This has some interesting information that seems relevant. This SAE study indicates that 7k BTU should be plenty for 100°F+ weather. All of the tested vehicles (Impala, Camry, Prius, Altima) have more internal volume than one of our trucks.
That number is less than I expected. I would be interested to know more details about the test methodology, but what you see is what I got.
SAE Study of AC Requirements7000 BTU is approximately equal to 2000W of cooling (there are some assumptions in that math, but I don't have a better way to try and compare them).
With the COP of 3 from Kevin above, that works out to about 667W.
Divide that by 13VDC (nominally 12, a lot of alternators put out 14, call it 13 for convenience) and you get 51A needed. With the nominal 60A that this is rated, that is 15% overage for efficiency losses and/or rating estimates.
All things considered, that seems pretty plausible to me and correlates to the SAE rated needs.
@Bartamos: Agreed. But as far I know, there is not an equivalent to amps for measuring effective capacity on these systems. BTU *should* be that number, but it is consistently fudged.
