The state of Colorado is giving people tax credits that will offset the cost of turning a hybrid car into a full plug-in electric by as much as $6,000. These conversions normally cost in the $12,000 range, so this is a pretty significant discount.The folks at Gas2.0 run the numbers and estimate that, even with this subsidy, it would take 11 to 17 years for the retrofit to pay itself off in gas savings. So from a self-centered economic perspective it might not make a lot of sense. But you know what? Some people will still do it because they're happy to pay a little more for the opportunity to mitigate their impact on the environment we share. And that bodes well for humanity in general.It's also worth pointing out that retrofits like this are great because they allow a hybrid owner to move to a full electric without an entirely new car being built (itself a costly process). I wonder if there's anything Toyota could do to in the engineering of the Prius to make updates like this cheaper and easier. They might even get into providing the service themselves.