The cost to charge an electric car depends mainly on how much electricity it uses, the rate you pay and where you plug in. A car that travels the same distance can cost more to charge if it is less efficient or relies on higher-priced public charging. For a useful estimate, start with your expected kilometres and the vehicle’s energy consumption, then use the rates you are likely to pay at home, work or public chargers. The example figures below are illustrative, not current New Zealand tariffs; check your own bill and charger pricing before setting a budget.
The basic calculation is simple: electricity used in kWh multiplied by the price per kWh. The tricky part is working out how much electricity your car will draw from the supply and which price applies to your charging sessions.
Three factors usually make the biggest difference:
Battery capacity matters when estimating the cost of adding a particular amount of charge. It does not, by itself, tell you what the car will cost to run. For that, consider how far you drive and how much energy the vehicle uses over that distance.
There are two practical ways to estimate the expense: calculate the cost of a specific top-up, or estimate energy use over your regular driving. Use the first when you want to know what a charging session might cost. Use the second to build a monthly or annual budget.
If you know how much energy the battery needs, multiply that amount by the number of kWh drawn from the electricity supply and the applicable rate. The dashboard’s battery percentage alone is not a precise measure of energy, so use the car’s usable battery capacity for a rough calculation.
For illustration, imagine an electric car with 60 kWh of usable capacity being charged from 20% to 80%. That adds about 36 kWh to the battery. If, purely for this example, charging efficiency is assumed to be 90%, the supply would provide about 40 kWh. At an assumed rate of NZ$0.30 per kWh, the energy cost would be NZ$12, before any separate fees. These assumptions are not a market price or a guarantee of how a particular car or charger will perform.
For an ongoing budget, use the car’s energy consumption in kWh per 100 kilometres and your expected distance. If the efficiency figure represents energy used by the car, include a charging-loss allowance when converting it to electricity drawn from the supply. If you have a meter or charging record that already shows supply energy, use that figure instead and do not add losses a second time.
As a hypothetical example, a car using 18 kWh per 100 km at the battery and travelling 12,000 km in a year would use 2,160 kWh in the battery. Assuming 90% charging efficiency for illustration, that would require about 2,400 kWh from the supply. At an assumed NZ$0.30 per kWh, the energy charge would be NZ$720 for the year, or an average of NZ$60 a month. Replace every assumption with your own vehicle, mileage, tariff and charging data.
Real-world energy use can differ from a published or dashboard figure. Speed, hills, temperature, heating or air conditioning, tyres, passenger and cargo load, and driving style can all affect consumption. If you do not yet own the car, use a sensible range of consumption figures rather than treating one estimate as exact.
The cheapest option for one driver may not be practical for another. Home charging can be convenient if you have a suitable parking space and access to a charger, while drivers without off-street parking may depend more on workplace or public charging. Compare the prices you can actually use, not just the lowest advertised rate.
| Charging option | What to include in the estimate | Best suited to | Possible limitation |
|---|---|---|---|
| Home charging | Your plan’s applicable per-kWh rate, time-of-use periods and any relevant fees | Drivers with a suitable place to park and charge | Installation, access or parking arrangements may be a barrier |
| Workplace charging | The employer’s price, access rules and any time limits | Drivers who can charge during work | Availability and terms depend on the workplace |
| Public AC charging | The displayed energy rate and any connection, session or parking charges | Drivers who can leave the car charging for longer | Pricing and access vary between providers and sites |
| Public rapid DC charging | The provider’s tariff, any extra fees and the expected session energy | Drivers needing a faster top-up away from home | Convenience and speed may come with a different price from home charging |
| Home solar charging | Any grid electricity used and the value of solar power that could otherwise be used elsewhere | Households able to charge when solar generation is available | Generation and charging times do not always coincide |
In New Zealand, check your electricity plan rather than relying on a general estimate of household rates. Some plans have time-based prices, and the rate that applies to car charging may depend on when the car is plugged in. Compare the full plan and your likely charging schedule before switching: a low overnight rate may not help if you usually charge at other times, and a plan change can affect more than the car’s energy use.
