I have enjoyed an outdoor hot tub or spa at our home for going on seven years now. Since we live in New York State we do get 5 to 6 months of cold, snowy weather. It is certainly beautiful to use our hot tub on snowy days during the long stretch of coldness.
Hot tubs are simply large heaters and motors which use a considerable amount of energy in their normal usage. I have done some minor experimenting with increasing the energy efficiency of the hot tub throughout the past several years and found a couple of things to be better at saving money and energy.
Energy Efficiency
The first of my original spa covers became very heavy after 4 years of use and I continued to keep it in service on my spa for another year. The cover was absorbing water and chemicals which saturated the insulation rendering it inefficient. During the 5th year I noticed the water temperature would drop about 5 to 6 degrees between the 10 hour idol times where the heat cycle would not turn on. On the 5th year of ownership I finally decided to order a new cover as I was sick and tired of lifting the heavy, water logged old one. When I installed the new cover it was a huge difference on how light it was. I immediately noticed that the water temperature was not dropping 5 to 6 degrees anymore. It would only drop 2 to 3 degrees in that 10 hour span on wintery days.
Then I thought about the 4 inches of air space between the top of the water and the bottom of the hot tub cover. It occurred to me that the hot water was turning to steam, rising up to the cover and condensing back into cold water. I found that roughly 80% of heat was escaping through and around the lid if the hot tub was insulated properly. I purchased an inexpensive solar blanket and cut it to fit on top of the water. This cut my temperature drop of the water down to 1 degree on cold days and some days none if the outside air temperature was in the 40 to 50 degree range. After studying this further I realized that now my cover should last longer as there is less chemicals attacking it from the bottom.
By replacing an old inefficient spa cover and adding an inexpensive solar blanket you will significantly decrease your energy usage, lose less water due to evaporation, and use less chemicals.
Spa Covers and Solar Blankets For Energy Efficiency