Solar & EVs: Is there a benefit to using them together?
In recent years, electric vehicles (also commonly referred to as ‘EVs’) have surged in popularity. Not only are EVs a more environmentally friendly alternative to traditional petrol and diesel-powered cars, but they’ve also been acclaimed to have an attractively low running cost. With that in mind, it’s no shock that people are flocking to get on the EV bandwagon.
As their name suggests, EVs run on electricity, meaning the question of ‘car charging’ quickly comes to mind. Should you charge it from the grid? Can your solar panels charge the car on their own? What’s the best, cheapest, and most environmentally responsible way to charge your EV? Today, we’ll explore whether you need solar if you have an EV, examining factors such as power usage, charging options, and compatibility with your home solar system.
The median price to fill up a tank of unleaded fuel in Australia is approximately $72. The average Australian drives about 31.2km per day, so heading to the petrol station for regular fill-ups can become financially inconvenient. Now, many Aussies have been searching for a different solution, and that’s where EVs come in. After all, imagine being given the opportunity to use your self-produced solar to charge your vehicle!
There’s no doubt you’ve passed a few EVs on your morning commute – in fact, in the first quarter of 2024 alone, over 25,000 EVs had already been sold in Australia. This is more than 8% of total vehicle sales, and is a 46% increase on EV sales for the same period in 2023. So, at this stage, it’s safe to say that EVs are fast becoming a new standard for Aussie commuters. But, when it actually comes down to saving on that $72 unleaded fuel fill-up, how do EVs compare? And further, is solar EV charging the way of the future?
Measuring an efficient EV
The energy usage (measured in kilowatt hours, or ‘kWh) of an EV can vary depending on a number of things including EV make and model, driving habits, vehicle efficiency, and terrain. But, let’s have a look at some general statistics to give you a rough understanding of your EV’s capabilities.
According to experts, an EV that is considered generally ‘efficient’ will consume under 13kWh per 100km driven (13kWh/100km), with consumption above 20kWh/100km being classed as ‘inefficient’. One of Australia’s best-selling and most popular EVs measures at about 14.4kWh/100km, which sits at a standard level. This vehicle has a nominal battery capacity of 60kWh, and a driving range of between 300 – 610km depending on terrain and battery size. Based on the average commute of 31.2km per day, this vehicle would consume roughly 4.5kWh daily. For the remainder of this blog, we’ll use this best-seller as our go-to example.
Of course, different EV makes and models will have their own statistics, which you can find in detail on websites like ev-database.org.
Charging options for EV owners
First, to charge your EV may require you to look into a specialised EV cable and charging box. You could also go ‘stock-standard’ or make the trip to a charging station. And, you can combine the ‘stock standard’ and ‘charging box’ approaches with home solar as well.
The charger you choose should be based around when you’ll be charging your EV. For example, if you are thinking about charging your EV with solar, and the only daylight hours you spend at home are over the weekend, you might like to look into a faster charger to help you make the most of your solar energy. But before we jump into detail on techniques, tips and tricks, lets break down the three main charging options for EV owners:
Level 1 Chargers:
Most EVs will come equipped with a standard 10-amp cable to plug into the wall at home, just like a normal household appliance. These chargers are considered Level 1 in terms of charging power. The thing with the ‘plug and charge’ approach is that it’s quite a lengthy process. In fact, according to Synergy, charging from a standard socket can take as long as 14 hours; with a completely empty battery taking even longer. With the sun’s peak hours providing far less than that, charging your EV from solar via Level 1 cable could likely require some power purchased from the grid – even if your solar is producing some power during the charging process. That said, many EV owners are comfortable with Level 1 chargers, and simply ensure they plug their car in for a few hours every night to ensure they’re all topped up for their morning commute.
Level 2 Chargers:
Australia’s best-selling EV that we mentioned earlier requires a Level 2 charger. Generally speaking, a Level 2 charger is considered a wall box (either single phase or three-phase) from 5kW up to 22kW. Wall boxes are a popular choice for solar aficionados who want to charge their electric vehicle at home, and they generally get the job done a lot faster than the standard ‘socket in the wall’ approach. Mostly, these plug into your home’s power supply and then send this power to your EV through a special connecter cable. With a wall box, an EV battery can go from empty to full within 4-hours. But you can expect to outlay a several-hundred to a few-thousand dollars to get a compatible wall box set up.
