I thought this article was worth reading, especially this part…
The math does not add up for this statement that Romney directed at Obama.
The president’s 2013 budget called for elimination of tax breaks for oil subsidies, which the White House estimated at $4 billion per year. Dividing $90 billion — the federal money that Romney claims went toward clean energy — by $4 billion in breaks for the oil industry amounts to 22.5 years, not 50 years.
It’s also worth noting that the $90 billion was not “breaks,” but a combination of loans, loan guarantees and grants through the stimulus program, and they were spread out over several years rather than one, as Romney claimed.
Furthermore, not all of the money went to the “green energy world.” About $23 billion went toward “clean coal,” energy-efficiency upgrades, updating the electricity grid and environmental clean-up, largely for old nuclear weapons sites.
Factchecking the first presidential debate – The Washington Post