Guide to Charging Your Electric Car with Solar Panels


For many electric vehicle (EV) owners, finding a public EV charging station can be a nightmare, especially for those who live outside of major city limits. As a result, many owners consider installing an electric car charging port at their home so that they always have access to a charging port.

At-home charging ports draw from the existing electrical grid. The cost of pulling from the electric grid is the same amount as any other household electricity. Because of the size and amount of electricity needed to charge an EV though, the cost of the at-home port will be dramatically high.

As a result, many people opt out of installing their own EV charging port. Little do they know that there is a way to make at-home charging ports more affordable: solar panels.

Solar panels are a great way to charge your electric car. They are affordable and great for the environment. Before installing solar panels for your EV at-home charging port, it is important to consider a few factors like the number of panels required, EV battery size, panel efficiency, etc. Let’s get started.

How Do Charging Port Solar Panels Work?

Using solar panels with an EV charging station is one of the best eco-friendly and cost-efficient options for charging your EV. Here’s how charging ports with solar panels work based on their installation process:

1.    Install Solar Inverters

Before you can use energy from the solar panels, the energy must be converted from direct current (DC) to alternating current (AC). The best way to convert DC to AC is with solar inverters.

Solar inverters are designed to handle the power of a solar panel. Installers typically choose string inverters, which arrange the solar panels into “strings” that feed the produced power into a single inverter.

Typically, the installers select inverters that can handle the expected output exactly. If you plan to add more solar panels later on, make sure that the installed inverters can handle the expected output once you add more panels.

An alternative to string inverters is microinverters. Microinverters allow each solar panel to have its own inverter. This will allow you to add more solar panels in the future without having to worry about the energy capacity of the installed inverter.

2.    Determine Future Use

To install the correct inverters and number of solar panels, you need to determine the future use of the panels. This includes increased future electricity use, additional panels, etc. If you do not plan for future use, you may have to pay more to fix your solar energy system down the line.

Unfortunately, some utilities will not approve a system that plans for more electricity than is historically used. So, make sure to talk to your installer about rules and regulations to work out the best option beforehand.

3.    Install At-Home Charging Port

Once you have installed the inverters and planned for future use, you can install the at-home charging port. You will need to attach the charger to the inverter so that the charger can draw from the solar energy captured by the solar panels. Once the charging port is attached to the inverter, the port will be able to transfer the energy from the solar panels to your electric car.

How Many Solar Panels To Charge An Electric Car?

As you are installing your solar panels and EV charging port, you need to determine how much energy you will need. If you have never done this before, estimating the needed energy can be difficult, but it doesn’t have to be. Here is what you need to consider for estimating your port’s needs:

1.    Electric Car Battery Size

The amount of energy your port needs is determined by the EV’s battery capacity. The port needs to be able to fuel the entire battery, or else the port will be inefficient at charging your EV.

An EV’s battery is measured in kilowatt-hours (kWh) and can range from the low 20s to over 100 kWh. The battery size will depend solely on the make and model of your electric car. So, be sure to research your EV’s battery capacity.

2.    Number Of Solar Panels

Once you know your battery’s size, you can move on to deciding how many solar panels your port needs. The number of solar panels is determined by the battery’s capacity; larger batteries need more solar panels while smaller batteries need fewer solar panels.

Additionally, the number of solar panels you need to charge your electric car is determined by the amount of energy that a single solar panel can produce. The material, size, and efficiency all affect the amount of energy that a single solar panel can produce.

Let’s say that you own a Tesla Model S and need to charge it from 0% to 100% capacity each day. Additionally, let’s say that your solar panels only produce 1 kWh a day. You would need 75 solar panels to produce enough energy to charge your electric car completely.

Luckily, most people do not need to charge their EV from 0% to 100% every day. In fact, most drivers only need to use 12 kWh of electricity a day, which requires 12 solar panels that produce 1 kWh each.

Additionally, the more effective your solar panels are, the less you will need. In the example above, we used the minimum amount of kWh to provide a conservative estimate. Many solar panels will produce more than 1 kWh a day.

On average, a 250W solar panel produces 30 to 42.5 kWh per month. Additionally, most EV charging ports will only need 6 to 12 solar panels, depending on the EV battery size and solar panel efficiency.

When Is The Best Time To Charge My EV?

If you have gone through all the trouble to install an EV at-home charging port with solar panel functionality, chances are you want to charge your EV using as much solar energy as possible. Though you might think that you can charge your EV any time you like, you should create a charging schedule that maximizes your solar electricity.

Your charging schedule should be determined on whether you have a net billing, net metering, or a time-of-use plan with your utility company.

Net Billing And Net Metering

Net billing is when you are paid the wholesale rate for excess electricity, which is the same rate your utility company charges. Net billing incentivizes you to use solar electricity, which requires you to use your electricity during the day. 

Obviously, this is a challenge for most EV owners since they charge their cars in the evening. Many EV owners with net billing try to conserve their car battery for the weekend, which will allow them to charge the EV all day long on their days off.

In contrast, net metering is when you get full credit for the energy you send back to the grid. This will allow you to charge your EV during the evening or in the morning.

Time Of Use Billing

Time of use billing (TOU) is when there are peak hour rates for the use of electricity. In other words, you get better deals on electricity if you use electricity during off-peak hours. TOU billing can be implemented in conjunction with either net billing or metering.

Why Don’t EVs Come With Built-In Solar Panels?

At this point, you may be wondering, “Why don’t car producers simply install solar panels onto EVs?” It seems like a great idea. After all, the EV would be charging almost constantly, allowing you to save energy and money.

Technically, EVs can have built-in solar panels, and some new models have solar panels in their designs (like the Lightyear One).

Unfortunately, most cars require too much energy for in-built solar panels. For an appropriate amount of power, cars would need either extremely efficient solar panels or multiple solar panels. Most solar panels aren’t powerful enough to power a car, however, and cars often do not have enough surface area to host the appropriate amount of solar panels. 

Thus, it is more efficient to charge an EV than it is to add an in-built solar panel.

Final Thoughts

If you want to add a solar energy system to your home, you need to plan for whether or not you will install an EV at-home charging port down the road. At-home charging ports require a large amount of energy, which means that you will need several high-functioning solar panels.

If you do not plan for your at-home charging port, you will find that it costs a lot of money to reinstall inverters that can handle the capacity of solar panels. Additionally, you may need to add several more panels, which will also cost a lot of money.

Though installing an EV at-home port with solar panels for energy can cost a lot of money upfront, it is important to remember that this energy will save you money in the future. To estimate the exact amount of savings you can make from solar panels, you will need to do your own analysis based on the number of cars you drive and the amount of sun exposure your area has.


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