When to use this calculator
- When you need a fast estimate before making a bigger decision.
- When you want to compare a few scenarios using the same assumptions.
- When you need a clearer starting point before using a detailed quote or formal document.
- When you want to sanity-check a figure you have seen elsewhere.
A worked example
These are the example figures the calculator opens with.
| Input | Value |
|---|---|
| Battery Capacity (kWh) | 60 |
| Full Charges Per Week | 2 |
| Electricity Price (NZ$/kWh) | NZ$0.24 |
| Range Per Full Charge (miles) | 200 |
For those figures the calculator returns:
- Cost per charge: NZ$14.40
- Monthly: NZ$124.70
- Annual: NZ$1,497.60
- Per mile: 7.20p
Method & assumptions
This calculator estimates the cost of charging an electric vehicle based on your battery capacity (in kWh), the charge level you are starting from and aiming for, and the electricity rate you are paying in pence per kWh. A charging efficiency factor of approximately 10–15% is applied to account for energy lost as heat during the charging process, which means the energy drawn from the grid is slightly higher than the net amount stored in the battery. The calculator covers home and public charging scenarios — simply enter the appropriate rate for each. It does not account for subscription fees charged by some public charging networks, which can affect the effective cost per kWh when calculated across low-frequency sessions.
Common mistakes
- Using an assumption that is not supported by a current local quote, bill, statement or official source.
- Treating a generic estimate as a lender, provider, payroll or tax authority decision.
- Mixing monthly and annual inputs without converting them consistently.
- Testing only one scenario instead of checking how a cautious assumption changes the result.
What to do next
- Run a second scenario with a cautious assumption so you can see the downside clearly.
- Compare the result with the related calculators below before making a decision.
- Check current local rules, eligibility and provider terms before applying or committing money.
- Keep a record of the assumptions so you can update the estimate when a quote, bill or pay figure changes.