You're correct: the ACS summary files do not have this information, so the PUMS is your best bet. IPUMS-USA has county codes, but if a county you're examining can't be identified in the PUMS data, you can use the CHAS data, a special tabulation of ACS…

Can you use PUMS?

If you can use PUMS data, they have cost of utilities.

PUMS variable SCHL

I haven't used the variance replicate tables but I use replicate weights for PUMS data all the time.  I think that all you do is take the 80 x 2 tables (2 tables for each replicate) take the difference

   difference i = total population table i - in…

I thought this was an interesting question, so I wrote a little R code to pull PUMS via tidycensus and create these estimates. If you are not familiar, this is a good walk-through of how to use tidycensus for PUMS data. If you also want standard errors…

Depending on the size of your county/counties of interest, PUMS would work. Larger counties tend to have clear PUMA-to-County crosswalks. Smaller counties may have PUMAs that overlap with adjacent counties. Geocorr can produce the necessary crosswalk…

Thank you! Beth. I will check PUMS. 

You need to use a PUMS file  The vehicle question (household section of the ACS survey form) is #12 How many automobiles, vans, and trucks of one-ton capacity or less are kept at home for use by members of this household?  Split the PUMS data  by using None…