Comparing electric vehicles to gas and diesel cars requires understanding different energy units and efficiency metrics. Let's break down the numbers to make meaningful comparisons.
Energy Content Comparison
The EPA Equivalency Standard
The EPA established that 33.7 kWh of electricity = 1 gallon of gasoline in terms of energy content. This is used to calculate MPGe (miles per gallon equivalent) for EVs.
Electricity (kWh)
33.7 kWh
= 1 gallon gas equivalent
Used directly by electric motor
Gasoline
1 gallon
= 33.7 kWh of energy
Must be combusted in engine
Diesel
1 gallon
= 37.9 kWh of energy
~12% more energy than gas
The Efficiency Gap
Here's the crucial difference: Having energy is one thing - using it efficiently is another. Electric motors are dramatically more efficient than combustion engines.
Electric Vehicles: 85-90% Efficient
Electric motors convert 85-90% of electrical energy into motion. Very little is wasted as heat.
Energy Flow (100 kWh from battery):
- • 85-90 kWh → Powers the wheels (motion)
- • 10-15 kWh → Lost as heat and other losses
Gasoline Vehicles: 20-30% Efficient
Gasoline engines waste 70-80% of fuel energy as heat. Only 20-30% actually moves the car.
Energy Flow (100 kWh from gas):
- • 20-30 kWh → Powers the wheels (motion)
- • 70-80 kWh → Wasted as heat (exhaust, cooling, friction)
Diesel Vehicles: 30-40% Efficient
Diesel engines are more efficient than gasoline but still waste most energy as heat.
Energy Flow (100 kWh from diesel):
- • 30-40 kWh → Powers the wheels (motion)
- • 60-70 kWh → Wasted as heat
Bottom Line: To move a car the same distance, you need 3-4 times more energy from gasoline or diesel than from electricity. This is why EVs are so much cheaper to "fuel."
Real-World Example: 300 Miles of Driving
Electric Vehicle
Efficiency: 3 mi/kWh
Energy needed: 100 kWh
Cost at $0.13/kWh: $13.00
$13.00
Gasoline Vehicle
Efficiency: 30 MPG
Fuel needed: 10 gallons
Cost at $3.50/gal: $35.00
$35.00
Diesel Vehicle
Efficiency: 40 MPG
Fuel needed: 7.5 gallons
Cost at $4.00/gal: $30.00
$30.00
Savings: The EV costs 63% less than gas and 57% less than diesel for the same distance. Over 15,000 miles per year, that's $1,100-1,650 in annual savings on fuel alone.
Understanding MPGe
What is MPGe?
MPGe (Miles Per Gallon equivalent) allows you to compare EV efficiency to gas cars using a familiar metric. It answers: "If this EV used gasoline, what would its MPG be?"
Formula:
MPGe = (Miles driven ÷ kWh used) × 33.7
Example EV MPGe Ratings
- • Tesla Model 3: 132 MPGe
- • Hyundai Ioniq 6: 140 MPGe
- • Ford Mustang Mach-E: 93 MPGe
- • Rivian R1T: 70 MPGe
Comparable Gas Vehicle MPG
- • Honda Civic: 36 MPG
- • Toyota Camry: 32 MPG
- • Ford Explorer: 24 MPG
- • Ford F-150: 22 MPG
The Takeaway: Even the least efficient EVs have MPGe ratings 2-3 times higher than comparable gas vehicles. Efficient EVs can achieve 4-5 times better efficiency.
Annual Fuel Cost Comparison
Based on 15,000 miles per year
| Vehicle Type | Efficiency | Fuel Price | Annual Cost |
|---|---|---|---|
| Efficient EV | 4 mi/kWh (135 MPGe) | $0.13/kWh | $488 |
| Average EV | 3 mi/kWh (101 MPGe) | $0.13/kWh | $650 |
| Efficient Gas Car | 40 MPG | $3.50/gal | $1,313 |
| Average Gas Car | 28 MPG | $3.50/gal | $1,875 |
| Diesel Car | 35 MPG | $4.00/gal | $1,714 |
| Gas SUV/Truck | 20 MPG | $3.50/gal | $2,625 |
5-Year Savings: An average EV saves $6,125-10,875 on fuel compared to gas vehicles over 5 years (75,000 miles). That's significant money that offsets any higher purchase price.
Environmental Impact
Beyond cost, the efficiency difference has major environmental implications. Less energy needed means fewer emissions, even when accounting for electricity generation.
Electric (US Average Grid)
~200 g CO₂/mi
Includes electricity generation emissions
Gasoline
~350 g CO₂/mi
Direct tailpipe emissions
Diesel
~320 g CO₂/mi
Direct tailpipe emissions
Note: As the electrical grid gets cleaner with more renewable energy, EVs automatically become even cleaner without any changes to the vehicle. Gas and diesel emissions remain constant.
The Bottom Line
Energy Efficiency: EVs are 3-4x more efficient than gas/diesel vehicles
Fuel Cost: Electricity costs 3-5x less per mile than gasoline or diesel
Annual Savings: $800-1,500+ per year on fuel for average drivers
Environmental Impact: 40-60% lower emissions, improving as grid gets cleaner
MPGe: Most EVs achieve 90-140 MPGe vs 20-40 MPG for gas vehicles
