How Much Can I Really Save? Updated 12/27/13

Periodically I will post numbers on the actual cost of driving with CNG.  Keeping with my pledge to maintain honesty, these first numbers may be a little bit inaccurate due to an issue I had with the truck (which I will detail later) which sometimes left me operating on gasoline instead of CNG.  I have excluded those miles traveled as much as I could at this time and I would safely say that my results will be at least 90% accurate.



GGE Purchased       Cost        Miles         Average cost per gge
126.4                      207.40     2033          1.64

Miles per gallon is an expression we all associate with the economy of gasoline engines.  With CNG things are a little different in that we are talking about a gas with varying volumes and pressures.  The best expression to use for capturing the true value of CNG is dollars per mile.  This is simply calculated by dividing the cost by the total miles traveled.  For this set of data, we end up with right at ten cents per mile that it cost me to drive on CNG.

As a means of comparison, lets look at my vehicle had I used gasoline.  My truck gets around  16 miles to the gallon of gas given my typical speed limit traveling.  If we divide my miles (2033) by 16 we get 127.06 gallons. Multiply that number by an average of $3/gallon (prices have dropped lately, but during this data collection period an average of 3 is accurate) and we get $381.12.  Divide this by miles traveled and we get 19 cents per mile.

My  reasonably accurate savings estimate during this period of data collection (about 30 days) was $173.72.


Updated info  12/27/13....For you nerds who will check my math, I am using 16 mpg in calculating the estimated cost of driving on gasoline and  subsequently dollars saved.  This is based on my observation of operating the vehicle using gasoline in my normal every day driving environment.  Mathematically, the CNG MPG came out to 15.4, which is obviously less.   Gasoline is a little more efficient than CNG in creating power and I wanted to allow for that variable in my attempt to capture the most accurate estimation of savings between CNG and gasoline.  My formula for the cost of operating on gasoline is miles driven/16 mpg x 3 dollars per gallon.

GGE Purchased  Cost        Miles Driven   CNG MPG    Dollars per mile
140.9                  235.05      2171                15.4                0.108      


Cost for gasoline  Dollars per mile
407.06                  0.188      

My average cost per gge was $1.66 and I saved about $172 using CNG in this 30 day period.