For public charging, check the price shown for the specific charger before starting a session. Providers may charge by energy, time or another stated method, and fees can apply in addition to the per-kWh rate. If a charging app or payment screen shows a session fee, minimum charge, parking cost or idle fee, include it in your calculation. A rate that looks low per kWh may not be the lowest overall cost for a short top-up with an added fee.
Solar can reduce grid electricity used for charging, but its cost is not necessarily zero. If the household would otherwise export that electricity or use it for another purpose, charging the car has an opportunity cost. For a rough comparison, consider the grid power you still need and the value of the surplus solar power used by the car.
Some energy is lost as electricity moves through the charging equipment and is converted for storage in the battery. The amount varies with the car, charger, charging conditions and other factors. A dashboard consumption figure may describe energy used for driving rather than total electricity drawn from the grid, so check what the figure measures before using it in a bill estimate.
Two drivers of the same model can see different energy use. Frequent high-speed driving, steep terrain, cold conditions, climate control, towing and a heavy load can all affect how many kWh are needed per kilometre. If you are comparing models, use consumption figures on a consistent basis and treat them as estimates; your own journeys are a better guide once you have them.
A home tariff may vary by time, while a public charger may have a separate price and fee structure. Charging a small amount at a location with a fixed session fee can make the cost per kWh effectively higher. For budgeting, use the total amount charged for real sessions where available, not just the headline energy rate.
When assessing the extra cost of charging at home, distinguish electricity used by the car from fixed charges you would pay anyway. A daily charge on a household bill is not automatically an EV charging cost. However, if buying an EV leads you to change plans or install equipment, include any new or changed expenses that are genuinely part of your decision.
A practical estimate starts with your own driving pattern, not a full-battery calculation. Use these steps before buying an electric car or revising your household budget:
It can help to make two estimates: a typical month and a higher-use month with extra driving or more public charging. This shows whether the budget still works when your routine changes, without presenting a single precise figure as certain.
Charging is only one part of the running-cost picture. To compare an electric car with a petrol vehicle, estimate the energy cost for the same distance in each. For the EV, multiply grid energy per kilometre by the relevant electricity rate and add charging fees. For the petrol car, use its fuel consumption and the fuel price you expect to pay. Keep the distance and time period consistent.
Then consider other ownership expenses, including purchase or finance costs, insurance, tyres, servicing, registration and depreciation. These can vary substantially by model and driver. A lower charging bill does not by itself prove that an EV will cost less overall, just as a higher public-charging bill does not determine the total cost for a driver who charges at home most of the time.
If home charging requires installation work, include that as a separate upfront or financed cost rather than hiding it in the per-kWh estimate. If you rent, park on the street or share a charger, confirm access arrangements before assuming home-rate charging will be available. The charging pattern you can sustain is more useful than a theoretical low rate you cannot routinely use.
A larger battery can require more electricity for a full charge, but most drivers do not refill the entire battery each time. Regular running cost depends more on energy use per kilometre, distance travelled and the rates paid. Battery capacity is most useful for estimating the cost of a specific top-up.
Not necessarily. A vehicle display may report energy used by the car, while your bill reflects electricity drawn from the supply, which can be higher because of charging losses. Check the meaning of the figure or compare it with charging records that measure supply energy.
List the public or workplace chargers you can realistically access, then use their displayed tariffs and any additional fees. Estimate how much of your driving each option can support. If those chargers are inconvenient or limited, account for that in your decision as well as in the cost calculation.
Not necessarily. Check whether parking, time limits, access conditions or other charges apply, and consider whether reaching or waiting for the charger adds a cost or inconvenience. A free charging session also may not be available when you need it, so it may not be a dependable basis for your regular budget.
Update it if your electricity plan, driving distance, charging routine or public-charger tariffs change. Once you have an EV, actual bills and charging records can replace the assumptions used in your initial estimate. Rechecking periodically helps keep the figure useful for household budgeting.
To estimate the cost to charge an electric car, combine your likely distance, the model’s real-world energy use, your accessible charging options and their current rates. Treat examples as starting points, include losses and fees, and revise the estimate using actual charging records. That gives you a more useful ownership budget than relying on a single headline price.
