size solar energy system for electric vehicle

Solar Panels and Electric Cars: Can I Use Solar as an EV charger?

Solar panels and electric cars are a match made in heaven ­– when you install a solar energy system on your home, you can use it to both power your home and charge your electric car for emissions-free transportation. The cost of solar is falling rapidly, and companies from Tesla to Nissan are manufacturing electric cars for your daily use. Now, the ability to install a solar PV system large enough to power both your home and your car is an option within reach. But even with incentives and rebates available for both technologies, most homeowners still can’t afford to install solar and buy an electric car at the same time. Luckily, it’s easy to install a solar energy system today that takes your future electricity consumption into account, if you take a few additional factors into consideration.

Can you use solar panels to charge electric cars?

The simple answer is yes, a solar installation will charge your electric car just as it will supply energy for the rest of your home appliances. Even a small solar panel array with only 10 solar panels can provide enough power to charge your vehicle’s battery.

Solar electric car chargers: how much energy do you need for your EV?

Before you can make a decision on the size of your solar energy system, you need to determine how much electricity your car will use in the future. In addition to helping you size your solar energy system, knowing your electric car’s mileage rating can help you quantify the amount that you’re saving by switching to an electric vehicle.

Since electric cars don’t run on gasoline, the EPA rates them based on how many kilowatt-hours (kWh) it takes for the car to drive 100 miles, which they convert to a “miles-per-gallon equivalent” (MPGe). You can use to find and compare the kWh/100 miles and MPGe ratings for all of the electric vehicles on the market in the United States.

electric vehicles and solar

Once you know EPA’s fuel economy rating for your chosen vehicle, you can easily calculate how much extra solar electricity you’ll need to charge your car. Here’s an example: the 2014 Nissan Leaf, an all-electric vehicle, has a combined fuel economy rating of 30 kWh/100 miles – this means the Leaf requires 30 kWh of electricity to drive 100 miles. If you drive 25 miles on an average day, that means you’re using approximately 7.5 kWh of electricity per day – or just over 2,700 kWh of electricity in a given year. This is the “extra” amount of electricity you’ll need your solar energy system to produce.

Armed with this information, you can work with your solar installer to design a solar panel system that will generate sufficient power to cover both your home and your electric car. All you’ll need to complete the package is an electric car charger like the Siemens VC30GRYU Versicharge. But if you’re not ready to make the investment in both solar and an EV at the same time, you’ll need to install a solar PV system that can grow as your electricity use increases.

How many solar panels to charge an electric car?

First things first: don’t put off going solar just because you might want to get a bigger system in the future. If you wait to install solar, you could miss out on state and local financial incentives – plus, you’ll have to continue paying for electricity from your utility every month. By sizing your solar energy system for future usage and ensuring your system is “add-on friendly”, it’s easy to find an option that generates enough electricity to power your home today and can charge your electric car in the future. Here’s how to do it:

1. Install an inverter that can handle more power

The default option for inverters is known as a string inverter. With string inverters, multiple solar panels are arranged into “strings,” which feed the power they produce into a single inverter. Typically, solar installers will include an inverter that can handle the expected output of your solar panels, but no more. If you know how many more panels you’ll need to add to your system later on, you can install an inverter that can handle the capacity of your existing panels plus the new ones you plan on adding after purchasing your electric vehicle.

2. Install microinverters with your solar panels

If you opt for microinverters instead of the default string inverter, each of your solar panels will have its own inverter. With microinverters, you can easily add extra panels to your system down the line without having to worry about whether your existing inverter can handle the additional electricity your new panels will generate.

3. Install a second, smaller solar energy system

So long as you have enough space on your roof, you can add a second system to your home whenever you need it. Homeowners can claim the federal tax credit for solar more than once, so you’ll still save significantly on your purchase.