Taking it a step further, fans of the Level 2 charging approach could also consider Smart Chargers. Smart Chargers prioritise large loads (like charging an EV) when there is excess solar available and are also a very popular choice among EV connoisseurs. A Smart Charger would intuitively divert power to your EV when power prices are low, or when solar is being generated. Experts generally consider Level 2 chargers to be about 8 times faster than their Level 1 counterparts, giving homeowners a prime opportunity to take advantage of solar for their EV. </p><p>(Note: There used to be harsh regulations on EV charging in Queensland, for example, EV owners used to be restricted to a 20 Amp/4.6kW limit or controlled load tariff, while also being under the control of the network. Energy networks have recently rewritten their rules on EV charging in the Sunshine State as of late March 2024, allowing properties on a single-phase to charge at a full 7kW capacity, with the correct equipment installed.)
Level 3 Chargers:
There are charging stations (also commonly called ‘fast chargers’) at key locations in each Australian state. These stations fall into the category of a Level 3 charger, with a 50kW to 350kW capacity. A quick look shows many falling between 30c/kWh up to $1.80/kWh to charge your EV. Each charging station has its own pricing structure, making it a mixed bag.
As you can see, there are a few different charging options available to EV owners, each with their own intricacies. Due to the costs associated with using a Level 3 charging station, many EV owners opt to charge their EVs from their home solar, mainly due to the substantial cost difference. </span>Overall, the way you charge your EV can affect your power bill. So, we’ve gone ahead and put together a handy graph to help break it down for you: 
Graph data based on the following numbers: 36.4km driving distance per day, as per RACV; Fuel efficiency of 6.9L/100km as per The Guardian; EV efficiency of 14.4kWh/100km as per RACV; Average unleaded fuel cost of $1.93/L as per Drive; Charging cost of 25.3c/kWh as per Drive; Average Level 3 charging cost of 30c/kWh per EV Powerhouse; QLD average home electricity standard tariff of 25c/kWh as per Canstar; Average home electricity cost via solar soak of 6.6c/kWh as per Energy Australia.
Breaking down solar system size and charging times
If you’re not-so-keen on heading to a charging station, especially after seeing the cost breakdown above, hopping on the solar-charged bandwagon could be a good and convenient way to go. But are your solar panels up to the job? Let’s do a bit of the math:
Imagine you have an EV that consumes around 4.5kWh per day. If you can charge it at home during daylight hours using a standard Level 1 power outlet, it would take roughly 2.5 hours to fully recharge. During this time, the charger draws around 2 kW of power. A typical 5 kW solar inverter should easily handle this load along with other household appliances, especially if you have about 6.6 kW of solar panels (approximately 15 panels at 420W each).
However, if you’re only able to charge your EV on weekends, you would need to recharge approximately 35 kWh. Using a Level 1 charger, this would take around 17.5 hours, often requiring you to draw power from the grid at night. To optimise your solar energy usage, upgrading to a level 2 charger would be beneficial. A 7kW single-phase charger could fully charge your car in about 5 hours, while an 11kW three-phase charger would do it in approximately 3.2 hours.
Considering the 7kW charger scenario, if you aim to supply it solely from solar panels, you’d typically install a 10kW inverter (the maximum for single-phase setups in many regions). To maximise, you could install up to 13.3 kW of solar panels, which is typically around 31 panels (assuming an average rating of about 420W per panel). This setup would ensure sufficient solar power to cover both your household and EV charging needs effectively.
Conversely, if your battery efficiency is the same as Australia’s most popular EV at 14.4kWh/100km (equal to 6.94km/kWh), and assuming you drive that average 31.2km per day, you’d require about 4.5kWh daily to get your EV topped back up. If you’re using a Level 3 charger to add that 4.5kWh of ‘juice’ to your EV, at 30c per kWh (the lower end of the charging station average we mentioned earlier), you’d be paying about $1.35 each time. If you were to do that every day, and you’d be out of pocket $492 per year.
