A guide to solar power and electric cars for homeowners

The advancement of technology in the solar panel industry in Australia in the past decade has led to increased curiosity from homeowners about solar power, batteries, and how they link with electric vehicles (EVs). The real pinnacle of solar energy usage is having your home fully equipped to store solar energy and to integrate an electric vehicle into your fully-electric home to fully divest from the coal and gas industries.

It was recently estimated at an incredible 1 in 5 of all premature deaths are partially the result of air pollution, so a transition to EVs run on renewable energy is going to be a huge step forward for Australia’s health, and of course for the environment.

Solaray is excited to be leading Australia’s transition to renewable energy one household at a time, and in this guide, we’ll gather and answer the most commonly asked questions about the topic.

How many panels are needed on my home to provide enough energy for an electric vehicle?

First, we need to understand the usage of kilowatt-hours [kWh]. This is different from a kilowatt [kW]. As with the ‘litre per 100km’ measurement which tells us the average amount of fuel used to drive a petrol car 100km, electric vehicles use a different unit of measure to show the distance they can travel on 1kWh.

This figure differs depending on each electric car, but, generally speaking, most EVs get around 6km of range per 1kWh of electricity they store in their battery pack. So, if Australian’s drive, on average, 50km each day, the EV would require around 8kWh of electricity to fully charge up the battery pack.

Around four solar panels (1kW of solar capacity) will generate a daily average of 4kWh of electricity over a year, with more being generated in summer and less in winter. Therefore, installing about eight solar panels (or 2kW of solar capacity) on your home should provide the 8kWh needed to charge up an electric vehicle that drives about 50km each day.

More detailed information on this is available here: How many solar panels to charge an EV?

What Does A 5kW Solar System Look Like

Why does 1kWh of solar energy not mean 1kWh of EV charge?

You may want to consider installing extra solar panels to meet your electricity requirements as efficiency losses can be higher than 10%. So, for example, around 900Wh of energy will reach your car’s battery pack if your panels produce 1kWh of electricity. This discrepancy is because of inefficiencies between inverters, your electric vehicle’s batteries, and the solar panels.

When is the best time to charge my electric car?

If you’re charging your EV using your rooftop solar panels, it’s easiest to have the vehicle plugged into the house during daylight hours when the sun is out. When the solar energy being produced is more than what you are using in the home, the excess solar power can be used to charge your vehicle.

Do remember, though, that if the solar energy being produced is less than the amount needed by the electric vehicle (for example, on a cloudy day), electricity from the grid will be used to top up the shortage. You will then need to check your energy tariffs as some households in Ausgrid pay different rates depending on the time of day:

Time of use billing tariffs NSW Ausgrid

Do I need battery storage to charge my EV at night?

The answer is no; you don’t. It is not likely to be cost-efficient to use solar power to charge a home battery during daylight hours, and then use this stored power to charge an EV at night. You’re likely to get better value by selling your excess solar-generated energy to the grid for a ‘feed-in tariff’, which is paid by your energy retailer as a credit on your power bill, rather than opting for a controlled load tariff to charge your electric car from the grid.

Environmentally, charging your vehicle overnight with electricity that is off-peak, and selling your solar energy to the grid during daylight hours is a good choice. The surplus solar energy that you’re sending will offset electricity that is generated by fossil-fuels.

Should I choose single-phase or three-phase power for my newly built home?

Consider future-proofing your home and choose three-phase power. This will let you install a much larger solar array (10kW is the average for a new home) that provides a reliable amount of power to your home. Long term you are likely to have increased energy needs when you eventually incorporate a household battery and an electric vehicle (or two).

What’s the difference between Level 1, 2 and 3 EV charging?

The chargers used for electric vehicles are split into three different charging levels (‘levels’ 1, 2 and 3), and only ‘level 1’ charging uses the standard power point in your home.

‘Level 1’ charging uses your regular home power points but gives the slowest charging rate. It will give around 20km of range to an EV every hour (though this will depend on the vehicle), so 10 hours of charge from a ‘level 1’ charger overnight can provide about 200km of range to your vehicle.

Charging at ‘level 2’ means you will need a specialised EV charger installed in your house. This can provide over 40km of range each hour. It costs around $2,000 to get one installed (but can vary a lot), and there are many brands of electric vehicle chargers on the market. Note that your vehicle’s manufacturer might require you to have a level 2 charger to keep the car in warranty.

‘Level 3’ charging uses specific public charge points for rapid charging. The most famous example is probably Tesla SuperChargers. These are generally used by those travelling longer distances, or when batteries run out of charge en route. These rapid chargers can add a considerable 400km of range each hour.

However, not all-electric cars are equipped to use the full output of the ‘level 3’ chargers. If you’re planning to go on a long trip using ‘level 3’ charge points, ensure that your vehicle is compatible.

Charging away from home. How should I cope with “range anxiety”?

Unlike a petrol car, which can be refuelled at any petrol station in a matter of minutes, even an electric vehicle that is using a ‘level 3’ charger, can take an hour to be fully charged (and will take much longer using a ‘level 2’ or ‘level 1’ charging point).

‘Range anxiety’ encompasses the considerable length of time it takes to charge an electric car and the scarcity (at the moment) of ‘level 3’ rapid chargers. It is the fear that your vehicle won’t be able to charge fast enough to get to your destination as scheduled, or won’t have enough charge to get there.

However, ‘range anxiety’ fears can be blown out of proportion. Most cars now have trip planning functionality that helps you plan a longer trip with scheduled stops at recognised charging stations.

As long as you plan in advance and stick to the car’s suggested journey plan, it’s improbable you’ll be caught with a flat battery. The current solution for some households is to have two cars, using a backup petrol car if the electric car battery is flat or for longer journeys.

Caravan parks can also provide ‘level 1’ charging with 15 amp power points if you get caught short with no ‘level 3’ chargers nearby. Some businesses and showgrounds also have publicly advertised EV charging points (though with others, you may have to ask politely if you can use their charging points).

Deciding on solar power for your electric vehicle

When you’re thinking about the number of solar panels needed to support an electric vehicle, there are several factors you need to consider. These include:

  1. The usual driving habits of the EV drivers, particularly the average daily distance you will drive
  2. The make and specifications of your electric vehicle – Tesla batteries, for example, are far large than most other EVs
  3. How much energy your household uses, and plans to use in the future
  4. The fact that an average Australian EV requires around installed 2kW of solar power to counterbalance daily driving usages

After now having helped thousands of households prepare for an all-electric future with battery storage and EVs, we recommend households install around 10kWs of solar power as a minimum. Solar power is now so cheap that you can install a large system and still see a fast return on your money even if you send a lot of excess electricity to the grid. Even if you don’t install a battery right now, the feed-in tariff is still high than the cost per kWh of your solar system, so you can take your time and install a battery along with your new EV when you are ready.

Solaray is recognised as the number one solar power installer in Australia by the world’s leading solar companies including LG Solar and Enphase. We can help you install a quality solar system that is future proof, plus, if you are ready to take the plunge, we can help you with battery storage and the transition to living an all-electric lifestyle including a plug-in hybrid or electric car.

Contact our experts today for advice and pricing:

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