Common questions about using solar panels to charge an EV

06 Aug.,2024

 

Common questions about using solar panels to charge an EV

Charging an electric vehicle (EV) with free, clean energy generated from solar panels on your property is a win-win. Your solar panels offset some of the increased electric load of charging an EV, and you have the satisfaction of knowing that your vehicle is charging with renewable energy.

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Whether you have solar panels already or you&#;re planning to install them, there are several factors to consider if you want to charge an EV from your system.

Can an electric car be charged with solar panels?

Yes. The electricity produced by home solar panels can be used for any electricity needs in your home, from appliances to electronic devices to EV batteries. Generating your own clean electricity from solar not only lowers your energy bills and shields you from utility price hikes, but it can also drastically reduce the cost of running your EV.

How does solar EV charging work? 

Typically, solar panels are installed on the roof and connect to your home electricity supply through an inverter, which is usually mounted in a garage, basement, or utility room. But they can also be connected directly to an EV charger. These charges are usually close to where you park your car,  such as in a garage, carport, or driveway. 

Many electric vehicle chargers can be integrated with solar panels. The main consideration is the size of your solar energy system: Is it large enough to provide electricity to your home as well as an EV? If you already have solar panels, you may need to add a few extra to meet the increased demand from the EV. If you're planning to install solar, let your installer know if you have or plan to buy an EV.

How many solar panels do you need to charge an EV?

The number of solar panels you need depends on several factors, including where you live, how much energy your household uses, what direction your roof faces, and the type of solar panel you install. In general, however, it takes between seven and nine solar panels to charge an electric vehicle. It&#;s important to tell your solar installer if you plan to buy an electric car &#; even if it's not right away &#; so that they can correctly size your solar system and choose an inverter that can handle the potential increase in power output in the future.

Can you add more panels to an existing solar system to charge an EV?

Yes, provided you have enough space. It's a good idea to use the same panels you already have so that the power outputs and specifications match as closely as possible. It's also worth asking an installer to check whether any components, racking, or wiring needs upgrades, especially if you&#;ve had your existing solar panels for a while. 

Will charging an EV with solar save money? 

Yes, because electricity generated by your solar panels is free! You have to pay to charge your EV at a public charging station or from electricity supplied by your utility at home. The rates you pay depend on the charging station or your utility rate, which you can find on your bill in cents per kilowatt-hour (kWh).

How long does it take to charge an EV with solar?

An average electric car takes about eight hours to charge fully. Several factors influence charging time, including the size of the car's battery and its maximum charging rate, which is the rate at which the battery takes in electricity. There are also different types of chargers available, ranging from Level 1 chargers (the slowest) to Level 3 chargers (the fastest).

How do you charge an EV when your solar panels aren't producing power? 

The time of day and weather conditions will affect how much electricity your solar panels produce. On cloudy days or overnight, for example, your panels will produce much less electricity. You may need to supplement your solar power with electricity from the grid. 

You could also install a battery system to store the clean, free solar power that your panels generate. That way you can draw power from the battery when your solar panels aren&#;t producing electricity &#; say, if you want to charge your EV overnight. Battery storage allows you to maximize the benefits of your solar panels. 

Charging an electric car with solar panels makes so much sense. Whether you plan to install panels for the first time or expand an existing solar energy system, working with the right installer will ensure your solar system is correctly sized to charge your EV.

Panasonic&#;s network of vetted installers has the knowledge, tools, and experience to help you plan the best solar system for your home and electric car charging needs. Talk with an authorized Panasonic installer and get all your questions answered.

Top Questions About Solar EV Charging, Answered

Everyone knows that solar power is a highly sustainable source of electricity, and the cost advantages can be enormous. Beyond those two facts, however, questions abound. Here are answers to questions frequently asked by EV owners about solar EV charging.

(Image source: Energy Sage, via BuildWithRise.com)

How do solar charging stations work?

Solar panels convert sunlight into DC (direct current) electricity. A connected inverter changes the DC electricity received from the solar panels into the AC (alternating current) electricity needed for EV charging. The AC electricity goes to a distribution board to be used by power devices, and any surplus electricity is stored in a battery or fed to the grid for use by others. 

A smart EV charger takes the solar-generated AC electricity and charges your EV directly from the distribution board or a battery. The charger can use 100% solar power or a combination of solar and grid power to achieve the desired charging speeds. When AC power flows into your EV through the charging cable, your EV&#;s onboard charger converts it back into DC electricity.

What are the benefits of having solar EV charging stations?

Although most people think that the benefits of a solar EV charging station revolve around sustainability and cost savings, there are six primary benefits:

Energy Costs: Solar-generated electricity is almost universally less expensive to purchase than that obtained from any grid in the U.S. Many people find that their monthly power bills drop by as much as half.

Net Metering: Electricity generated by solar panels during the day can be pushed to the grid for credit against your power usage. If you can push more power to the grid than you use yourself, you can sell the surplus to the utility provider at a profit.

Zero Carbon Footprint: Between 40-80% of national grid power in the U.S. is still manufactured from fossil fuels and other non-renewable energy. However, a home solar EV charging station guarantees a 100% carbon-neutral footprint.

Convenience: Public charging stations can be inconvenient, particularly in areas that don&#;t have very many. Even a home-based station can be problematic if powered off the grid and there&#;s an outage. Home solar charging stations are the ultimate convenience and provide insurance against grid outages.

Tax Credits and Incentives:  There are several Federal, State, and Local tax credits and incentives for EVs, EV charging, and solar EV charging. Start your search with the U.S. Department of Energy&#;s Alternative Fuels Data Center.

