We often engage with homeowners exploring the world of solar power, batteries, and their seamless integration with electric vehicles (EVs). As we reflect on the incredible evolution of the solar industry in Australia over the past few years, it’s clear that achieving a home fully equipped with both energy storage and electric vehicles is a significant milestone.

We’ve compiled some helpful information to assist you on this journey.

Calculating Solar Panels for Your Electric Vehicle

Have you ever wondered how many solar panels your home needs to support an electric car? Before diving into specifics, let’s distinguish between a kilowatt (kW) and a kilowatt-hour (kWh).

Like the “L per 100 km” metric for petrol cars, electric cars have their equivalent: “kWh per km.” 

While this figure varies among EVs, the average electric car covers approximately 5-6km with 1kWh of electricity. For the typical Australian driver covering 42km daily, an electric car requires around 7-8kWh for a full recharge.

A 1kW solar capacity (equivalent to approximately three panels) yields an average daily output of 4kWh, varying with seasons. To offset the charging needs of a daily-driven electric car, consider adding around 2kW of solar panels to your roof. However, additional factors must be considered, so let’s delve deeper.

Click here to learn more about the difference between a kW and a kWh.

Round Trip Efficiency and Charging Losses

Remember that charging losses exceeding 10% due to inefficiencies between solar panels, inverters, and car batteries should be anticipated. If your solar panels generate 1kWh, only about 900Wh will end up in the EV’s battery pack. Consider installing more solar panels than initially estimated to compensate for these losses.

New Home Construction: Single-Phase or Three-Phase Power?

For those building new homes, three-phase power is worth considering. Three-phase power allows for a more extensive solar array to reliably support a futuristic home with high electricity demands, including a household battery and one or more electric vehicles.

Charging Your Electric Car with Solar Power

Charging your electric car with solar energy is a straightforward process. Simply plug your car into your home’s EV charger during daylight hours when the sun shines. No grid electricity is necessary if the solar electricity generated matches or exceeds the car’s charging requirements and other household loads. Yet, grid electricity may supplement the shortfall on cloudy days with minimal solar power.

Remember this as we cover special EV energy rates and smart charging devices below.

EV Charger Levels Explained

Understanding the three levels of electric car chargers—Level 1, 2, and 3—is essential.

Level 1 charging is the slowest, utilising a standard 10-amp power point and adding approximately 12 kilometres of range per hour.

Level 2 involves a specialised EV charger, providing a charging rate of 7kW and adding around 40 kilometres of range per hour on single-phase or 130km on three-phase.

Level 3, or rapid charging, is conducted using dedicated public chargers, such as the Tesla SuperCharger, capable of adding up to 720 km of range per hour.

It’s important to note that not all electric vehicles can fully utilise Level 3 chargers, and overusing them may impact the vehicle’s battery life.

Battery Storage for Night Charging

While it’s feasible to charge a home battery system during the day with solar power and then use this stored energy to charge an electric car at night, be aware that such heavy usage can impact the solar battery’s lifespan. Technological advancements are improving this aspect, but losses between solar panels, home batteries, and EV charging should be acknowledged.

Special EV Rates & Smart Charging Devices

A better way to charge your car overnight is to explore some of the special EV rates offered by energy providers that might negate the need for larger solar systems to power your car. These rates are designed for overnight charging and can be as low as $0.08 per kWh.

Charging your battery from the grid overnight allows you to keep the battery storage for home use, potentially reducing the need for much larger systems.

When pairing these special EV rates with an EV smart charging device, you can take full advantage of your setup by only using excess solar energy during the day to charge your car, eliminating the risk of your car demanding energy from the grid. The remainder of the car’s charging needs can be scheduled to coincide with when the special EV rates are available to you.

This approach keeps charging costs to a minimum and makes you less reliant on solar power for charging your electric car so that low solar days don’t inflate your energy bills.

Final Considerations for Solar & EVs

When determining the solar power system size for your electric vehicle, factors such as the EV’s make/model, driving habits, and household energy usage must be considered.

While an average Australian driver may require an additional 2kW of solar power, your actual amount will come down to your driving habits and energy needs.

Installing as much solar capacity as reasonable is advisable, especially for households envisioning a future with multiple EVs and a sizable battery. And, while special EV rates are attractive now, they may not always be that way, so future-proofing your system so that it can grow with your needs is essential.

If you’re looking at getting an electric vehicle, solar, or both, talk to one of our experts to ensure you get a system designed to meet your specific and unique needs.