EV Charging Cost Calculator

The cost to charge your EV is calculated by determining the energy required to move from your current State of Charge (SOC) to your desired SOC. This is done by calculating the charge window (difference between desired SOC and current SOC) as a percentage of your battery's total capacity in kWh. That energy requirement is then multiplied by your local electricity rate (cost per kWh) to provide the total charging cost.

Cost per mile is influenced by the vehicle's efficiency, which is measured in miles per kWh. EVs with higher efficiency (more miles per kWh) require less energy to travel the same distance, resulting in a lower cost per mile. Factors such as vehicle weight, aerodynamics, tyre type, and driving conditions can also impact efficiency, causing variations between models.

Electricity rates vary significantly by region, depending on factors such as local energy sources, infrastructure costs, and time-of-use pricing. For example, charging in areas with high electricity rates or during peak hours can be considerably more expensive. Conversely, regions with low-cost renewable energy or off-peak discounts offer more affordable charging options. This calculator allows you to input your specific rate to reflect regional variations accurately.

One common misconception is that charging an EV is always cheaper than fueling a petrol car. While this is often true, it depends on electricity rates and the efficiency of the EV. Another misconception is that fast chargers are always the best option. While convenient, they typically have higher per-kWh rates, making them less cost-effective for regular use compared to home charging. This calculator helps clarify these costs by providing precise estimates based on your inputs.

To minimize costs, consider charging during off-peak hours if your utility offers time-of-use rates. Additionally, use a home charger with lower electricity rates rather than relying on public fast chargers. Maintaining your EV for optimal efficiency, such as keeping tyres properly inflated and reducing unnecessary weight, can also lower your cost per mile. Finally, pairing your EV with renewable energy sources like solar panels can further reduce costs and environmental impact.

Battery degradation reduces the total capacity of your EV's battery over time, meaning it can store less energy. This affects long-term charging costs because you may need to charge more frequently to compensate for the reduced range. However, the calculator assumes the full original capacity of your battery for its estimates. If your battery has degraded significantly, you may need to adjust the battery capacity input to reflect its current usable capacity for more accurate results.

The miles per kWh input directly determines how efficiently your EV converts energy into distance travelled. A higher miles per kWh value means your EV requires less energy to cover the same distance, resulting in a lower cost per mile. Conversely, a lower efficiency increases the cost per mile. This metric is important for comparing EVs and understanding how driving habits and conditions, such as highway speeds or cold weather, impact your overall efficiency.

Industry benchmarks for EV efficiency typically range from 3 to 5 miles per kWh, depending on the vehicle type. Electricity rates in New Zealand, for example, average around $0.14 per kWh, but can vary widely. Use these benchmarks to compare your EV's performance and costs against averages. If your calculated cost per mile is significantly higher, it may indicate inefficiencies in your vehicle or driving habits that you can address to optimize costs.