Increasing the Energy Efficiency of your Hot Tub or Spa
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Hot tubs and spas are more energy efficient than ever, and manufacturers have made great gains in efficiency in the last ten years. New insulation materials and better methods of applying it, and energy star certified pumps, blowers and heaters are leading the charge.
How energy efficient is your spa or hot tub? A spa uses electricity to power the pumps, blower, heater and lights. A well insulated spa, with a good spa cover should be able to operate for about $20 per month in electricity. If you spend more than that - read-on for tips on greater hot tub energy efficiency.
The price of a spa, in part, depends on how well it is insulated. Top of the line models have "Full Foam" insulation, injected between the spa shell and cabinet. When the quality and density of the foam is very high, that temperature loss out the sides and bottom is very low. A cheaper method of spa insulation is to simply spray the underside of the spa shell with half an inch spray foam. Lining the cabinet interior walls with foil covered fiberglass insulation or a rigid insulation panel is another way to reduce spa insulation cost, and spa efficiency.
To improve your spa insulation, you can buy DIY spray foam kits, or use rigid insulation panels to line the inside of the cabinet. You can also use fiberglass insulation bats, laid around the spa shell or up against the cabinet.
How's your spa cover doing? What's on top of your spa makes a big difference in the energy consumption of a spa. It's unfortunate that most spa manufacturers include a flimsy spa cover with their new spas. It's common that these last only a few years, and that's good, because the R-value of such spa covers is very low. A waterlogged spa cover is even worse. If you can feel steam or heat coming out of gaps in your spa cover, imagine it as dollar bills with wings.
A new spa cover is a sure way to dramatically effect your energy usage. The thicker the foam, the more heat trapping ability a spa cover has, so get a good one! Another way to reduce heat loss from the top is to use a floating spa blanket. It floats on the water, reducing the workload of your spa cover, while also protecting your spa cover from excess moisture.
Most spa heaters are electrical immersion elements. These heat up, like a coiled electric cooktop burner, and transfer the heat to the water. Most spa heaters are as energy efficient as they can be - it's up to you to use your spa heater wisely. Do you really need to have it cooking at 105° if you only use it on weekends? Or when airing out the spa cover, or after shocking the spa - might you turn down the heater?
Keeping your spa at 95 degrees, and then heating up to 105 just before getting in makes sense, unless you're like me, and use the spa nearly every night. I turn the spa heater way down to 75 during vacations or short trips away from home. This is not only to save electricity, but to discourage anyone from using the spa while I'm away.
Some spas have one two-speed pump, and some spas have two pumps, a low speed pump for circulation, and a high speed pump for jet action. Modern variable speed pumps are popular on pools, but I've not seen them used on spas. When your spa pump eventually fails, look at energy efficient spa pumps as a replacement. These operate with reduced amperage draw and larger capacitors to be up to 50% more efficient than standard pump motors.
Spa pumps may typically run on low speed for 18 hours per day and high speed for 4 hours. You can however, make adjustments to the timer, to operate less on high speed, or have a few hours daily where it doesn't run at all. If you experiment closely with pump run time, you can determine the minimum requirement, just before the water starts looking a little hazy. Increase run time above this threshold, and you optimize the energy usage of your spa pump.
The spa blower injects bubbles into the spa jets, for real hydro-therapy. It makes the water force feel stronger, but at the same time, is gentler than water alone. Using your spa blower tends to cool off the spa water somewhat, requiring your spa heater to work a little bit harder.
When your spa blower eventually fails, you can look to an energy efficient spa blower, or downsize to a smaller blower, or just go without one! To me, a nice hot soak, without all the turbulence, is more relaxing than using the air blower. You can always open up the passive air intakes, to add air without operating a blower motor.
In summary, to increase the energy efficiency of your spa or hot tub:
- Buy energy efficient pump and blower motors; look for the Energy Star logo.
- Use a quality built spa cover, and a floating foam blanket.
- Add extra insulation around the spa shell or cabinet.
- Experiment with your pump run time; and operate it less.
- Turn down the heat! 10 degrees can save 20%!
Happy Hot Tubbin'
Hot Tub Works