Tax credits are usually limited to the first number of units sold. The Prius has sold many more than that limit so few tax credits remain. (Maybe some for the PIP) The Volt does not have the problem of excessive sales. JeffD
That credit is for EVs and plug-in hybrids -- Leaf, Volt, Plug-in-Prius, etc. Tax credits for regular (no plug in) hybrids expired in 2010. The Toyota and Honda hybrids sold well enough that their credits ran out several years early.