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So, do I need solar if I have an EV?
We’ve gone through a lot of facts and done a lot of math on solar system size, EV battery capacity, and charging options. But overall, what’s the best option for an EV owner? Do you need solar if you have an EV?
The short answer – you can absolutely benefit from having home solar and utilising it to charge your EV. That said, it is not something that you need, since it is possible to charge an EV at home with electricity purchased from the grid, and Level 3 charging stations are located all over the country for those who need them. But, if you’re not keen on driving out of your way to a charging station, or, paying the associated fees (either from a Level 3 station or from grid power), solar would provide the ability to utilise your home solar to get your EV topped up and ready for your commute.
To maximise the efficiency of your home-charged EV using solar power, it’s beneficial to have a robust solar array. Additionally, understanding peak solar times, your charging options (such as Level 1 or 2), and your vehicle’s capacity can greatly enhance performance. Plus, if you’re using a Redback Smart Inverter, Smart Hybrid or Smart Three-Phase Hybrid while charging your EV, you can utilise Redback’s Smart Load Control feature to charge the EV when there is excess solar available, to greater maximise your charging experience.
If you’ve got solar now, or you’re looking to install solar in the near future, it pays to keep in mind the power requirements of your EV, as well as your intended charging habits (i.e. will you charge daily, or on the weekend? Will you charge during the day, or at night? Do you intend to use a Level 3 station, or charge at home?). With this information in mind, you can make necessary adjustments to your solar array, or, be able to plan and prepare for a balanced solar-to-grid power ratio to ensure your EV is topped up and ready for your daily commute.
Can I use a home battery system to charge my EV?
Once you’re all set on your solar journey, you may find yourself considering battery storage. If you’re currently utilising your solar to top up your EV, you may also find yourself wondering if your battery’s stored energy can be used to top up your car. So, let’s take a closer look.
While EV batteries and solar batteries might seem like a logical pairing, the reality is a bit more nuanced. Home battery systems, typically around 10kWh in capacity, pale in comparison to the energy storage required for an electric vehicle, which ranges from 20kWh to over 100kWh in capacity (depending on make and model). That said, attempting to charge an EV solely from a home battery would hardly make a dent in its energy needs. But, that hardly makes home battery systems useless – it just makes them more suitable for another use in your home.
Home battery systems shine when it comes to powering your home during the night or during blackouts, especially when paired with solar panels. They offer independence from energy retailers, a potential dent in your electricity bills, a sustainable alternative to grid power, and a suitable backup to keep essentials running when it’s needed most.
For EV owners, utilising a home battery to power your home during on-peak hours, while charging the EV during off-peak hours, can be a smart strategy. This approach not only maximises the efficiency of your solar investment but also takes advantage of cheaper electricity rates when you need to buy from the grid. It’s also a more cost-effective and environmentally friendly solution compared to frequent trips to public charging stations or draining your home battery for minimal gains in your EV’s charge.
Overall, while home battery systems are not practical for directly charging EVs due to their difference in capacity, they play a crucial role in optimising energy usage at home and providing a ‘next step’ in your solar journey.
While not a solidified necessity, integrating solar into your EV charging setup offers numerous advantages, from reducing reliance on the grid to harnessing clean, renewable energy. Understanding your EV’s power requirements, charging options, and solar system capabilities is key to maximising efficiency and cost-effectiveness. Whether opting for Level 1 or Level 2 charging options, or travelling to a charging station; aligning these elements ensures a seamless fusion of solar energy and EV convenience.
As Australia propels into the age of the EV, coupling solar power with electric transportation presents an opportune moment to embark on a sustainable and cost-savvy journey forward.
If you’re keen to look into solar as a home-powered option for your slick new EV, get in touch with a verified installer. Make sure to mention how much you drive per day to your installer, so they can provide tailored recommendations for a solar array that will meet your EV charging needs.