Increased Property Value:  Studies show that homes with installed solar systems sell more quickly and at a higher price than homes that don&#;t. According to the National Renewable Energy Laboratory, home values increase by $20 for every $1 that a home solar system saves the homeowner on their electrical bills. The Zillow real estate website calculates that homes with solar panels sell for an average of 4% higher than those without them.

How can I charge my EV at home using solar panels?

Charging your EV with solar panels is more complex than just installing the solar panels on your roof and then plugging them into your car. You need a solar panel system designed for EV charging. A typical setup includes:

  • Solar panels mounted on your roof in metal racks 

  • A central

    string inverter

    combining DC output to AC, or micro-inverters that convert each panel&#;s output to AC and send it to a combiner box 

  • A Level 2 EV charger 

Many vendors specialize in installing home solar systems to power households and electric vehicles. Three better known include Freedom Solar (12 locations nationally), Sunpower Solar, and Sunnova (both servicing all 50 states). For DIYers, Electric City outlines a six-step process for installing a solar at-home EV charger.

(Image source: SolarTribune.com)

How many home solar panels does it take to charge an EV for daily use?

The exact number of panels it takes to charge your EV at home depends on four major factors:

  • How many miles do you drive on an average day

  • How many hours of sun do you get on an average day

  • The wattage of your solar panels

  • Your EV&#;s fuel efficiency

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You own a Tesla Model Y and drive it about 37 miles on a typical day. The rated fuel efficiency of a Tesla Model Y is 3.82 miles per kWh. The area you live in gets an average of 4.5 hours of sunlight daily. You&#;ll need to install six solar panels (each 400w) to provide the necessary power to charge your Tesla at home.

Say that, instead of a Tesla Model Y, you drive a Toyota RAV4. The Toyota has a rated fuel efficiency of 2.17 miles per kWh. With all other factors matching the Tesla example above, you would need ten 400w solar panels to produce enough power to charge your EV for daily use.

More information on calculating the number of panels needed to handle both home power needs and EV charging requirements is available at TheSolarNerd.com. 

How long does it take to charge an EV using solar panels?

Not surprisingly, the answer to this question varies significantly based on solar panel wattage, type of solar panel controller, battery AMPs, battery discharge depth, and more. 

For example, let&#;s say you are charging a 12V 50Ah lithium battery that&#;s 80% discharged. You&#;re using a 100W solar array with an MPPT controller. You need six peak sun hours to charge your battery fully. If your location gets three peak sun hours daily, you&#;ll need two days to achieve a full charge.

FootprintHero.com offers two handy resources:

  • A

    charging time calculator

    that determines the number of peak sun hours you will need for your specific parameters


  • A

    peak sun hours calculator

    that determines the average peak sun hours received by your location

(Image source: PiwinEnergy.com)

What&#;s the best time to charge an EV with solar panels?

You want to charge your EV at the time of day that maximizes both the financial return and environmental benefit of your solar panels. This time depends on whether you have a time-of-use (TOU) plan with your electric utility company or a Net Metering/Net Billing plan.

With a TOU plan, the rate homeowners pay for electricity depends on what time they use it. Rates are less during times of lower demand. Net Metering plans give solar homeowners credit for excess power they produce that&#;s dumped into the grid based on the retail rate. Another option, Net Billing plans, pay the homeowner based on the wholesale rate.

The best time to charge your EV is based on the type of plan you have. Here are the rules of thumb:

  • Net Metering plan with TOU

    &#; Charge during off-peak hours (usually overnight).

  • Net Metering without TOU

    &#; Charge at any time of day, but doing so during off-peak hours will minimize carbon intensity.

  • Net Billing with TOU

    &#;

    Charge during off-peak hours if the savings are greater than the difference between your retail and wholesale rate; otherwise, charge when your panels are producing power (while the sun&#;s out).

  • Net Billing without TOU

    &#; Charge when your solar panels are producing power.

Most late-model EVs can be set to charge automatically at a specific time, making it easier for owners to target lower-cost periods. If your EV doesn&#;t, you can buy an EV charger with a built-in timer.

What are portable solar panels for EV charging?

Portable solar panels for EV charging are small, lightweight options for EV owners who want to charge their vehicles at home without installing a permanent solar panel system. 

Portal panels are easy to install, needing little more than a connection between the panel and your EV battery. For that reason, you can charge your EV from anywhere you go using cheap, renewable solar energy. Like a permanent solar panel system, portable solar panels use photovoltaic cells to absorb the sun&#;s energy and convert it into electricity.

Light Tower Pro lists a variety of the best portable solar panels for EV charging. These include models by well-known manufacturers, including Bluetti, EF Ecoflow, Goal Zero, Jackery, Renology, and Rockpals.

What are off-grid solar EV chargers?

Off-grid solar EV chargers store solar-generated power in batteries for use on demand to charge electric vehicles. They do not require plugging into the grid.

Unlike portable solar panels, which are small and lightweight, off-grid solar EV chargers are usually close to the length and width of a full-size automobile, accompanied by a box-like structure containing the storage batteries.

The power generated and sold is usually less expensive than power purchased from the grid, especially during peak periods.

What are the best EV charges for solar panels?

Some of the highest-rated EV charges for use with solar panels are listed below, linked to Amazon listings where you can learn more about each:

(Image source: ChargePoint)

Interested in learning more about EV Charging infrastructure? Join us at the upcoming EV Charging Summit & Expo!

Featured Image by Freepik.

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