EV Charging Cost

Calculating Your EV Charging Cost

Charging cost equals the energy drawn from the wall, multiplied by your electricity rate — and the energy drawn is always a bit more than what actually reaches your battery, since some is lost as heat during charging. Enter your EV’s battery capacity, how much charge you’re adding, your home electricity rate, and (optionally) your charger’s efficiency, your EV’s own efficiency, and a comparable gas vehicle’s MPG and fuel price, and this calculator returns your estimated charging cost, your cost per mile, and how that compares to filling up with gas.

This is distinct from the Electricity Cost Calculator calculator, which estimates your whole household electric bill from usage and rate rather than one vehicle’s charging session.

The Formula

$$\vB{\text{kWh to Battery}} = \vA{\text{Battery Capacity}} \times (\vC{\text{Charge Added \%}} \div 100)$$ $$\vD{\text{kWh from Grid}} = \vB{\text{kWh to Battery}} \div (\vE{\text{Charging Efficiency \%}} \div 100)$$ $$\vF{\text{Charging Cost}} = \vD{\text{kWh from Grid}} \times \vG{\text{Electricity Rate}}$$ $$\text{Cost per Mile} = \frac{\vF{\text{Charging Cost}}}{\vB{\text{kWh to Battery}} \times \text{Vehicle Efficiency (mi/kWh)}}$$

Worked Example

A 60 kWh battery charged from 20% to 80% (60% added), at 90% charging efficiency, with electricity at $0.18/kWh, on a vehicle that travels 3.5 miles per kWh, compared against a 30 MPG gas vehicle at $4.28/gallon:

1. kWh to Battery: $\vA{60} \times (\vC{60} \div 100) = \vB{36} \text{ kWh}$.
2. kWh from Grid: $\vB{36} \div (\vE{90} \div 100) = \vD{40} \text{ kWh}$.
3. Charging Cost: $\vD{40} \times \vG{0.18} = \vF{7.20}$.
4. Miles Added: $\vB{36} \times 3.5 = 126 \text{ miles}$, so cost per mile is $7.20 \div 126 \approx 0.057$.
5. A comparable gas vehicle costs $4.28 \div 30 \approx 0.143$ per mile — charging is roughly 60% cheaper per mile in this example.

Key Factors to Consider

• DC fast charging typically costs more per kWh than home Level 2 charging. Public fast chargers often carry a premium rate compared to home electricity, and can also have lower charging efficiency at very high charge rates — running this calculator with your public charging network’s actual rate (rather than your home rate) gives a more accurate cost estimate for road-trip charging.
• Time-of-use electricity rates can make charging cost meaningfully different depending on when you charge. Many utilities offer lower overnight rates specifically to encourage EV charging during off-peak hours — scheduling charging sessions for the cheapest rate window can noticeably reduce the effective cost per mile.
• Battery degradation over the vehicle’s life can slightly reduce usable capacity and efficiency. A newer EV typically charges and delivers range more efficiently than the same model after years of use and many charge cycles — this calculator’s inputs reflect the vehicle’s current, real-world efficiency, which may drift somewhat over its lifetime.
• This comparison doesn’t include the total cost of vehicle ownership beyond fuel/energy. Purchase price, insurance, maintenance, and depreciation all differ between EVs and gas vehicles too — this calculator isolates the fuel/energy cost specifically, which is one real piece of a larger ownership-cost comparison, not the whole picture.

Common Mistakes

• Using a flat average electricity rate instead of the rate that actually applies to charging time. As covered above, many utilities charge less overnight specifically to encourage EV charging — using your average bill rate instead of the actual off-peak rate can overstate the real cost by a meaningful margin.
• Assuming 100% charging efficiency. As noted above, some energy is always lost as heat during charging — leaving the efficiency field at an unrealistic 100% understates the true cost pulled from the grid.
• Using a home charging rate to estimate road-trip fast-charging costs. As mentioned above, public DC fast chargers commonly carry a premium rate and can run less efficiently — plug in the charging network’s actual published rate for an accurate road-trip estimate instead.
• Treating vehicle efficiency (miles per kWh) as a fixed number. Highway speeds, cold weather, and aggressive driving all reduce real-world efficiency compared to the manufacturer’s rated figure — a number pulled from a cold-weather commute will understate cost per mile for warmer, gentler driving and vice versa.

Useful to Know

• Public fast-charging networks sometimes bill per minute rather than per kWh, especially at higher power levels — convert a per-minute rate to an equivalent per-kWh rate (using the charger’s actual power delivery) before entering it here for an apples-to-apples comparison.
• The percentage-cheaper-per-mile result is sensitive to both the local electricity rate and the current gas price — it’s worth rerunning this calculator periodically with up-to-date local numbers rather than relying on a comparison done months or years ago.
• This calculator pairs naturally with EV Range Calculator (how far a given charge will take you) and EV Charging Time Calculator (how long that charge will take) for a fuller picture of what a charging session actually costs and delivers.