Want to drive totally off-grid? Here’s your guide to charging your electric car with the sun
Using the sun to charge your electric car is the ultimate way to close the loop on clean footprint motoring.
But while the charging may be ‘free’ in many ways, you need quite a bit of infrastructure and equipment to ultimately bid farewell to ‘the grid’. The upside here is that your car isn’t the only appliance that will benefit.
Here’s what you need to know…
Solar Energy basics
The basic principles of a home-solar system see your solar panels collecting energy during the day and pushing it through an inverter (solar systems are DC – direct current – where your home uses AC – alternating current) through the house and back into the electricity grid. For every kilowatt (kW) collected and fed into the grid each hour, you are ‘paid’ a rebate by the electricity company. This rebate is subtracted from your total electricity use which will reduce your bill.
Example:
Installing a 5kW solar system will (on a sunny day) push a maximum of 5kW of energy into the grid each hour for approximately 10 hours. This is 50kWh worth of energy, and at an average Feed-in Tariff (FiT) of $0.07 per kWh means you’ll earn a credit of $3.50 per day, or approximately $100 per month.
5kW x 10hr = 50kWh : maximum energy fed into the grid each day
50kWh x $0.07 = $3.50 : approx FiT rebate each day
$3.50 x 30 days = $105 : approx FiT rebate each month
However, given the average energy use by an Australian family house is 30kWh per day, the step between the solar inverter and the electricity grid – where you use the energy collected by the solar system, could mean your house runs entirely off the solar array. Happy days!
To save this energy, to use during the night, you can also install a battery where excess energy collected by the solar panels is stored until you need it.
Bottom line, the right solar system with a large enough panel array and a storage battery can mean your home is entirely self-sufficient.
The downside is this isn’t cheap.
Our 5kW example system will cost about $5000 to install. An 8kWh storage battery, enough to run 25 per cent of your daily household needs, will be about $12,000 (with an inverter). Add some labour and you’re looking at around $20k to set this up.
Compare this against the average Australian annual electricity bill of $1500, and you need to think about the long-term gain before you see any short-term wins.
Note though, that most states offer rebates and incentives to install solar, and if you are looking at a new build or renovation, this is a cost that could very easily be rolled into the total construction charges.
Charging an electric car at home
Adding an electric car into the mix doesn’t have to change the system complexity, as your home charger simply draws energy like any other appliance, it just ups the numbers.
On average, an EV will use 20kWh per 100km, and for urban use, will travel an average of 50km per day. This adds 10kWh to your home’s total energy use, stepping things up from 30kWh to 40kWh per day.
You can support this with a bigger (more expensive) storage battery, or work on the principle that every kWh drawn from the electricity grid requires about 3x that number fed in by your solar system to offset any costs.
eg: if your Feed-in Tariff is $0.07 per kWh but your average grid charges are $0.19 per kWh, you’ll need to push through about 27kWh of energy to the grid (rebated at $1.90) to offset the car’s 10kWh draw.
This method could see your bill still equalise, but you need to use the grid to charge your car as the power needs of an EV are so much more than that of your house. For context, fully charging a 73kWh Hyundai Ioniq 5 is equivalent to 2.5x your daily home use. Yikes.
Charging an EV using solar only
If you want to completely disconnect from the grid, you can add another device to your electrical system to ensure your car only uses solar to charge.
A smart charger can be configured to only use energy captured by your solar system. These cost around $2500 and would generally require more battery storage to work effectively, especially if you need to charge more than 10kWh each day.
Is solar charging worth it?
In the same way that choosing an electric car will not deliver an immediate cost saving, a solar charging system needs to be considered as a long-term investment.
For the spreadsheet to start to equalise, you need to think of solar as at least a 10-year proposition.
But if you are happy to invest in the infrastructure as part of your home’s capital value, then the right setup of solar panels and storage batteries can see you unplugging from the grid right now!
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