Saturday, August 9, 2014

Fuel consumption of the Prius and the Corolla.

Prius versus Corolla fuel savings

Questions:

Gas mileage estimates for the Toyota Prius and the Toyota Corolla are presented below.

Fuel Efficiency In Miles Per Gallon
Toyota Prius
Toyota Corolla
City
51
30
Highway
48
42


Driving patterns defined by total miles driven in a year and percent of miles driven in city and in highway for six drivers are presented below.


Six Driving Scenarios
Driver #
Miles Driven Per Year
% City
% Highway
1
10,000
25
75
2
10,000
75
25
3
12,500
25
75
4
12,500
75
25
5
15,000
25
75
6
15,000
75
25


How much gas would the six drivers use in a Prius and in Corolla over the course of a year?

How much would the six drivers spend on gas in the two cars at a price of $3.50 per gallon?

How much would the six drivers spend in gas in the two cars if the price of gas was $4.00 per gallon?


Analysis:  

Discussion of Calculation:

Step One:  Obtain city and highway miles driven.  For driver one city miles = 0.25*10,000 and highway miles = 0.75*10,000.

Step Two:  Obtain gallons of gas consumed in city and highway.   (Note that gallons=mile/(miles/gallon).  So for the first Prius driver Prius City gallons = 2500/51  and highway gallon = 7500/48.

Step Three:  Add city gallons to highway gallons.  For the first Prius driver get 205.

Step Four:  Dollars spent on gas is $/gallon x gallons.  Get $718 at $3.50 per gallon and $821 at $4.00 per gallon.

Results:  


Prius Calculations
Ann Miles
% City
% Hway
City Miles
Hway Miles
city mpg
Hway mpg
City Gals
Hwy Gals
Total Gals
Gas @ $3.5
Gas @ 4.0
1
10000
0.25
0.75
2500
7500
51
48
49
156
205
$718
$821
2
10000
0.75
0.25
7500
2500
51
48
147
52
199
$697
$797
3
12500
0.25
0.75
3125
9375
51
48
61
195
257
$898
$1,026
4
12500
0.75
0.25
9375
3125
51
48
184
65
249
$871
$996
5
15000
0.25
0.75
3750
11250
51
48
74
234
308
$1,078
$1,232
6
15000
0.75
0.25
11250
3750
51
48
221
78
299
$1,045
$1,195






Corolla Calculations
Ann Miles
% City
% Hway
City Miles
Hway Miles
city mpg
Hway mpg
City Gals
Hwy Gals
Total Gals
Gas @ $3.5
Gas @ 4.0
1
10000
0.25
0.75
2500
7500
30
42
83
179
262
$917
$1,048
2
10000
0.75
0.25
7500
2500
30
42
250
60
310
$1,083
$1,238
3
12500
0.25
0.75
3125
9375
30
42
104
223
327
$1,146
$1,310
4
12500
0.75
0.25
9375
3125
30
42
313
74
387
$1,354
$1,548
5
15000
0.25
0.75
3750
11250
30
42
125
268
393
$1,375
$1,571
6
15000
0.75
0.25
11250
3750
30
42
375
89
464
$1,625
$1,857




Potential Fuel Savings Prius over Corolla
Gas @ $3.5
Gas @ $4.0
Corrolla
Prius
Diff.
Corolla
Prius
Diff.
$917
$718
$198
$1,048
$821
$227
$1,083
$697
$386
$1,238
$797
$442
$1,146
$898
$248
$1,310
$1,026
$283
$1,354
$871
$483
$1,548
$996
$552
$1,375
$1,078
$297
$1,571
$1,232
$340
$1,625
$1,045
$580
$1,857
$1,195
$662


Summary   Based on the assumptions used here the savings on fuel consumption from the use of a Prius instead of a Corolla range from $198 to $580 at $3.50 gas to $227 to $662 at $4.0 gas.

Concluding Remarks:

The analysis presented here relied on EPA estimates of fuel efficiency, which differ from on-read fuel efficiency.  On-road fuel efficiency rates are generally a lot lower than EPA estimates and on-road gas consumed varies across drivers.  I expect that differences between EPA estimate and real world driving performance is higher for the more fuel-efficient car.

The Prius costs more than Corolla.  The potential economic gain from purchasing one car over the other would look at additional purchase costs and the difference in the lifetime fuel costs.  

The next post looks at the net present value of purchase costs and fuel costs.


 #Prius
#Corolla
#fuel efficiency





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