degrees an hour and I usually only use it on friday to sunday nights so I would keep it at 90 degrees during the week and Friday morning I turn it up to 104 in the morning and by night time it's all set.  My question is, can I set it to 80 degrees?  75 degrees even to save more energy during the week since I'm not using it?  I tried searching but haven't found a definitive answer.  Some people say it takes more energy to heat up, which really doesn't make a lot of sense to me...but I may be wrong.  My hot tub is LifeSmart LS200.  Thank you!

[RDspaguy]

2 hours ago, newtubuser413 said:

Some people say it takes more energy to heat up, which really doesn't make a lot of sense to me...but I may be wrong.

It takes alot more energy to heat up at fill-up than to maintain it, so when talking cost on your bill, you will definitely see it when you drain and refill.

If used in economy mode, so that the heater can only run when the pump is already running for a filter cycle, it can save you a few $.

Obviously, more heat will be lost the greater the difference between water temp and ambient air temp, but with a well insulated spa and a good cover this should still be minimal.

Letting it get cool, then heating all a once will cause longer run time on the heater, like at fill, and will make any relay or heater issues more likely to show themselves. But the less often the relays switch the longer they are likely to last.

You can set it as low as it will go if you like. You already know how long it will take to heat up.

[newtubuser413]

Thank you!  So much to consider!  I'm less concerned with heatup time...its more around the total electricity/energy spent between:

1: maintaining the temperature at 100 + heat up to 104

2: maintaining the temperature at 90 + heat up to 104

3: maintaining the temperature at 80 + heat up to 104

Sounds like #3 will spend the least amount of energy, however as you mentioned relay issues likely to show, but then again it it may last longer...sounds like I got my answer.

Thanks again!

[waterbear]

On 1/20/2021 at 11:37 PM, newtubuser413 said:

Sounds like #3 will spend the least amount of energy

It also depends on how quickly the spa loses heat when it's not in use but kept covered and there are several factors that can affect that such as how well the tub and cover are insulted, how efficient your heater is,  and the ambient temperature, as @RDspaguysaid. You might find that it takes less electricity to maintain the heat in the covered spa between use than to heat it up from 80 or 90  degrees when you want to use it. The heater will only come on when the temperature drops and it takes a lot less energy to heat the water a couple of degrees to maintain the temperature than to heat it 10 or 20 degrees. My suggestion, if you have some way to track the electricity used by the spa try it both ways, letting it cool and reheating and maintaining the heat at the desired level and see which is more cost effective.

The ONLY caveat is if you are using a Nature2 with MPS as your sanitizer. SIlver/MPS is a sanitizer at elevated water temperature so I would keep your temperature no lower than 100 if this is your sanitizer system to make sure your water stays sanitized.

[Cusser]

As a scientist, I will say that the heat loss is greater per unit of time when the heat source (the spa) is more different from the environment.  So - unless you're on a "demand" type of electric rate, the least overall amount of electricity would be used when the spa temperature is lower.  For example, 6 months of the year - Arizona summer - I don't add ANY heat to the spa, we used to use this as our "swimming pool" when the kids were little.

Compare your question to how many minutes per hour a home air conditioner must run when it's 115F Arizona-hot outside as compared to when it's 80F outside.

 

[waterbear]

On 3/20/2021 at 10:43 AM, Cusser said:

Compare your question to how many minutes per hour a home air conditioner must run when it's 115F Arizona-hot outside as compared to when it's 80F outside.

Apples and oranges. You are comparing a refrigeration unit (the AC) or or a heat pump (reverse cycle unit) to electric heat (a water heater is a better analogy since it uses electric heating elements to maintain hot water in a tank, only in this case the tank is the tub.