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Hot Tub Used Every Other Day -- Ways To Save Energy?

Hot Tub Used Every Other Day -- Ways To Save Energy?

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  #1  
Old 01-10-13, 02:29 PM
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Hot Tub Used Every Other Day -- Ways To Save Energy?

The hot tub at my house is used every other day, sometimes daily.

With electric rates in Hawaii at an astronomical $0.44 per kWH, I'm trying to find ways to reduce my electric bill and prevent it from hitting the stratosphere.

Here's some pertinent info:

* The hot tub is running on 220V service
* The hot tub is usually used at 6:00am and 7:00pm
* Desired temperature setting of the hot tub is 97-103 degrees
* The ambient air temperature is 80 degrees daytime, 70 degrees nighttime
* The lowest temperature setting allowed by the hot tub control panel is 80 degrees
* If I set the hot tub temperature to it's lowest setting 80 degrees, it loses about 4 degrees per day.
* Setting the hot tub into "ECONOMY" mode, allows it to drop 15 degrees from the set temperature, but turns on the heater and tries to raise the temperature to the set temperature during the 2 daily filtration cycles, which occur for 2 hours each, 12 hours apart.

Question:
Does reducing the hot tub temperature to it's lowest setting, 80 degrees, save me any money if the hot tub is used 4-5 days a week for 1-2 hours each day? Or should I just keep it set at 97 degrees and ECONOMY mode?

Question:
If so, when would be the best times (12 hours apart for 2 hours each) to have the filtration cycle turn on, which also turns on the heater when it's in ECONOMY mode?


I'm considering building a couple of solar thermal water heater panels and rely on gravity (mounted lower than the hot tub water level) and rising heated water to circulate the water in and out of the hot tub.

Question:
Rather than building thermal solar water heater panels, would I be better off putting the money towards buying PV which will also be used for my whole house?

Thanks
 
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  #2  
Old 01-10-13, 02:35 PM
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I don't see how you can do anything other than permanently lower the temperature if it only loses 4 per day.
 
  #3  
Old 01-10-13, 03:55 PM
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Location: USA
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First question...NO

Last question...PV would be your best bet (thermal would give very little if any payback)
 
  #4  
Old 01-10-13, 10:48 PM
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Thanks for the replies guys. I'm going to just set the spa to 95 and ECONOMY, and try and time the usage of the spa around the filtration cycles (since the pump and heater runs for 2 hours anyway during filtration).

Appreciate the heads-up on PV vs thermal. I'll put the money towards whole-house PV then.
 
  #5  
Old 01-11-13, 06:18 AM
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Is your spa a built-in or portable/free standing unit? I would first consider an insulated cover to cut down on heat loss.
 
  #6  
Old 01-11-13, 10:38 AM
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It is a free-standing spa. I have an insulated cover on it, I think it's 4" thick. I lose about 4 degrees of water temperature over 24 hours.

Yesterday, I set the temperature to 95-degrees, and the 2-hour filter cycle to run at 6:00pm (and 6:00am). It was 95 degrees last night around 7pm.

This morning at 6:30am it was 95-degrees. It had only run the filter cycle (and heater) for 30-minutes since it automatically starts at 6:00am. So, it must not have lost that much heat overnight.

I should check the water temperature at 5:59 am and pm, to get an accurate measure of how much heat is loss in the 12 hours between filter & heating cycles, before the filter & heating cycle starts at 6:00.
 
  #7  
Old 01-11-13, 04:53 PM
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Join Date: Apr 2002
Location: USA
Posts: 201
Typically a home either has natural gas, OR propane....not both. If you don't have natural gas to the home, you wont get it. Go with what the home has.
 
  #8  
Old 01-11-13, 05:52 PM
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You already know how much heat your spa looses over a given time. If you know how many gallons your spa is you can calculate how many btu's you are loosing each day and see how many kw and the cost to heat the spa. Once you know that you can decide if it's worth going to much effort.

8.34 btu are needed to raise one gallon of water one degree farenheight
1 kw of electricity = 3'412 btu
and you've already told us your electricity is $.44 per kw/hr

---
If a train leaves Boston at 10:00 traveling 20 miles per hour... and a train leaves New York at....
 
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