Martin Eberhard was along for the Tesla Motors ride for quite some time before unceremoniously leaving the company and starting his own blog. As one of the chief architects behind the current Tesla Roadster, he knows more than a thing or two about how it works, but even he is caught off-guard from time to time with how the vehicle works now that there is a shiny Roadster sitting in his garage. The latest interesting bit of information comes by way of Eberhard's blog and involves how much energy the car uses -- get this -- when parked. Astonishingly, the car's battery constantly has coolant run through it, just so long as it's at least half-charged. Because his car is nearly always fully charged, Eberhard's pump is always running. To track its power usage, a meter was installed and Martin was very surprised to find that 22-percent of his car's energy usage was being used while the car sat!
Besides using up precious energy, Eberhard also wonders how long his pump will last, considering that it's running almost constantly. A much bigger issue could be a reduction in the life of the battery, as Eberhard's calculations indicate that his battery's life could be reduced by up to two years or 20,000 miles, and that's a really big deal.
[Source: Tesla Founders]