Complete Guide To Charging Electric Cars With Solar Panels

If you want to save money on driving while also shrinking your carbon footprint, using solar panels to charge an electric car can be a great option. But how do you set up the right combination of solar panels, inverters and electric vehicle charging equipment?

This article will help answer these questions for homeowners who have:

• An electric vehicle (EV) but not home solar panels
• Solar panels but not an EV
• Neither solar nor an EV but an interest in both

Let’s break down some fairly technical concepts into easy-to-digest information that can help you plan a lower-emissions future and potentially save money. We’ll also compare home solar charging for two popular EVs.

The Big Question: Can Solar Panels Charge Electric Cars?

Simply put, solar panels can charge electric cars. Companies such as Beam Global manufacture commercial solar installations where EV drivers can charge using renewable energy as they shop, dine or work.

The average home solar installation can also charge vehicles using clean energy. A grid-tied home could directly power EVs during the day or use grid power to charge overnight when rates are usually cheapest, which we’ll cover in more detail shortly.

Is It Cheaper To Charge An EV At Home With Solar Panels?

Even if you don’t have home solar yet, it’s more convenient to charge an EV at home. Like plugging your cell phone, you wake up to a full charge. There’s no need to stop at a car-charging station.

It’s often cheaper, too. While some public EV charging stations are free, most charge a rate based on time or kilowatt-hours (kWh). For example, the Blink charging network charges 39 cents to 79 cents per kWh for public Level 2 stations in areas that allow per-kWh pricing. In other areas, Blink charges 2 – 3 cents per 30 seconds, depending on the state and whether the customer is a Blink member. Compare that to the national average residential rate of 13.66 cents per kWh of electricity.

Solar homeowners may pay even less than that, especially when charging overnight. Some utility companies offer rate plans for EV charging and solar generation.

Why Many EV Drivers Charge Overnight

Many utility companies encourage overnight EV charging with low overnight rates. There’s less demand overnight, but utility companies are still running their power plants to provide a base load of electricity, so prices may be lower than daytime rates. As EV adoption increases, one Stanford University Study suggests we could see a shift toward more daytime charging incentives, especially in states that produce more utility-scale solar energy during the day.

How Many Solar Panels Does It Take To Charge An Electric Car?

If you’re wondering how many solar panels it takes to charge an EV, consider the following factors. Some areas receive more sunlight than others, making each kW of capacity go further. Therefore, it’s possible to have two 6-kilowatt photovoltaic (PV) arrays with different numbers of panels. Also, some panels are more efficient than others.

In addition, you’ll need to consider the size of your car battery. For example, a 6-kW system in sunny Arizona could produce 25 – 35 kWh of power daily. Electric vehicle batteries range in size from about 17.6 kWh for a Smart EQ Fortwo to 100 kWh for a Tesla Model X.

Charging a Model X equipped with a 100-kWh battery from 50% – 100% of its battery capacity would require 50 kWh, not including the power needed for the rest of your home.

Pros And Cons: Should You Use Solar Panels To Charge An Electric Car?

Wondering about the pros and cons of charging your EV with a home solar array? This chart shows them at a glance:

How Long Does It Take To Charge An EV At Home?

It’s not easy to say exactly how long it takes to charge an EV at home. This depends on a number of factors, including:

• The size of your EV battery and the maximum rate of its onboard charger
• Your Electric Vehicle Supply Equipment (EVSE), which plugs into your vehicle to provide electricity
• The voltage and amperage of the circuit for your charging system
• How much electricity your EV needs

Let’s discuss these in more detail.

Battery Size And Onboard EV Charger

The bigger your battery, the longer it will take to charge if all other things are equal. Your vehicle’s onboard charger converts alternating current (AC) to direct current (DC) that its battery can use to drive the motor. Onboard charging rates vary. So, for example, a 2014 Nissan LEAF has a 6.6-kW onboard charger, while a Tesla Model Y has an 11.5-kW charger.

EVSE

People might refer to Electric Vehicle Supply Equipment (EVSE) as a car charger (which isn’t accurate), a charging cable or a charging station. Some are portable and can fit in your car, while others can be hardwired into your home.

There are three types of EVSEs:

• Level 1: Most EVs come with a portable Level 1 EVSE. They can plug into a 15- or 20-amp 120-volt outlet, just like the regular outlets in your home. They’re slow, though, adding just 1.4 kWh – 1.9 kWh per hour. It’s possible to find a basic Level 1 EVSE on sites like Amazon for less than $200.
• Level 2: Many EV owners buy a Level 2 EVSE to get faster charging at home. Level 2 equipment can be portable or permanently attached to your home, and it requires a 240-volt circuit rated at 15 to 80 amps. Level 2 EVSEs can add 3.3 kWh – 6.6 kWh per hour. Some are programmable so you can charge during specified times, and they may even have Wi-Fi. A recent Car and Driver article reviewed Level 2 EVSEs that ranged in price from $320 to $1,249.
• Level 3: Also known as DC fast charging, your car will need a DC onboard fast charger to use this equipment. Level 3 devices add as much as 200 miles of range in 30 minutes. Typically, DC fast charging isn’t feasible for homes. You’ll usually see it at charging stations along highways or other well-traveled areas.

