Goal

To find how much different fuel efficiencies cost in terms of dollars per year.
I want to estimate this value for the next 10 or so years.

Assumptions

I'm estimating the average price per gallon of gas (over the next 10 years) to be \$4.50. It is around $3.60 now, I adjusted for inflation, and counter-adjusted for the time-value of money.
I'm estimating that we will drive about 14,000 miles per year (based on the last 3 years).

Data



In [1]:

    
price_per_gallon = 4.50 # dollars per gallon
miles_per_year = 14000.0 # miles per year

Calculations



In [2]:

    
def price_per_year(mpg):
    return (miles_per_year / mpg) * price_per_gallon



In [3]:

    
# Compare fuel efficiencies between 15 mpg and 50 mpg
mpg_list = range(15, 51)
price_list = [price_per_year(mpg) for mpg in mpg_list]



In [4]:

    
def setup_graph(title='', x_label='', y_label='', fig_size=None):
    fig = plt.figure()
    if fig_size != None:
        fig.set_size_inches(fig_size[0], fig_size[1])
    ax = fig.add_subplot(111)
    ax.set_title(title)
    ax.set_xlabel(x_label)
    ax.set_ylabel(y_label)

setup_graph(title='Cost per year for each mpg rating', x_label='mpg', y_label='price', fig_size=(14,8))
_ = plot(mpg_list, price_list)

Example mpg differences in price

1 mpg difference (29 mpg to 30 mpg)



In [5]:

    
price_per_year(29) - price_per_year(30)









    Out[5]:





72.41379310344837

5 mpg difference 20 mpg to 25 mpg)



In [6]:

    
price_per_year(20) - price_per_year(25)









    Out[6]:





630.0

5 mpg difference (25 mpg to 30 mpg)



In [7]:

    
price_per_year(25) - price_per_year(30)









    Out[7]:





420.0

5 mpg difference (30 mpg to 35 mpg)

Note the diminishing returns as fuel efficiency increases



In [8]:

    
price_per_year(30) - price_per_year(35)









    Out[8]:





300.0

5 mpg difference (35 mpg to 40 mpg)



In [9]:

    
price_per_year(35) - price_per_year(40)









    Out[9]:





225.0

10 mpg difference (20 mpg to 30 mpg)



In [10]:

    
price_per_year(20) - price_per_year(30)









    Out[10]:





1050.0

10 mpg difference (25 mpg to 35 mpg)



In [11]:

    
price_per_year(25) - price_per_year(35)









    Out[11]:





720.0

10 mpg difference (30 mpg to 40 mpg)



In [12]:

    
price_per_year(30) - price_per_year(40)









    Out[12]:





525.0

10 mpg difference (40 mpg to 50 mpg)



In [13]:

    
price_per_year(40) - price_per_year(50)









    Out[13]:





315.0