Energy Audit and 5 Hot Tub Energy Saving Tips For Winter

Hot Tub's Ready to Go, Using Power All Winter

by Don Ames,

Finding a new address can be a little rough out here in the country. It doesn't help when the Google Map misses the important fact that a road is actually a dead end and it doesn't connect with another road like Google thinks. So I find two dead end roads instead of a nice continuous loop. And, as is always the case, I am on the wrong dead end. Oh well, Lewis and Clark probably had to do a little backtracking too.

The home I am auditing today is what I call an "unfortunate neighbor" home. On the way down the gravel road, I have the privilege of passing "through" the neighbors property. There is no doubt that this neighbor operates a recycling business in the front yard. Well, in the front yard, the side yard, the back yard and the hillside across the road.

When I see a budding business like this, two things come to mind. One is the amount of toxic fluids that gets released into the ground like oil, gas, antifreeze, brake fluid, transmission fluid, paint, grease, etc. The other thing I wonder about is who the lucky soul is going to be that gets to clean up this mess. Business enterprises like this tend to just go away someday leaving the business stockpile behind.

Country Recycling

Despite the neighbors, the audit today is taking place at a well kept manufactured home that sits next to a beautiful stream. There are plenty of big rocks, big trees, and open space. The 2001 home is set on a block foundation with a large deck out back that over looks the stream. A very nice jetted hot tub sits off one end of the deck.

Hot Tub Power:

As I stood on the front deck listening to the cascading stream, I decided to take a look at the hot tub.

The homeowner has one of the maintenance doors open and is working on something inside.  It seems a lightening storm has recently knocked out the power board. The Spa Guy, according to the homeowner, has installed a new board that is suppose to be a little smaller and offer some energy savings. The homeowner was just getting the tub up and running again.

Lightening Storms and Electronics:

Lightening storms can be hard on electronic devices. Whether you're in a lightening storm area or not, if you don't have a surge protector on your valuable electronics, I would suggest you get one connected before the day is out.

Mother Board

A hot tub has an electronic dashboard that uses power continuously, a water pump that circulates the water through the filter and a stronger, larger pump that powers the water jets. And, of course, a hot tub has a water heater. Between the pumps, heaters and electronics, a hot tub can contribute significantly to a  power bill.

I ask the homeowner if they use the hot tube often and I learn that they often use it several times a week, even through the winter. I visit many homes where the hot tub is kept warm and circulating all the time, yet never used. Many homeowners  feel that keeping the ol' tub going keeps it from freezing and helps keep the water fresh by circulating the water cleaning chemicals.

I remind people that timers can be added to a hot tub so the tube is active only a couple times a day for an hour or two. The timer allows the hot tub to run often enough to keep the tub and water in good condition, but keeps the tub from using continuous power.

Here's how one happy tub owner has calculated the power usage.

"Your 310 kWh in 29 days represents slightly less than half a kilowatt per hour over that period, which is the energy necessary to compensate for a temperature drop of a bit under 1/2 degree per hour in a 400-gallon spa. Seems like a reasonable ballpark figure to me. (Back-of-the-envelope math: 400 gallons of water is about 3,300 pounds. It takes one BTU to heat a pound of water one degree F, and a kilowatt-hour is roughly equivalent to 3,400 BTU. Therefore it takes a tad under one kilowatt-hour of energy to raise the temperature one degree in a 400-gallon tub. 29 days = 696 hours. 310 divided by 696 = 0.45 kilowatts every hour, 24 hours per day, for 29 days, on average.)"

With the cost of electricity at 15 cents a kilowatt/hour, the hot tub is costing $46.50 a month or $558 per year.


Factors That Contribute to an Energy Efficient Hot Tub.

1.  R-Value:

A hot tub has an R-value that represents the insulation in the shell and floor. The higher the R-Value, the slower heat passes through the shell to the outside.

2.  Foam Insulation:

Look for a lot of foam insulation that retains heat and does not react to moisture. Icynene foam is a good product to insulate a hot tub.

3. The Hot Tub Cover:

Upgrading the cover can increase the insulation value and contribute to lower heating costs.

4.  Circulating Pump:

A circulating pump should draw about 0.4 amps. Since this pump runs continuously, look for some efficiency here. The lower the amps, the less it costs to operate.

Hot tub Sections

5.  Standby Wattage:

Or, how much juice does the hot tub use when it is in standby mode? It's best not to make your final decision based on standby efficiency. A tub scores high with low usage here, may not score to well when you need some real hydrotherapy.

Other Energy Efficient Considerations:

A hot tub should not be purchased simply on the strength of it's energy efficiency. If you want a hot tub to soak in, look for low wattage, small pumps, and fewer gallons of water.

If you looking for hydrotherapy because the old body just doesn't want to get out of bed, Up the wattage a little and get some pumps that will make a dent in the skin.

How to Keep the Water Hot:

The actual energy usage to keep your spa hot depends on these three things.

1. Insulation

The amount and kind of insulation in the tub surround.

2.  Cover

To keep the water hot, up-grade to a well insulated and sealed cover.

3.  The outside temperature.

Hot Tub as a Unit

The greater the difference in the temperature of the water and the outside air, the greater effort and energy the tub will need to go through to keep hot.

Well, so far, all this home energy audit has accomplished is to take a closer look at the hot tub. The reason it is important is because the hot tub can be a forgotten energy user, particularly through the winter months. You see it everyday, it has a cover over it, and it kind of gets forgotten.

If your not using it, wouldn't it be fun to unplug the power and drain the water. If you do that, don't forget to check your power bill and see if a little of the expense has drained from it also.

And, if you would like to pick up a hot tub on the second hand market, I know where there is a least a dozen of them at this great recycle place out in the county.

Next Up, a Hole in the wall:

When I walked through the living room I noticed a nice wood stove, I also noticed a heating register mounted about 4 feet up on the interior wall opposite the stove. Can't wait to take a closer look at that!

Thanks for stopping by Detect Energy, hope to see you again real soon, but I won't leave the light on for you...

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Tags: conservation, efficiency, energy savings, hot tub, hot water


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Comment by Greg Fossen on March 19, 2012 at 10:32am

Hi Greg here, from Colorado Home Efficiency Consultants. When I see Hot tubs, I always suggest that they are a good reason to get a solar thermal system. Providing water that is preheated by the sun cuts the hot tub heater power waaay down...

Comment by Tom DelConte on February 29, 2012 at 4:43pm

Agree with Bruce. For what it's worth, I'm operating a 400 gal. hot tub for $9.00 per month electricity at $0.14 per kwh, and $3.00 per month in chemicals. Ours is designed similarly to your illustrations. It's usually in sleep mode at 66F, with occasional use at 98F.

Comment by Bob Blanchette on February 24, 2012 at 10:04am

Agreed, the winter is when hot tubs are used most around here also. In summer, the sun is typically enough to keep the water warm.

Comment by Bruce Navin on February 21, 2012 at 8:32am

Nice article. Although I am not sure why the tub would be forgotten during the winter months. In my experience, that is when it is used the most. During summer time, many prefer the cool water of a pool. 

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