4. Determine your future use, and build a bigger system to match.

If you know that your electricity use will increase in the next year or two and have access to enough financing, you can build your solar energy system based on your future electricity use. This isn’t always an option – some utilities won’t approve systems that go significantly beyond your historical electricity use, so be sure to talk to your solar installer about your options first.

Another option is to “make room” later down the line by implementing energy efficiency upgrades to your home, which has the added benefit of reducing your overall energy costs. Consider switching out light bulbs, installing a programmable thermostat, or upgrading your appliances to free up some of the electricity your solar panels generate for future use in an electric vehicle.

It’s worth noting that the strategies above work not just for electric cars, but also for any other additions or changes you make to your house that will increase your electricity usage. If you’re considering adding an electric heat pump system, electric water heater, or an addition on your home, you can expand your solar energy system to take your future electricity use into account.

Tips for solar shoppers

If you’re thinking about going solar, it’s important to know all of your options – you can save up to 20 percent just by reviewing multiple offers. To get started, find out just how much you can save with EnergySage’s Solar Calculator, or register your property to start receiving custom quotes from pre-screened solar installers near you.

electric vehicles and solar

This post originally appeared on Mother Earth News.

21 thoughts on “Solar Panels and Electric Cars: Can I Use Solar as an EV charger?

  1. Jim Kadel

    For charging an electric car or hybrid plug-in, why not do it without A.C. conversion, for efficiency sake? i.e. electric solar panels develop D.C. and car batteries take D.C. so why not avoid inverters to do this job? It seems to me the d.c. to d.c. transfer of electrical energy would be the most efficient.

  2. Alkè

    Very interesting. EV’s are a great way to reduce air pollution and to sefaguard the environment. Adding the solar power to this, we can create a perfect “green” combo. Solar system are no more science fiction: there are state financial incentives!

  3. Chris Beard

    Hi Maria,

    I was thinking about your question, and may have some possible reasons:

    A car doesn’t have a lot of surface area or flat surfaces to easily install panels
    The area under the windscreen is very small, not nearly enough to produce enough energy to power a car or perhaps justify the installation cost
    The reflection from the panels or their casing may distract the driver
    The weight of panels may erode their value on a car (as you would use power moving them around)
    Panels outside the car need to cope with travelling at high speed and presumably must not impact the aerodynamics of the car or it could defect the object
    Solar Panels are not that cheap, and may increase the car cost so it is not competitive
    This very thing is being considered/done by Tesla on the Model 3 (the roof may be made of solar panels I understand) and is already an option on the Nissan LEAF for the spoiler (although for the LEAF I don’t think it actually charges the main battery)
    There is also another technology looking at another material for Solar Panels (perovskites) that may provide a cheap way to provide power from windows, by only absorbing a non-visible bandwidth of light via a thin film encased in glass. This might make more sense to be ‘in’ the windshield. This isn’t commercially available yet (and may never be)

    Hope this helps


  4. Andrea

    It seems portable arrays should be available to yard mount, mount on a carport. Having to address the home does not seem feasible in a world of changing priorities.

  5. Dev

    why don’t electric cars come with Solar panels on roof. It may keep batteries charged during day time.

  6. Ray Cardona

    After five years of solar panel ownership and two years of electric car experience, my best observation is that home solar panel installation”s purpose should be for home use, to draw down the power used from the grid. Electric cars do not use that much power to justify the expenses of a solar installation. Many EV owners without solar report a monthly cost of about $25 to $35, depending on the car and use. The Tesla cars are least efficient and yield 2.5 to 3.0 miles per kW hr. A new Hyundai Ioniq EV, sold in Europe, can travel 5 to 6 miles per kW hr. Even with the lower cost of solar in 2017 and federal and state incentives, where available, a $200 to $250 yearly electrical cost cannot justify solar expenses. However, our rather large and inefficient homes do need help. I got solar first, evaluated the power generated vs. past bills and it was a great benefit. Adding an electric car was just gravy, as, in my case, electric cost for the car are nearly zero nine to ten months of year.


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