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<b>Old Guys Rule</b><br>Surfing great Rory Russell at last summer's Legends Surf Classic competition, part of the annual Duke's Oceanfest taking place in August<br>Photo by Dana Edmunds
Vol. 14, no. 4
August/September 2011


Sustainable Soak 

Story by Alan D. McNarie

Photo by Olivier Koning   


All the relaxation without the guilt: Lars Carlson, engineer, tinker and owner of Big Island Spa Source, has invented solar kits to heat hot tubs. Even in cloudy Hilo Carlson's solar spas stay hot year round.

Let’s face
it: The hot tub is a guilty pleasure, or it at least it ought to be when you consider how much energy it takes to heat one. But who wants to think about that while you’re melting into ooze at the end of a long day? Lars Carlson does.


“There are people who would like to own a hot tub, but they’re environmentally conscious so they decide not to,” says Carlson in the crowded showroom of his business, Big Island Spa Source in Hilo. If you’re among those eco-conscious but übertense, Carlson just might be your savior.


When fuel prices spiked three years ago, Carlson saw an opportunity. He designed a solar heating system to operate along with the existing plumbing (so the mod doesn’t void the warranty) in new Baja and Maax spas. He scoured the country for parts, mostly from the swimming pool industry, which had already developed hardware that was resistant to pool chemicals — solar heating panels with pipes made from polyolefin instead of copper, for example.


His invention was a resounding success. A conventional spa like the Baja typically takes ten hours to heat initially and uses about fifteen thousand watts in the process, Carlson says. By contrast, one of his units draws as little as three hundred watts to heat the same tub—in less than four hours. Carlson sells his spas “solar ready”; all a plumber has to do is install the roof panels and connect them to the spas. Conversions cost in the neighborhood of $1,500, but pay for themselves because the only electricity required is for the pump. Baja has been so enthusiastic about Carlson’s kits that it’s begun installing them at its factory. In general, he says, the solar units can do the job even in gloomy Hilo, the rainiest city in the country, where his tub sometimes gets so hot that he doesn’t even put the cover on.