TP done properly can be very energy efficient. Clearwater does it properly. The outside is sealed. There is no insulation on the shell and the outer insulation has a reflective layer. From what I understand, no insulation on the shell is an integral part of this working. By putting it on the shell (in a tp design) you are preventing the heat from the equipment compartment from also warming the shell which contacts the water. Clearwater also uses an insulated, floating floor. Again, from what I understand, this is another important factor in this working well. Isolating the spa from the cold ground or cold air under your deck. They also don't use low density expanding spray foam, but a rigid, dense board insulation with the reflective layer.
It's been stated ad naseum, but all TP are not created equal. TP spas can be efficient, and Clearwater Spas are one of them. I'm not educated in thermodynamics or anything, but my anecdotal evidence shows CW to be a very efficient TP spa with a concept that makes sense. They should be $10 - $25 per month here in Colorado. This is what we tell our customers and have never had anyone come back saying that it was inaccurate.
