In Colorado, House Bill 1331, the "Incentives for Efficient Motor Vehicles" act, creates or extends tax credits for natural gas conversions, plug-in hybrid conversions, diesel-electric hybrid conversions (don't see many of those) and also supports anti-idling technologies. The credits are maxed out at $6,000 and you can find full details here. H.B. 1331 recently passed the Colorado State House and Senate and was then signed by the Governor. * Please contact your accountant for advice in your situation. Alternative Fuel Income Tax Credits FY Income 67 Enginer Kits with premium installation pack and extended 5 year warranty pack. Alternative Fuels Rebate -- Dealer Information Form DR 0168 Alternative Fuels Rebate -- Government Charitable Organization Application Form DR 0167