Solar EV Charging: Daytime Solar vs Off-Peak Night Rates

You have got solar panels on the roof. You have got an EV in the driveway. You should be saving a fortune, right?

Maybe. But there is a surprisingly common mistake that eats into those savings: charging your car at night when you could be charging it for free during the day.

It sounds like a small detail. It is not. The difference between daytime solar charging and off-peak night charging can be $500+ per year. For some households, it is the difference between solar paying for itself in 4 years or 7.

With EVs accelerating in Australia (BYD expanding to 15 countries with vehicles like the Shark pickup, Toyota ramping up its electric lineup, and new home builds now routinely including EV charging and solar as standard wiring considerations) this question is going to matter to a lot more people very soon.

Let us look at the actual numbers.

Here is the fundamental problem. When your solar panels produce more than your house needs during the day, that excess gets exported to the grid. Your retailer pays you a feed-in tariff for it, typically 3-8 cents per kWh across most of Australia right now. Some retailers are offering as little as 0-5 cents.

Then at night, when you plug in your EV, you buy electricity back from the grid at 25-35 cents per kWh. Sometimes more on peak tariffs.

You are selling low and buying high. Every single day.

Think of it like growing tomatoes in your backyard, selling them to the supermarket for 50 cents a kilo, then buying them back that evening for $3. You would not do that with tomatoes. But a lot of solar owners are doing exactly that with electricity.

A solar owner shared their full year of data online, a 6.7kW system with an EV. The results were eye-opening.

Their electricity cost dropped to 43% of what it would have been without solar. Good, but not great. The reason? Only 36% of the solar they generated was actually used by the household. The other 64% was exported to the grid at a fraction of the import price.

The owner knew exactly why: they were using 300-400 kWh each month to charge their EV, and they were doing it at night. No solar involved. They admitted they could optimise by charging during the day, but said “it's just easier to do it at night.”

Let that sink in. They were exporting thousands of kWh of solar at around 3.6 cents per kWh, then importing a similar amount to charge their EV at 11-13 cents per kWh. Even with relatively cheap off-peak rates, the convenience of night charging was costing them roughly $300-400 a year in lost savings.

Their conclusion? “I need to get batteries.” And someone responded: “For your setup, batteries would help way more than adding extra panels.”

Self-consumption is the percentage of your solar generation that you actually use yourself, instead of exporting it. In Australia right now, with feed-in tariffs at historic lows, self-consumption is the single most important metric for getting value from your solar.

Here is how the numbers typically stack up:

Here is what each charging strategy actually costs per charge. We are using a 50kWh charge as the benchmark, roughly a full charge on something like a Tesla Model 3 Standard Range or BYD Atto 3.

If you charge twice a week from daytime solar instead of off-peak grid, that is roughly $780 saved per year. Compared to peak grid charging, the saving is over $1,800 per year. Over the life of your solar system, that adds up to tens of thousands of dollars.

And here is the kicker: that “free” solar electricity was going to be exported at 5 cents per kWh anyway. So it is not just that you save $7.50 per charge versus off-peak. You also stop losing the export revenue gap. The true value per charge from solar is the avoided import cost minus the lost export credit, and with feed-in tariffs this low, the avoided import cost dominates.

Daytime charging is not always realistic. Let us be honest about that.

If your car is parked at work all day and only home in the evening, you cannot charge from solar no matter how much you want to. There are some scenarios where off-peak night charging is genuinely the right call:

You do not have to manually watch your solar app and sprint to plug in the car every time the sun comes out. Smart chargers can do this automatically, and they range from simple timer-based options to full solar-aware systems.

The biggest objection to daytime charging is simple: “My car is at work during the day.” Fair enough. But for many households, the picture is more nuanced than that. Here is how to capture as much solar charging as possible.

What if your car is genuinely at work all day every day? That is where a home battery changes the equation.

The concept is simple: your battery charges from excess solar during the day while your car is away. When you get home in the evening, the battery feeds that stored solar into your EV charger. You are still effectively charging from solar, just time-shifted.

There is some efficiency loss, roughly 10-15% through the battery charge and discharge cycle. So a 50kWh charge might need 55-57kWh of solar generation to account for that. Still vastly cheaper than buying from the grid.

And the battery does double duty. It covers your household evening usage too, which means you are not buying expensive peak electricity for the house either. Some owners take it further with battery arbitrage strategies that charge at low spot prices and discharge during peaks. One investment solving two problems.

When you put it all together (solar panels, a home battery, and an EV with smart charging) you get something close to energy independence for both your home and your transport.

Here is what a typical day looks like:

Australian feed-in tariffs have been dropping for years. What used to be 44c/kWh in some states is now 3-8c in most places. Some retailers are offering as little as 0-5 cents, and in some wholesale windows prices even go negative. The economics are screaming one message: use your own solar, do not export it.

Meanwhile, grid electricity keeps creeping up. The gap between what you get paid for exports and what you pay for imports has never been wider. Every kWh you self-consume, whether it is running the dishwasher, powering the aircon, or charging your EV, is worth 3 to 5 times more than exporting it.

An EV is the single biggest load-shifting opportunity in most households. It is a giant battery sitting in your driveway that needs to be filled with electricity. Filling it from your own solar instead of from the grid is probably the highest-value thing you can do with your excess generation.

Add to that Australia's abundant sunshine, high electricity prices, and one of the highest rates of rooftop solar in the world, and the case for solar EV charging is stronger here than almost anywhere.

If you have solar and an EV, daytime charging should be your default. Not night. Not off-peak. Daytime.

Every kWh that goes from your roof into your car instead of being exported at 5 cents and bought back at 30 cents is a small win. Multiply that by 300-400 kWh a month and the small wins add up fast.

If your car cannot be home during the day, a battery bridges the gap. If you do not have solar yet, an EV is one of the strongest reasons to get it. The combination is where the real savings stack up.

Stop selling tomatoes for 50 cents and buying them back for $3. Your roof is growing more than enough.

Ready to see how the numbers work for your home? Take our rebate eligibility quiz to check what incentives are available in your state, or explore our full EV charging with solar guide for charger recommendations and sizing advice.