The reason why Tesla is able to pay the Dept of Energy loan early is because of a secondary stock and bonds offering worth about >850+ million. In another words, Tesla is raising funds by generating more debt (from bondholders) and diluting share value (from shareholders), roughly about 3.5 mil out of 40 mil float, and using that money to pay the US govt. TSLA rose on the news despite diluting shareholders is because…
Considering the terms of the government loan were very favorable (rates equal to the interest rates on Treasury notes in 2010) it doesn't make sense to me that they would want to pay it off early and get rid of all that liquidity. As a quickly growing company didn't they have something better to spend that $450 million on?
See http://www.businessinsider.com/elon-musk-borrows-150-million...
There is says that the loan requires Musk to have a 65% ownership of the company which of course is expensive to maintain when they are raising money.