Q. How would I site this source in APA http://www.afdc.energy.gov/fuels/natural_gas_basics.html

Yes, I would treat it as a website with a corporate (in this case, government) author.

The form is straightforward. You can see an example on this Library page - http://libguides.css.edu/c.php?g=41681&p=265017

a). You have an author, in this case the United States Department of Energy.

b).  Often dates for websites appear at the fine print at the bottom of the page. And on this page we see a note that it was updated on November 4th, 2013.

c). Titles can be sometimes tricky based on the way webpages are designed. Since the information on the page is about natural gas, it seems to make sense that the title would be "Natural Gas Fuel Basics."

d).  Last, you need a URL that matches the title.

Once you identify what type of information you are citing, and locate the form in a style guide, then it is just a matter of stringing it together while keeping in mind rules for capitalization, italicizing, punctuation, and indenting.

Ergo:

United States Department of Energy. (2013, November 4). Natural gas fuel basics. Retrieved

     from http://www.afdc.energy.gov/fuels/natural_gas_basics.html

Good luck with finals.