In browsing my credit union's loans, they had a "Green Vehicles" loan rate. It's just a .25% APR drop, but hell, might as well. The link points off to a federal program at SmartWay | US Environmental Protection Agency. Sadly, Tesla isn't on the list of vehicles (Green Vehicle Guide | US EPA). I emailed them via the "contact us" section and asked them why. Might help if others do the same. It certainly seems like the Model S would qualify since equivalent luxury cars (e.g. Lexus hybrids) are on the list, plus the Leaf and even the Coda are on the list.
Last year B of A had a special rate for Tesla and a few other green cars. I'm not sure if it was the SmartWay program or not but the rate was too good to pass up even if you could have paid cash. In the end I financed half my Roadster with it. I will follow up by asking them why Tesla isn't on the list, and also invite my local CU to participate. I'd rather support them than B of A.
I heard back from SmartWay and they said the reason Tesla isn't listed is that Tesla hasn't provided them with the specs on their cars.
This is apparently still true as SmartWay doesn't yet list Tesla. I'll have to bug Tesla on this as it could affect where I choose to get my loan from.