Can you charge your EV from a home battery?

With the rising popularity of electric vehicles (EVs), and recently announced rebates for home batteries, many of our customers are asking if they can charge their EVs from a home battery.

The short answer is yes, but it's not always the best choice.

Here’s why.

Understanding battery sizes

Batteries installed in homes are typically much smaller than batteries in EVs.

For example, a standard home battery is around 10kWh. This is sufficient to power your house for a few hours.

Electric vehicles have much larger batteries, more than twice the size - often over 40kWh and up to 100kWh.

This size difference means that relying on your home battery to charge your car daily could quickly deplete the home battery. This would leave limited energy for your home use.

Over time, this will also degrade the home battery’s health and reduce its lifespan.

One option to address this is to purchase a larger home battery system. However, this can increase the cost enormously.

If purchasing a huge battery isn’t an option for you, here is the advice we give our customers.

Make use of optimal charging times

Instead of using your home battery to charge your EV, consider these more efficient charging strategies:

Daytime charging with solar power

If you have solar panels at home or at work, daytime is the perfect opportunity to charge your EV using the sun’s energy.

A solar installation soaking up the sun’s energy, feeding straight into an EV battery

This not only saves money but also maximises renewable energy use.

Even if you don’t have solar power, charging in the middle of the day means you’re making the most of solar power available on the grid. It is cheaper and environmentally friendly.

A few energy providers are now offering cheap (sometimes free) EV charging during the day to encourage daytime charging.

Off-peak night charging

If charging your car during the day isn’t an option, the next best choice is to charge your car from the grid later at night, after 10 PM.

Electricity prices drop significantly during off-peak hours, making it a budget-friendly time to charge up the big battery in your car.

This is a much more affordable option, and will leave your home battery to power your home during peak hours in the evening and early mornings, when the electricity price is high!

The role of smart chargers

Smart chargers are game-changers when it comes to optimising how and when you charge your EV.

Our Zappi EV charger, set to charge our EV using only solar energy.

Smart chargers can schedule charging sessions during off-peak hours automatically. This means you can just plug in and walk away.

These chargers are a great investment if you’re looking to make charging both convenient and cost-effective.

However, it’s really important to be aware that not all EV chargers will work well with home batteries.

It is also really important to make sure your EV charger installer understands how to install the charger correctly.

A good question to ask your installer is ‘will the charger discharge my home battery when my EV is charging, or will power come from the grid?’

If the installer cannot provide a clear answer it is best to find another installer.

If you’re based in Tassie, feel free to give us a call for advice and to discuss your options.

When to consider using your home battery to charge your car

There might be times when charging from your home battery makes sense.

For example, if you need to urgently charge your car when power prices are at their peak in the evening, usually between 5-7 PM.

If you need to charge your EV during this window of time - and can’t wait until later at night - tapping into your home battery could help you avoid those hefty electricity bills.

Just remember, it’s best not to make this a regular habit due to potential degradation of your home battery over time.

Conclusion

In conclusion, while it is possible to charge an EV from a home battery, it requires careful consideration of the alternatives and the long-term impact on your home battery.

By optimising your charging habits with solar, smart chargers, and off-peak rates, you can ensure efficient and sustainable energy use.