Using an EV car battery to power a home

At the time of writing, February 2018, it has been advertised that the new Nissan Leaf electric car, which is to be available on the Australian market mid year, can be used to feed electricity back into a home battery. So, can the car serve as a home battery as well as a vehicle?

It seems that you would still need some sort of home battery, but perhaps you could go for the Enphase battery for $2000 instead of the Tesla Powerwall for $8750. The Tesla Powerwall can store 14kWh, the combination of the Nissan Leaf, with a 24kWh battery, combined with the Enphase batter, 1.2kWh, gives a total energy storage of 25.2kWh.

This can make the economics of buying an electric car look far more attractive.

This page written 2018/02/21 – ©
Contact: email daveclarkecb@yahoo.com (David K. Clarke)

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The Nissal Leaf is expected to be sold in Australia for around $50,000. A similar sized car powered by an internal combustion engine (ICE) can be bought for about $20,000; there are virtually no government incentives for electric vehicles (EVs) in Australia.

How can paying two-and-a-half the price for an EV be justified? What are the factors involved?

  • For those who care about the environment, minimising the greenhouse emissions that they are responsible for in particular, EVs do not burn fossil fuels and do not emit greenhouse carbon dioxide;

  • For those who have solar power (16.5% in Australia and getting on toward twice that in two states, Queensland and South Australia) an electric car can be much cheaper to run than an ICE powered car;

  • If the car battery can also serve as a home battery the value of the EV can be substantially increased.
The costs of the home batteries discussed on the Gizmodo Home Battery Storage Buying Guide at the time of writing varied from $2000 to $10,000 while their capacities varied from 1.2kWh up to 14kWh. As an example, if the 24kWh battery of the Nissan Leaf could be combined with a low-priced, low-capacity battery such as the Enphase 1.2kWh product it could avoid the need of buying a high-priced, high-capacity battery such as the Tesla Power Powerwall 14kWh product. The combination of EV and small home battery would give a far higher energy storage capacity for the home than would the Tesla PowerWall alone.

Of course there are other factors to be taken into account; for example:

  • Power from the EV battery will only be available while the car is at home and connected to the home power supply;

  • If a substantial part of the power from the EV is used in the home the amount remaining to power the car will be reduced correspondingly;

  • Energy will be lost in transferring power from one battery to the other;

  • Increased frequency of charging and discharging of the EV battery will shorten its life.
There have certainly been many exciting developments in power technology in the last few years and decades.