Circuit Amperage And Voltage

EV owners often choose Level 2 EVSEs for home charging that’s faster than the Level 1 EVSE that came with their vehicle. This usually requires installing a dedicated 240-volt circuit, as mentioned above, and is similar to the circuit required for a dryer or washing machine. 

Higher amperage allows faster charging. If you plan to be a multi-EV household, consider the higher end of the amperage options. The cost for adding a 240-volt line depends on the EVSE’s distance from your home’s electrical panel, the amperage you choose, and other factors. Prices can range from $300 – $800, not including the cost of the EVSE.

How Much Electricity Your Car Needs

If your car uses gas, you probably fill it up and then drive it until it’s nearly empty. EV drivers tend to “top off” more often. This can make charging for your daily needs require less time.

Upgrading Your Current Solar Panel System For EV Charging

If you installed your solar panel system before buying an EV, your installer likely designed the system around your energy needs at the time. With an EV, you’ll offset less of your electricity consumption with clean energy. Consulting a solar installer to increase your production could be a solid move. Here are some questions to ask:

Can your inverter handle more solar production?

String inverters can only convert so much DC to AC. If you add panels to increase your production, you might need a more powerful solar inverter. If your system uses microinverters, adding more panels is a bit simpler.

Can you switch to more efficient panels?

There’s a problem with adding to your solar panel installation: Your roof might not have the space. But if you have older, less efficient solar panels, you can consider upgrading to more efficient PERC solar panels. You could also make a move from polycrystalline to monocrystalline panels. Contact your solar installer to understand what’s feasible.

Can you add a home battery?

Adding solar battery storage may also require a new solar inverter. That’s because batteries usually store electricity as DC, while inverters convert DC to AC. A qualified installer will be able to assess your situation.

Building A Solar System To Charge EVs

Thinking about going green? Adding solar panels and driving an EV will reduce your carbon emissions – and save you money in the long run.

Be sure to discuss your plans with your solar company. The installer and their installation team will be able to ensure you get a solar panel system that meets your needs.

Accommodating an EV or two in your solar household may cost a bit more. Microinverters are often more expensive than string inverters, but they make it easier to add capacity to your PV system as needed.

You might also need to add more panels than a typical household or opt for high-efficiency panels that increase your upfront costs.

There are also solar batteries to consider, which could make you more independent from the grid while charging overnight.

Vehicle Comparison: Tesla Model 3 Long Range And Nissan LEAF

Wondering how long it takes to charge two different EVs at home? The chart below compares vehicles that contributed to early electric car adoption. The Tesla Model 3 and the Nissan LEAF are among the most common EVs on roads nationwide.

* Based on the U.S. average electricity rate of 13.66 cents per kWh

FAQs: Using Solar Panels To Charge Electric Cars

Here are a few questions from solar homeowners about making the switch to EVs.

Should I always charge to full capacity?

Some experts say keeping your EV’s battery at 20% – 80% is the best way to keep your battery in top condition. Some EVs and programmable EVSEs allow drivers to charge to a specific percentage.

Is DC fast charging bad for EVs?

It’s best to use DC fast charging only when necessary. Slower charging is currently better for battery longevity.

Do I need a solar battery to charge overnight?

If you have a grid-tied solar home, you can charge your EV overnight using power from the grid. If your home is off-grid, though, you’ll need a solar battery to ensure you have enough electricity for all your needs. 

Are there incentives for installing home EV charging?

It’s possible to find incentives for home EV charging equipment. The recently passed Inflation Reduction Act of 2022 extended the Alternative Fuel Refueling Property tax credit to December 31, 2032. This federal tax credit can allow eligible homeowners to claim up to 30% of the cost of installation and hardware from their tax return. Consult a tax professional to see if you qualify.¹

You can find state and local incentives at the NC Clean Energy Technology Center’s Database of State Incentives for Renewables & Efficiency^®.

How many kW of solar are needed to charge an electric car?

In most cases, you’ll charge at night. This means drawing from your electric company as long as your home is grid-tied. There’s really no minimum solar array size required to charge an electric car unless your home is off the grid. In that case, you’ll need to consider your energy consumption, your home’s battery size and how much you’ll charge your car each day.

What happens if I use more power than my solar panels produce?

Homeowners with solar panels sometimes consume more electricity in a day than their system produces, especially in the summer. This isn’t a problem for grid-tied homes, which simply get extra energy from the grid. At other times, solar homes produce more energy than they need and send extra energy to the grid. Many homeowners are even compensated for excess power through a billing system called net metering.

If you have an off-grid home, you’ll need enough solar power to cover your daily needs. Using batteries can help you store energy to use if your solar array doesn’t completely meet your energy needs. 

The Bottom Line: Solar Panels Are A Low-Cost, Eco-Friendly Way to Charge Electric Cars

Driving an EV and charging at home using home solar panels can help you use fewer fossil fuels and save money. Today’s solar panels are more capable than older panels of providing the energy you need. Even if you have to use some power from the grid, you’re still cleaning up your local grid and roads.

Ready to power your EV with sunshine or future-proof your solar installation? We’re ready to help. Talk with a solar advisor today.

¹Rocket Solar does not provide legal or tax advice. The information herein is general in nature and should not be considered legal or tax advice. Consult an attorney or tax professional regarding your specific situation.