Energy consumption for charging an EV at home

People write in and ask me about charging Electric Vehicles at home, and also how to best optimise their home around charging an EV.

Let's take a quick look at a real home that recently bought an EV and see how it changed their consumption patterns and what they are thinking about next.

An EV will transform the energy consumption patterns of the home

Depending on the car, an EV will require around 10 to 20 kWh of energy for every 100km of driving range. If you drive quite a lot each day and charge your car at home, that can start to add up. Even if you're not driving that often but live a pretty energy-efficient lifestyle, an extra 20 kWh of energy consumption a week could still be a recipe for quite a shock when it comes to looking at your bills. I recently ran a battery analysis for a home in rural Victoria that had bought an EV. On their property, they also had an older solar system, so they were wondering whether to replace the whole system and get a battery or keep it as is. To figure out the answer, we ran our analysis to help answer their big questions. We were also able to see their energy consumption patterns before and after they bought the EV and started charging it at home.

The chart below shows the home's energy consumption before they purchased the EV, the dark green bars are energy consumption from the grid, and the light green is solar exports to the grid.

What we are seeing above is their consumption and solar exports averaged into a single day. The dark lines are their consumption, and the green lines are their solar exports, the excess they sold to the grid. This period is mostly winter 2024, so overall their exports are lower than the rest of the year.

Now lets take a look at the same home with the same setup but in same exact period but in winter of 2025, the only difference was they now had an EV in their home, occasionally charging every few days.

Before the EV, the home's highest average consumption was at around 5pm and peaked at around 1.25 kWh. Now their peak consumption is at 3pm and around 3.5 kWh. Their peak energy consumption on average is nearly three times higher, and it's earlier in the day. Needless to say, this home is due for an upgrade, but what kind of upgrade and how big is the next question they need to answer.

The effectiveness of your solar system and EV depends on your afternoon schedule

This won't be a huge revelation, but if the EV is home during the afternoon, then it can make the most of the solar energy and use it to charge the car. It's really then a matter of having an adequate solar system size to charge the EV and rely less on grid consumption to power your home and the car.

If an EV is home during the day, a well-sized solar system to charge the EV is ideal. The size of the system depends on the EV itself but ideally an EV can take the majority of the solar energy so it can be utilised later when driving around. In the case of the above home their EV is clearly there biggest power hungry device so it makes sense to try and optimise around its usage.

This homeowner had received a quote for a 6.6 kW solar system, so we looked at what the predicted solar production of a 6.6 kW system would do for them. We also examined how this would offset their current winter consumption overall given their current EV charging schedule.

In the graph above, we can see the difference a new solar system makes to the home's energy consumption. In this instance, upgrading to a 6.6 kW solar system is expected to reduce the EV's consumption over winter significantly. Though there would still be consumption on some days that sneaks through that the solar isn't covering. While it's certainly an improvement, there's still room for further upsizing on their solar. In this case, the home could consider installing a larger solar system to cover a greater portion of their energy consumption. While it will never be a perfect one-to-one for consumption and exports, they can get a better-suited system to do a better job more of the time. Also, note that this is winter consumption and production, so in Summer, their solar production will be much higher. We don't want to overdo it too much, so that they hit their export limits.

Once we've sized the system appropriately, later, if there is still excess solar energy available, a home battery can help the home capture the remaining solar power to reduce grid consumption later in the evenings.

In practice, this means your home battery’s utilisation is primarily for charging the home, and the frequency and depth of charging and discharging cycles dramatically improve. Rather than sitting idle, your battery can be used in moderation to charge your vehicle, even during energy spikes, increasing your savings and accelerating the return on your investment.

One crucial consideration for EV owners (or future owners) is choosing a modular battery system. Modular systems let you incrementally increase your storage capacity over time. Start smaller, and expand your system as your energy needs grow, especially as EV adoption accelerates. One note is that the new federal rebate is only available for your initial battery purchase. If you decide to upgrade the battery down the road, the extra capacity won't be eligible for a rebate.

Get your own analysis for your home

Unsure how your current system will work with a future home upgrade and if a battery is right for you? I can help you run the numbers and see if a battery makes sense for your home.

How it works is we remotely connect to your energy provider over the net, they send us your energy consumption and solar export history for up to years in the past! We then use all that data to simulate how a battery would perform in your home, charging and discharging hundreds of times a year.

The end result is that we can figure out what battery size is right for your home and roughly how much it's going to save you, based on your actual energy profile and current pricing. No more flying blind, taking the word of an installer who wants to sell you the largest battery they can fit in your home.

If you'd like a battery analysis, then reply to this email. The analysis does cost $129, but if you're going to spend $7,000 or more, you should research what to buy and how much that battery is expected to save you.