EV Home Charger Payback Calculator NZ
This calculator works out how quickly a home EV charger pays for itself, by comparing the cost of charging at home against using public chargers. Buying an electric vehicle is only the first decision; how you charge it makes a real difference to running costs. A dedicated home charger, or wallbox, costs money to buy and have installed, but charging at home, especially overnight on a cheap or off-peak electricity plan, is far cheaper per kilowatt hour than using public fast chargers, which carry a premium for their speed and convenience. The question is how long the savings take to recover the install cost. This tool answers it. You enter the cost to buy and install the home charger, your annual driving distance, your EV's energy use per 100 kilometres, your home electricity price, and the typical public charging price. The calculator works out the energy your driving needs each year, the cost of supplying it at home versus from public chargers, the annual saving from charging at home, and the payback period, the time for those savings to cover the install cost. The results update as you type, so you can test different driving distances and power prices. Use it to decide whether a home charger is worth installing, to compare charging options, or to estimate your EV running costs. The more you drive and the bigger the gap between your home and public charging prices, the faster the payback. Many drivers find a home charger pays for itself within a couple of years, after which the savings keep adding up. A simple wall socket trickle charge is cheaper to set up but much slower than a dedicated charger.
Payback = install cost / annual saving. Saving = (public price - home price) x annual energy used. The bigger the price gap and the more you drive, the faster the payback.
How it works
The energy your driving needs each year is the distance divided by 100, times the energy used per 100 kilometres. Multiplying that by your home power price gives the home charging cost, and by the public price gives the public cost. The annual saving is the difference, and the payback period is the install cost divided by that saving.
Worked example
Driving 12,000 km a year, an EV using 18 kWh per 100 km needs 2,160 kWh. At a home price of 28 cents that costs about $605, while public charging at 80 cents would cost about $1,728, a saving of roughly $1,123 a year. A $1,500 charger therefore pays for itself in about 1.3 years.
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